Category: Science

Introduction

The chemical symbol for barium chloride is (\(BaC{l_2}\)). It has the appearance of a white salt but is actually an inorganic chemical complex. It gives flames a yellowish-green colour and emits poisonous fumes. It readily absorbs or absorbs water molecules, and may thus cling onto them. As a rule, it dissolves more readily or more easily in water. There is only cautious usage of it in labs and factories due to its toxicity. It has no discernible odour or hue in its pure form. 

What is Barium Chloride (\(BaC{l_2}\))?

The empirical formula for barium chloride is \(BaC{l_2}\). The only solvents that work on it are water and methanol, whereas ethanol and ethyl acetate have no effect. To purify the salt water used in caustic chlorine production plants. Sometimes, it is used in the manufacturing of heat treatment salts, which are used in the process of hardening steel.

Its extreme toxicity is shared by the majority of other barium salts that dissolve in water. It changes the colour of a flame to a bright yellow-green. Its molar mass, or molecular weight, is 208.23 g/mol in its anhydrous form and 244.26 g/mol in its dihydrate form (in dehydrated form). About 3.856 g/cm3 is its density. Barium chloride may be dissolved in the methanol, but not the ethanol or the ethyl acetate. When it is dehydrated, it takes on a shape that is similar to an orthogonal structure.

Structure of Barium Chloride \(BaC{l_2}\)

The anhydrous form of barium chloride has a crystal structure that is orthorhombic, while the dehydrated or monoclinic form is extremely unusual. Barium chloride (\(BaC{l_2}\)) is the ionic compound of  \(B{a^{2 + }}\) cations and \(2C{l^{-}}\)

anions. 

Barium chloride

Preparation of Barium Chloride

Following is the possible methods for the preparation of Barium Chloride (\(BaC{l_2}\))-

Barium sulphate is reacted at high temperature with coke to give barium sulphide.  

The barium Sulphide is further reacted with dilute hydrochloric acid as follows:

Properties of Barium Chloride \(BaC{l_2}\)

Some of Barium Chloride’s most fundamental characteristics are as follows:

• it takes the form of a white solid, although it can also take the form of a white salt
• Barium chloride has a melting point of about 960 °C.
• It dissolves in water and methanol but not in ethanol or ethyl acetate (EtOAc)
• Barium chloride’s molecular weight is 208.23 g/mol (for the anhydrous form) and 244.26 g/mol (for the dihydrate form) (in dehydrated form).
• The density of barium chloride is approximately 3.856 g/\(c{m^2}\) (in anhydrous form)..
• Barium chloride has a boiling point of roughly 1560 °C.

Uses of Barium Chloride \(BaC{l_2}\)

1. For the most part, barium chloride is used in caustic chlorine factories to remove impurities from brine solutions.
2. It is employed when carbon steel has to be hardened.
3. In addition, it is used in water purification.
4. The production of barium chromate, oil lubricants, and similar products all benefit from its presence.
5. Purification and the production of salts for thermal processing are two further applications.
6. In addition, it is crucial to the creation of some barium salts and a few dyes.
7. It may also be used to detect sulphate ions in a sample.
8. In the fireworks industry, it’s used to make the crackers a vivid yellow-green colour.

Chemical and Physical Properties

Chemical Properties

When we mix a solution of barium chloride with sodium sulphate, we get a twofold substitution reaction. A white precipitate, consisting of barium sulphate, will appear at the bottom of a test tube after the reaction. The diagram below illustrates the ionic reaction formed by this reaction.

The binary chlorine salt barium chloride readily interacts with water, as is well known. It forms NaCl-like ions when it dissolves in water. It doesn’t have any effect on the solution’s pH because of its neutral behaviour. The following is a response to that:

Physical Properties

• As stated in this article, Barium Chloride (\(BaC{l_2}\)) has an orthogonal crystal structure when anhydrous and a monoclinic structure when dihydrate or dehydrated.
• It has a white crystal-like appearance and a molecular weight of 208.23 g/mol (anhydrous) and 244.26 g/mol (hydrous) (in dehydrated form). The anhydrous form has 3.856 g/ml density, whereas the dehydrated form has 3.098. It melts at 963 °C and boils at 1560 °C.
• Barium chloride dissolves well in water and methanol but not in ethanol or ethyl acetate.

Health Hazards Caused due to Barium Chloride

Barium Chloride’s main health risks are:

• Barium chloride’s high toxicity limits its application in industry and labs.
• Barium chloride’s toxicity causes eye, skin, and mucous membrane irritation.
• Inhaling, swallowing, touching, or absorbing it might cause unconsciousness.
• Poisonous barium chloride can damage the kidneys, heart, and brain.
• Aquatic life is at risk.

Summary

Barium chloride (\(BaC{l_2}\)), an inorganic chemical compound, is a white solid or salt. Like barium salts, it is very poisonous. Water and methanol solubility.

It becomes yellow-green towards the flame. We then covered industrial or commercial barium chloride structure and processing. Its many uses include brine or saltwater purification, wastewater treatment, steel case hardening, and more. Finally, we addressed Barium chloride’s physical and chemical features and health risks.

Frequently Asked Questions

1. Is barium harmful to ecosystems?

Very little of these chemicals are preserved in this form after being released into the environment. Insoluble barium compounds have a longer lifetime in the environment and are usually harmless. The two most frequent forms of barium in nature are barium sulphate and barium carbonate, both of which are present in both soil and water.

2. Can barium be inhaled without risk?

A tiny amount of barium sulphate is safe for the lungs to absorb. Barium sulphate can disrupt pulmonary ventilation and perfusion, leading to symptoms including dyspnea, hypoxemia, acute respiratory distress syndrome (ARDS), and mortality if an excessive amount is inhaled or ingested.

3. As an electrolyte, why is \(BaC{l_2}\) so powerful?

\(BaC{l_2}\) is an ionic chemical that dissociates in water to produce ions and conduct electricity. Ionic bonding produces this salt. When electrons are shared between two atoms, an ionic connection forms.

Also Read this article on Barium Carbonate

Introduction

Molecular formula of barium carbonate This substance belongs to the class of inorganic chemicals. This has no aroma or flavour at all. It is a white salt that, like most other alkaline earth metal carbonates, is weak bases in water solution but soluble in most acids (except sulphuric acid). To put it another way, it is one of the most economically or commercially significant barium compounds. While insoluble in tap water, it dissolves somewhat or only partially in carbon dioxide-rich water (\(C{O_2}\)). When combined with other ingredients, it makes a potent rat poison. Other industries that put it to use include those that produce pigments, clay, polymers, plastics, etc. It’s also a key ingredient in making glasses of varying refractive indices.

What is Barium Carbonate?

The chemical formula for barium carbonate, an inorganic chemical substance, is (\(BaC{O_3}\)). In terms of flavour and smell, it’s completely neutral. It looks like regular table salt, just like the other carbonates of alkaline earth metals. It dissolves poorly or not at all in water, although it does so partially in water saturated with carbon dioxide . It also dissolves in most acids, including nitric and hydrochloric acid, but not sulphuric acid. The mineral form of this is known as witherite, and it occurs naturally. Many industrial and commercial applications exist for it. It’s a crucial barium chemical, actually.

Physical Properties of Barium Carbonate

Som physical properties of barium carbonate are-

• It is insoluble in pure water but it is soluble in the water-saturated with Carbon dioxide (\(C{O_2}\)) and it is soluble in most acids except sulphuric acid.
• It has a specific heat of around 0.1448.

• It generally appears as white crystals or white salt powder.
• It has an atom complexity of around 18.78.

Chemical Properties of Barium Carbonate

Some of barium carbonate’s chemical characteristics are as follows:

• Barium carbonate readily reacts with soluble calcium salts to generate Barium sulphate, which precipitates out of the solution, and calcium carbonate. Here is the chemical reaction that occurs while doing so:-

• Barium carbonate can also react with hydrochloric acid to precipitate out as  Barium chloride(BaCl), with by-products being water and \(C{O_2}\). 

Barium Carbonate Structure

      

Barium Carbonate

As seen from the above diagram, \(B{a^{2 + }}\) cation is bonded to the \(CO_3^{2 – }\) anion through an ionic bond. 

Various Uses of Barium Carbonate

Barium carbonate has a variety of applications, including those listed below.

1. As it has been discovered to be an insoluble white salt, it finds extensive application in the ceramics sector, where it is utilised in the production of many different kinds of ceramics.
2. Moreover, it is crucial in the production of PTC thermistors, capacitors, and other electronic devices, as well as the increasingly popular electronic ceramics.
3. Moreover, barium carbonate is used in the creation of fibre optical glasses and magnetic components.
4. It is also a key ingredient in the production of other barium compounds, such as barium oxide and barium peroxide.
5. A common method of producing rodenticide also involves barium carbonate (rat poison). It looks like flour or salt, which is probably why rats are drawn to it.
6. Barium carbonate has several commercial uses, including in the oil-drilling industry, photography, enamel production, magnetic material production, paint and brick production, and a wide range of chemical processes.

Production Method of Barium Carbonate (\(BaC{O_3}\))

Common production methods are:

Carbonation Method– In this process Barium Sulphide (BaS) is pulverised at high temperature. The reaction takes place as follows:

Poison Nepheline Conversion Method– In this method witherite is reacted with an ammonium hydroxide along with ammonium carbonate. The reaction takes place as follows: 

Metathesis Method– In this method barium sulphide and ammonium carbonate react to form barium carbonate through metathesis. The chemical reaction is represented as– 

Dry Granulation Method- Here, barium carbonate is sourced from overabundant precipitation, which is then sieved and stored in a raw materials warehouse.

Summary

Inorganic chemical compound barium carbonate is a  white crystalline powdered salt. Its molecular formula is \(BaC{O_3}\). It has no discernible taste or smell and no visible hue. In addition to being soluble in carbon dioxide-saturated water and the majority of acids, besides sulphuric acid, it may also be dissolved in pure water. It is important in various commercial industries such as polymer, dyes, paints, etc. Moreover, it is crucial in the production of PTC thermistors, capacitors, and other electronic devices, as well as the increasingly popular electronic ceramics.

Frequently Asked Questions

1. What makes barium carbonate so dependable?

Among common carbonates, barium carbonate has the highest heat stability. A metal’s electropositive nature tends to grow as it moves towards the bottom of the group of alkaline earth metals. As a result, they become more stable at high temperatures. The stronger the influence of the positive ion on the carbonate ion, the smaller the ion must be.

2. Does barium carbonate have any negative effects on the ecosystem?

As barium is insoluble in water and readily combines with other elements found in nature, like carbonate and sulphate, it presents minimal danger to humans and animals. Persistent barium compounds are often found in surface soil as well as the sediment of freshwater soils.

3. Would barium rust if left exposed to the air?

Barium is an odourless, silvery-white metal at room temperature that becomes a silvery-yellow tint when exposed to air. While it cannot be burned, it may break down when heated, releasing harmful chemicals.

Introduction

There are two types of acids, concentrated and dilute, both of which are defined by their concentration. Dilution occurs when an acid has a significant amount of water added to it. As such, they are diluted to lower the overall acidity. We stay away from the very dangerous acids. In addition, we pay special attention to acids because they may be kept in the home for regular use. Also, they are employed in the control of several chemical operations.

What are Acids?

To be considered acidic, a substance must have a sour flavour when dissolved in water, change the colour of certain indicators (like blue litmus turning red), react with certain metals (like Fe) to release H+ions, react with bases to generate salts, and speed up chemical processes. Acids can be either inorganic (such as nitric and phosphoric acids) or organic (such as phenolic and sulfonic acids) molecules. When these compounds are dissolved in water, the H atom(s) they contain are released as positively charged H+ions.

Examples of Acids

Examples of acids include the following:

• Arrhenius acid
• Citric acid
• Hydrochloric acid
• Sulfuric acid
• Acetic acid
• Vinegar

What is Dilute Acid?

If an acid has been diluted, it has lost more of its acidity to water than the water has gained from the acid. It does not weaken acid or reduce its reactivity. The acidity of the solution you’re working with will decrease. Dilute acids include sulfuric acid that is just 5 percent concentrated. The concentration of sulfuric acid in a solution of 100 grams of water is five percent.

Properties of Dilute Acids

Some common properties of acids are:

• There is a sour aftertaste while consuming acid.
• Electrical solutions are formed when water and acids are mixed together. All of the anionic charge is lost when strong mineral acids are dissolved in water. When organic acids are dissolved in water, a mild ionisation occurs. Some molecules are still in the process of joining together. They are referred to as weak acids.
• When exposed to acids, the litmus indicator changes from blue to red.

Chemical Properties of Dilute Acids

Hydrogen gas is created when metals react. Get some zinc flakes and place them in a clear test tube. Fill the test tube with a solution of HCl that has been diluted. The reaction produces a gas. A burning splitter is moved extremely close to the mouths of the test tubes in order to examine hydrogen gas. A popping noise can be used to detect the presence of hydrogen gas.

Salt & water are produced when an acid reacts with a base (metallic oxide).

When acids react with sodium hydroxide, salt and water are produced.

Altering the pH of the reaction environment can cause profound changes in the products generated from two extremely specific reagents.

Examples of dilute acids

Dilute Hydrochloric acid

Hydrochloric acid, often known as muriatic acid, is an aqueous solution of hydrogen chloride. The chemical symbol for dilute hydrochloric acid is HCl. The solution lacks colour and has a distinct aroma. Hydrochloric acid is a strong acid. It is a part of the stomach acid of most animals, including humans. Hydrochloric acid is a crucial reagent in many different industries and fields of study. Dilute hydrochloric acid refers to aqueous acid mixes in which the concentration of HCl is lower than that of water.

HCl molecule

Dilute sulfuric acid 

Sulfuric acid is a mineral acid made up of H2O and sulphur. Sulfuric acid has the formula\({H_2}S{O_4}\). Sulfuric acid is also known by the name “oil of vitriol,” which is a synonym. It is a thick liquid that is both odourless and water-soluble. With its hygroscopic properties, it swiftly soaks up moisture from the air. The aqueous form of sulfuric acid is a powerful acid.

Dilute acetic acid

Ethanoic acid is the official word for acetic acid. \(C{H_3}COOH\) is the molecular formula. It’s an acidic, odourless, and colourless organic molecule. Vinegar contains just acetic acid and water, with the acetic acid accounting for at least 4% of the liquid content. Acetic acid ranks as the second simplest carboxylic acid. The hydrogen in the centre of the carboxylic group is ionisable by carboxylic acids like acetic acid (COOH). Due of this hydronium ion release, acetic acid is acidic. Disappointing monoprotic acid quality.

Summary

Hence, acids are compounds that, upon contact with a base, give forth hydronium ions. Protons are donated to the body by acids. pH values below 7 are considered acidic. Substantial volumes of water are found in diluted acids. A concentrated acid can be diluted using water. A lot of hydrogen ions are released into the water when a strong acid is used. Inorganic acids such as sulfuric, nitric, and hydrochloric acid are examples of strong acids. These substances are called weak acids because they only dissociate into a small number of hydrogen ions when dissolved in water.

 

Frequently Asked Questions

1. What is the procedure of dilution?

Ans. Acid is always poured into the water and not the other way around during dilution.  When \({H_2}O\) is combined with an acidic solution, the \({H^+}\) ion concentration decreases, and the solution’s pH rises. The acidic strength then starts to weaken and it becomes diluted. 

2. Are diluted acids as hazardous as concentrated acids?

Ans. Although dilute acids are considerably less hazardous than concentrated counterparts, they are labelled with a warning that they could cause mild health problems or skin irritation. This makes sure that if one of them touches your skin, it will get red or blister.

3. How are dilute acids conducting in nature?

Ans. Dilute acids have free ions in the solvent. These ions carry charge from one electrode to another on application of potential and conduct electricity.  Aqueous HCl solutions can generate energy. Diluted acid produces fewer ions and conducts electricity less.

Introduction 

Ordinary substances like table salt are examples of binary compounds. Rock salt structure refers to the crystalline arrangement of salt. Sodium and chlorine ions are organised in a lattice pattern, which is made visible by this structure. Sodium and chlorine ions form a binary system in the sodium chloride lattice. It is essential to learn about these binary compound structures in order to comprehend the characteristics of various materials. Improved elasticity, strength, conductivity, and other physical qualities can be achieved through the synthesis and manufacturing of new materials in this branch of chemistry.

Structure of Sodium Chloride

What are Binary Compounds?

Binary compounds are those that consist of two distinct components combined together. Element refers to a material that cannot be chemically reduced to a simpler form. The simplest class of molecular compounds are the binary compounds. To further distinguish them, we might call them binary phase compounds or just binary phases. These compounds are crucial as they are used as building blocks in the production of several other key organic and inorganic chemicals. Water is an example of such a crucial substance. \({H_2}O\) consists of hydrogen and \({O_2}\), which are the two elements that may combine to form water. Water is a V-shaped covalent binary molecule. Two hydrogen atoms are covalently bonded to an oxygen atom with two lone pairs of electrons, making up a water molecule.

The Naming of Binary Compounds

Naming a binary compound is the same as naming any other kind of chemical. In the IUPAC system, you’ll find:

• To identify which cation is present in a binary compound, the cation’s name comes first.
• Binary compounds have their anion names written after the cation names.
• If you add the suffix -ide to the anion’s name, you get the element’s name. For instance, fluoride is the name for the fluorine anion.
• Among these, iron (II) oxide (FeO) is one example. Because iron’s oxidation state is +2, a roman number representing two is appended to the cation’s name.
• If there are more than two of each element in a binary complex, the ion count of each element is included in the ion’s name.
• Dinitrogen trioxide (\({N_2}{O_3}\)) is one such example. The prefix “di” is added to nitrogen because there are two of the element, while the prefix “tri” is given to oxide because there are three of the element’s oxygen atoms.
• When a binary compound contains a transition metal cation, the oxidation number of the cation is shown after the cation’s name in Roman numerals.
• Potassium chloride, for instance, is abbreviated as KCl. In this situation, potassium is a cation and chloride is an anion.

Examples of Binary Compounds

Covalent binary compounds-

Such compounds contain atoms of two elements joined by covalent bonds:\({N_2}O\) ,\(CC{l_4}\) ,\({H_2}{O_2}\), \(C{H_4}\), etc. 

Ionic binary compounds –

Such compounds contain ionic bonds that link atoms of two elements : NaCl, MgO, NaBr,\(BaC{l_2}\), etc. 

Transition metal binary compounds-

AuI, \(FeC{l_2}\)2, CuI, Lead (II) fluoride, \(PbC{l_2}\)2, etc. 

Binary Acids

Binary acids, also called hydracids, consist of hydrogen and a non-metallic element.  There are two types of acids: oxyacids and binary acids. Oxyacids are compounds made up of hydrogen, oxygen, and sometimes additional elements as well. The prefix “hydro,” followed by the element name, and then the suffix “ic” are used to name binary acids. Hydrochloric acid (HCl) is one such chemical. The primary building blocks of hydracids are hydrogen and halogens. Many parameters, including the bond energy of bonding between anion and hydrogen, the solvation energy of anion, anion electron affinity, etc., determine the potency of these acids. The hydrogen-ion connection is weaker in acids because hydrogen is a more electronegative element.

Difference between Binary Acids and Binary Compounds

Binary Ionic Compound

Binary ionic compounds are those that consist of atoms of two different elements bound together by electrostatic repulsion. For example NaCl, \(BaC{l_2}\), etc. These compounds form conduction solutions because of free moving ions. 

Summary 

In chemistry, the fundamental building blocks are binary compounds. Learning about larger molecules and compounds is easier after establishing a firm grasp of these simpler ones. There is a large variety of uses for these chemicals since this class of compounds is so vast. For example, a binary compound might be a binary covalent compound, a binary ionic compound, a binary acid, a binary transition metal compound, etc. Pharmacy,organic chemistry, analytical chemistry, industrial chemistry, materials chemistry, biotechnology, polymer chemistry, etc., are just some of the many scientific disciplines that study these compounds and their properties.

Frequently Asked Questions

1. Write the order of increasing acidity of hydrohalo acids.

The order of increasing acidity is:

HI>HBr>HCl>HFh

This happens because as the size of the anion increases, its nucleophilicity increases. I– is a strong nucleophile and prefers to stay in such a state. Thus its acidity is highest. 

2. Are all binary compounds conducting in nature?

No, only ionic compounds are conducting in nature. This is because of the formation of free flowing ions which conduct charge. Binary covalent compounds are  not conducting because their atoms are bonded. 

3. Is rust a binary compound?

The chemical formula for rust is FeO. Thus, it is an example of a binary compound since it is only made of two types of atoms. It is an ionic binary compound with iron in +2 oxidation state and it has an octahedral geometry. 

Introduction

Heat in an object does not remain stationary and tends to move from high-temperature to low-temperature areas. Thus, overheated materials tend to cool down while cold materials tend to absorb heat from the environment and warm up. Similarly, when two objects at different temperatures come into contact, heat energy is transferred from the hotter object to the cooler one. You might have seen dogs sticking out their tongues while panting. This helps them cool down because when they inhale, moisture in the air condenses on their tongues, forming liquid droplets that later evaporate. This evaporation requires thermal energy, which is supplied by their tongues, aiding them in cooling down.

Evaporation

Dogs cool themselves

What is conduction?

Conduction refers to the transfer of heat, electricity, or energy between particles of a substance without movement of the particles across regions of different temperatures themselves. It occurs in solids, liquids, and gases, and is the primary source of heat transfer inside solids. Since the atoms inside metals are placed close together, they conduct electricity well. Physically, conduction occurs by vibration. When a solid object is heated, its atoms/molecules start vibrating rapidly. However, since each atom or molecule is bonded to the next one, this vibration causes the neighbouring atoms to vibrate, and the process continues till the heat energy has spread across the whole solid.

Mode of conduction

Conduction occurs when there is a difference in temperatures across different portions of a material. Metals conduct heat very well whereas, liquids and solids tend to make bad conductors of heat. Furthermore, heat conduction is better when the surface area of the solid is large.

Thermal Conductivity

Thermal conductivity measures an object’s ability to transmit heat. It refers to the rate of heat transfer per unit time between the two ends of an object, given a specific cross-sectional area. We know that heat always flows from a higher temperature region to a lower temperature region. Suppose we were given a uniform shaft with length ‘l’ and cross-sectional area A. If the temperature at the two ends of the shaft were ,

, and Q amount of heat was transferred through the shaft, then it is natural that Q would be proportional to the temperature difference, the cross-sectional area, and the time taken for the conduction to occur. Further, it would be inversely proportional to the length of the shaft. Hence, we can say that

Here, K is the constant of proportionality known as the thermal conductivity.

What is convection?

Convection refers to the transfer of heat by the movement of particles in a medium from the hotter region to the colder region. It is a common way of heat transfer in liquids and gases. For instance, in a hot air balloon, the air molecules at the bottom of the balloon heat up and rise, creating low-density hot air that fills the balloon and causes it to ascend. Meanwhile, the cold air at the top of the balloon moves downward as the hot air rises, thus creating a continuous cycle of air movement.

Hot air balloons 

Mode of Convection

1. Chimneys are placed above stoves since hot molecules from our cooking will rise up and reach it via convection.
2. Land and sea breeze flow based on convection. The land gets warmer faster than the sea, causing air molecules above it to rise up. The cool air from the sea flows in to maintain a pressure balance. The reverse process occurs at night.

What is radiation

Radiation is the transfer of heat without the need for particles or a medium to carry it. For instance, thermal radiation is how the sun transfers heat to the earth. During the process of radiation, heat is emitted from hot objects in all directions and unlike conduction and convection, radiation can take place even in a vacuum since it doesn’t require any a medium. Radiation of heat occurs in the form of electromagnetic radiation. Hot objects emit radiation in all directions, which is responsible for carrying heat and allows the heat energy to reach different places without the need of a medium.

Examples of conduction, convection, and radiation

1. Metals are excellent conductors of heat, which makes them perfect for cooking. On the other hand, since wool is a bad conductor, we use it in our sweaters, which keeps the heat in.
2. Thermometers utilise mercury, which is also an excellent conductor.
3. Hot air balloons use the process of convection to function as described earlier.
4. We are advised to use bright colours in summers since they reflect the heat energy coming to us in the form of radiation. Similarly, aircrafts are made up of bright colours so that they reflect whatever heat energy is incident on them.

Summary

Heat can be transferred between objects of different temperatures through convection, conduction, and radiation. Conduction occurs in solids while convection occurs in liquids and gases. Radiation can occur without the need for a medium. An example of convection is that of sea breeze and land breeze. During the day, land surfaces become warmer than seawater, causing the hot air to rise and cooler air to move towards the land at night. Temperature can be measured using Fahrenheit, Celsius, and Kelvin scales. The amount of heat energy in an object depends on the material’s mass, the temperature difference, and the material’s properties.

 

Frequently Asked Questions

1. What is Widemann-Franz Law?

This law states that the thermal and electrical conductivities of metals are directly proportional to their temperature, and at a specific temperature, they are equal.

2. What is Black body radiation?

A black body is a material that absorbs all radiation incident upon it. When held at a constant temperature, it emits all of the absorbed energy. The emitted radiation is independent of the material’s properties and is called black body radiation and it is emitted uniformly in all directions.

3. What is Stefan-Boltzmann law?

This law states that the heat energy emitted from a perfectly black body is proportional to the fourth power of temperature.

4. What happens when an ice cube is placed in water?

The process of conduction takes place when an ice cube is immersed in water. Heat from the water flows into the ice cube and melts it.
5. Discuss cooling via evaporation

Evaporation is a process wherein a liquid substance absorbs heat and changes into a gaseous state. Since heat energy is required for this to occur, evaporation can take away excess heat from objects and cool them down.

Introduction

Reflection is a phenomenon wherein, when a wave hits a surface, it does not get absorbed. Instead, the incident energy is sent back from the surface. Metal surfaces can reflect as much as 80-90% of the light when highly polished and most commonly, mirrors are made using a silver coating that is deposited on the backside of the glass. The Hale Telescope located atop Mount Palomar in California is the world’s most reflective surface.

Similarly, refraction occurs when a wave crosses from one medium to another, which changes its direction and speed. One of the most commonly used optical devices is a lens, which is formed by the intersection of two spherical surfaces.

What is a lens?

A lens is one of the most commonly used optical devices made up of two intersecting spherical surfaces. The lens is said to be thin when the distances between the surfaces become small and it is not necessary for both of the surfaces to be spherical. In fact, one of them can be a plane as well. The line joining the centre of the two surfaces is known as the principal axis and the plane through this axis is known as the principal section of the lens. A point that lies on the principal section is known as the optical centre.

There are two types of lenses: Converging lenses, and diverging lenses.

Types of lens

Difference between Lens and Mirror

What is the concave lens? 

A concave lens is a type of lens that diverges a straight light beam, creating a virtual image that is smaller than the object itself. Both sides of the concave lens are curved inwards, giving it a concave shape. Due to this shape, these lenses are also known as diverging lenses as they cause light rays to spread out. For instance, when a ray coming from the sun falls on a concave lens parallel to the principal axis, it appears to emanate from a point on the principal axis known as the primary focal point of the lens.

Similarly, when a parallel ray is emitted from the opposite side of the lens, it will also appear to converge to the primary focal point, typically denoted by the letter ‘F’. Further, a light beam originating from the focal point will become parallel to the principal axis after passing through the lens.

Lens formula for concave lens

The lens formula is an equation applicable to all types of lenses and relates the distance of the object (u), the image distance (v), and the focal length of the lens. In the form given below, it is valid only for a thin lens but formulae for thick lenses have also been derived:

What is the convex lens?

A convex lens protrudes outwards on both sides and is thicker in the centre and thinner at the edges. It is called convex because it concentrates the light falling on it. When a light beam parallel to the primary axis falls on the lens, it passes through the primary focal point on the other side. Similarly, when a light beam originates from the primary focal point and hits the lens, it emerges parallel to the principal axis. 

One common example of the effects of this lens may be seen when it is held towards the sun and sunlight is focused on a piece of paper. The sharp, radiant image of the sun obtained this way is bright and has concentrated all the light rays in one point. This concentration is strong enough to burn the paper and the images formed this way are called real images.

Lens formula for convex lens

The lens formula for convex lenses is the same as that for concave lenses. That is,

Uses of convex and concave lens

Convex Lens

1. Convex lenses are used to manufacture magnifying glasses. 
2. Microscopes utilise convex lenses.
3. People suffering from hypermetropia are prescribed convex lenses, which can help focus the image correctly on the retina.
4. Convex lenses are also used in cameras.

Concave lens

1. Just like hypermetropia, myopia is corrected by using concave lenses.
2. Flashlights, binoculars, telescopes, eyeglasses, etc. are common devices that use concave lenses. 

Summary

A lens is a translucent medium formed by the intersection of two spherical surfaces or a spherical and a plane surface. When the surfaces are close, a thin lens is formed. There are two types of lenses: convex and concave. A convex lens protrudes outwards on both sides and is wide in the centre and narrow at the edges. A concave lens is bent inward on both sides and diverges the light rays that pass through it, earning it the name of diffuse lens. Ordinary mirrors are silver-coated on the back of glass. The Hale Telescope on Mount Palomar, California is the world’s largest reflector.

 

Frequently Asked Questions 

1. What is the law of light reflection?

There are two statements related to the law of reflection:

1. The incident ray, the reflected ray, and the surface normal will lie in one single plane.
2. The angle made by the incident and reflected rays with the vertical will be equal.

2. Define the power of a lens.

The power of a lens physically means its ability to bend light. Mathematically, it is measured as the inverse of the focal length of the lens.

 3. Calculate the power of a lens made of glass with a focal length of 150cm.

Given; Focal length 

Since the focal length and thus, the power is positive, this lens is concave.

4. What is Prism?

A prism is a solid object made of high quality glass, consisting of three non-parallel rectangular planes. One of these planes is the base, while the other two are polished and known as the refracting surfaces. The rough surface is called the base and the prism is made by joining all three surfaces to form a 3D triangle of sorts.

5. The focal length of the concave lens is 15cm. If an image is to be formed at 10 cm, how far should the object be placed from the lens?

We are given that

 v=-10 cm         f=-15 cm

Our job is to find u, which can be done via the lens formula

Thus, the image must be placed 30 cm to the left of the lens.

6. State Two Differences Between a Convex and a Concave Lens ?

1. Shape:

• Convex Lens: A convex lens is thicker in the middle and thinner at the edges. It has a shape that bulges outward, like the exterior of a sphere. It is also referred to as a converging lens because it focuses parallel light rays towards a single point.
• Concave Lens: A concave lens is thinner in the middle and thicker at the edges. Its shape curves inward, resembling the interior of a sphere. This type of lens is also called a diverging lens because it spreads parallel light rays away from each other.

2. Focal Point and Image Formation:

• Convex Lens: When parallel light rays pass through a convex lens, they converge or come together at a single point known as the focal point. Convex lenses can form both real and virtual images, depending on the object’s distance from the lens. Real images are formed when the object is placed beyond the focal length and are inverted, while virtual images are formed when the object is placed within the focal length and are upright.
• Concave Lens: When parallel light rays pass through a concave lens, they diverge or spread out. As a result, concave lenses only form virtual, upright, and reduced images. The focal point of a concave lens is the point from which the diverging rays appear to originate when extended backward.

Introduction

There are two types of mirrors – flat and curved. Flat mirrors are commonly used in homes while curved mirrors have specific applications in science and industry. Curved mirrors are classified into two types – concave and convex. The concave mirror has an inward curve and resembles a broken arc of a hollow sphere, while for the convex mirror, the reflecting surface is on the outside. Such special types of mirrors find widespread applications. For instance, when we need a wide-angle view, we can use convex mirrors and scientists can also use curved mirrors while designing telescopes and optical instruments.

Concave Mirror with Diagram and Formula

A concave mirror is curved inward on its inner reflecting surface and thus, you will see that it resembles the inside of a cave. The key parameters of concave mirrors are similar to those of a sphere, including the centre of curvature, the radius of curvature, the principal focus, and the focal length. To understand these terms better, take a look at the diagram below, which illustrates each of these parameters. We have shown the concave mirror detached from its parent sphere to aid in your understanding.

Concave mirror

Light rays coming from an object can reach the mirror one out of three ways:

1. It can pass through the focal point and hit the mirror. In such a case, reflection makes it parallel to the principal axis.
2. A light ray that crosses the centre of curvature before hitting the mirror will retrace the path it took initially.
3. Light rays can also hit the mirror while travelling parallel to the principal axis. Such rays will cross the focal point of the lens after reflection.
4. Finally, if a ray doesn’t satisfy either of the above two criteria, it will reflect from the mirror following the law of reflection, i.e., the angle of incidence will be the same as the angle of reflection.

Except for when the object is placed between the focal point and the pole of the mirror, concave mirrors produce a real and inverted image. Two possible ways of creating an image using this mirror are shown below:

Concave mirror

Concave mirror

One common example of the use of this mirror is in flashlights and torches, which use a concave mirror around the bulb, making the output beam parallel to the principal axis.

Example: For an object placed 90 cm from a concave mirror of focal length 30 cm. What is the distance at which the image will be formed?

It is a common norm to use u and v to represent the image and object distances, respectively. If f is the focal length of the mirror, then the mirror formula reads:

While performing measurements, certain sign conventions are followed. These are stated in the diagram below:

Hence, we have:

 

Thus, the image will be formed 45 cm towards the left side of the mirror.

Convex Mirror with Diagram and Formula

A convex mirror has a reflecting surface that is curved outward and is characterised by the same parameters as its concave counterpart. Thus, concepts like the centre of curvature, pole, radius of curvature, focus, etc. are present here as well and defined similarly. The mirror formula remains the same but the object distance is taken as positive since convex mirrors tend to form a virtual image towards the right side of the mirror. We can trace the light rays for a convex mirror just like a concave mirror.

Convex mirror ray tracing

The following properties may be noted for a convex mirror:

• A ray incident parallel to the principal axis will seem to emanate from the focal point.
• Light rays that fall on the pole of the mirror at an angle will be reflected on the other side of the principal axis at the same angle.
• A ray that seems to hit the centre of curvature of the mirror will not be deflected.
  

Characteristics Of Concave and Convex Mirror

Concave mirror

The images formed via a concave mirror can be seen in the diagram below, which illustrates the characteristics of this mirror. Objects placed in front of the mirror are represented in red while the images formed are represented in blue.

We can draw the following inferences:

• When the object is placed beyond the focal point of the mirror, a virtual image is formed behind the mirror.
• For an object placed at the focal point, no image is formed.
• For an object placed at the centre of curvature, an inverted image is formed at the centre of curvature itself.

Concave mirror

Description: Different image characteristics for a concave mirror.

Convex mirror

Just as in the case of a concave mirror, we can perform similar analysis for a convex mirror as well. Ray Tracing allows us to determine how different objects will appear. Generally, a convex mirror forms virtual images.

Convex mirror

For a convex mirror, the images formed are virtual and thus impossible to project on a screen. 

Convex mirror

Uses Of Concave and Convex Mirror

Uses of Concave Mirrors:

1. Vehicle Headlights: Concave mirrors are used in vehicle headlights to direct the light from the bulb into a parallel beam, improving visibility on the road.
2. Shaving and Makeup Mirrors: Concave mirrors provide a magnified and upright image when the object is placed within the focal length, making them ideal for close-up tasks like shaving or applying makeup.
3. Ophthalmoscopes: Ophthalmologists use concave mirrors in ophthalmoscopes to examine the interior of a patient’s eye, including the retina and optic nerve.
4. ENT Examination: Concave mirrors are used by ENT doctors to focus light into the patient’s ear, nose, or throat, making it easier to examine these areas.
5. Solar Concentrators: Concave mirrors are used in solar concentrators to focus sunlight onto a small area, such as a solar cell or a heat-absorbing target, maximizing the energy collected.

Uses of Convex Mirrors:

1. Rear-View Mirrors in Vehicles: Convex mirrors are used as rear-view mirrors in automobiles because they provide a wider field of view, allowing drivers to see more of the area behind the vehicle. However, objects appear smaller and farther away in a convex mirror, so caution must be exercised while judging distances.
2. Security Mirrors: Convex mirrors are used in ATMs, retail stores, and other locations for security purposes. Their wide field of view allows surveillance of large areas with a single mirror, making it easier to monitor activity and spot potential security issues.

Difference Between Concave and Convex Mirror

Summary

With only slight differences in construction, concave and convex mirrors lead to vastly different images, which makes them quite interesting and useful in several applications. In this article, we discussed the various factors which were common across these two types of mirrors and showcased the diagrams, formulae, and uses of both. Further, we tabulated the differences in their properties and characteristics.

 

Frequently Asked Questions

1. What is magnification?

Magnification measures the increase or decrease in size of the image as compared to the size of the object. It is defined as the ratio of height of image to height of object.

2.  What is the focal plane?

The focal plane is defined as that plane which lies perpendicular to the principal axis and passes through the focal point of the lens.

3. What is aperture?

The aperture measures the size of the mirror, and it is the diameter of the mirror itself.

4. What happens when an object is taken farther away from a concave mirror?

For a concave mirror, the image size becomes smaller and smaller as the object is pulled farther and farther from the mirror.

5. What does the value of magnification indicate?

The sign of magnification can tell us whether the image is erect or inverted. Further, its magnitude is greater than 1 if the image is magnified or less than 1 if diminished.

What Are Aldehydes?

Carbon (C) and oxygen (O) form a double bond in aldehyde, making it a carbonyl functional group; carbon (H) and an alkyl group (C=O) form a single bond. As a rule of thumb, aldehyde is denoted as R-CHO. The letter “R” stands for the alkyl group. Carbon (C) is double-bonded to oxygen (O) in all aldehyde chemical compounds, forming the carbonyl group. The prefix “al” is appended to the name of any chemical compound that contains an aldehyde group

What Are Ketones?

A ketone also contains a carbonyl group and is thus a functional group. Here, two alkyl groups (R) are connected by a single bond while the carbonyl carbon (C) is double-bonded to oxygen (O). Ketones are typically written as R-CO-R, where R is an alkyl group. The prefix “one” is added to the name of any compound that contains a ketone group. 

Properties of Ketones 

To put it simply, ketones are liquids at room temperature. Use acetone as an illustration. Ketones have a higher boiling point than aldehydes and alcohols because the carbonyl group they contain exhibits dipolar attraction. The compound’s boiling point rises proportionally with its magnitude. In general, ketones of a lower molecular weight dissolve well in water, but this solubility declines with increasing ketone molecular size.

Properties of Aldehydes

Aldehydes come in a wide range of physical forms. Formaldehyde is one such chemical that, at room temperature, exists in the gaseous state. Formalin is the name given to an aqueous solution of the substance. Most other common aldehydes are liquids at room temperature, however others, depending on the number of alkyl groups, are solids. The lower aldehydes have a strong odour, whereas the higher aldehydes are pleasant, which is why they are used in fragrances. 

Due to the dipolar attraction seen in the polar carbonyl group present in aldehyde, the boiling point of aldehyde is generally high. 

Aldehyde show dissolution in water and other solvents. This is because they have lone pair of electrons in the oxygen (O) of the carbonyl group (C=O) which forms an H- bond with the hydrogen of water. The aldehydes which contain four carbon atoms are generally soluble in water but the solubility of aldehyde in water decreases as the size of the alkyl group increases.

Occurrence Of Ketones And Aldehydes

Many different types of microbes and plants are natural sources of ketones and aldehydes. Examples include cinnamaldehyde from cinnamon bark, citral from lemongrass, vanillin from vanilla bean, carvone from spearmint and caraway, camphor from the camphor tree, and helminthosporal from poisonous fungi, to name a few. Ketones can also be found in animals, such as the muscone found in musk deer, the sex hormones testosterone in males and progesterone in females, and the adrenal hormone cortisone.

Preparation Of Ketones And Aldehydes

Preparation of Aldehyde

Oxidation of primary alcohols: Primary alcohols can be treated with Pyridinium chlorochromate in dichloromethane to form aldehydes.

Dehydrogenation of primary alcohols : Dehydrogenation means the removal of the hydrogen molecule. Primary alcohol undergoes dehydrogenation in the availability of copper forms aldehyde.

From acid chlorides

The reduction of the acid chloride with hydrogen in the availability of palladium catalyst present over barium sulphate with a small quantity of quinoline gives aldehyde. The reaction is said to be Rosenmund’s reaction. 

Preparation from carboxylic acid

When the vapours of carboxylic acid are passed over manganese oxide at 573 K, the aldehyde is produced.  A common example is passing formic through manganese oxide at 573 K to give formaldehyde, carbon dioxide and water.

Preparation from alkenes

Alkenes reacting with ozone in presence of carbon tetrachloride give ozonides which further break down into two molecules of aldehyde in presence of zinc dust and water.

Preparation of ketones

From acid chloride: On reacting with dialkyl cadmium, ketone compound are formed from acid chloride.

Here, acetyl chloride reacting with dimethyl cadmium forms acetone.

From carboxylic acid: When vapours of acetic acid is passed through manganous oxide, acetone is produced.

From alkenes:
2, 3-Dimethylbut-2-ene on ozonolysis gives acetone.

Here, 2, 3-Dimethylbut-2-ene reacting with ozone in presence of carbon tetrachloride gives ozonide which breaks down to acetone.

From akynes:

Propyne reacting with a hydrated mixture of dilute sulphuric acid and mercuric sulphate gives acetaldehyde.

Uses Of Aldehydes And Ketones

Perfumes typically include organic compounds containing aldehyde, such as vanilla, orange rind, rose, and citronella. Because of their pleasant aroma, these chemicals are synthesised in laboratories and used in the creation of perfumes and colognes. Because of its signature scent, benzaldehyde is also a popular ingredient in fragrances.

Aldehydes have several industrial applications, including in the production of chemical compounds, dyes, and resins. Because of its effectiveness as a preservative for biological specimens and its antimicrobial qualities, formaldehyde is often manufactured industrially on a larger scale. The most widely utilised ketone molecule, acetone is primarily employed as a solvent in the production of chemicals like iodoform and iodoform. The nail polish remover contains it.

Formation by Oxidation of Alcohols

Aldehyde: Primary alcohol oxidises of aldehyde in presence of acidified potassium dichromate (\({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\)) or alkaline potassium permanganate (\({\bf{KMn}}{{\bf{o}}_4}\)).

Here, ethyl alcohol oxidises to acetaldehyde.

Ketone: Secondary alcohol on oxidation in presence of acidified potassium dichromate (\({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\)) or alkaline potassium permanganate (\({\bf{KMn}}{{\bf{o}}_4}\)) gives ketone.

Here, isopropyl alcohol is oxidised to acetone.

Formation by Alcohols Dehydrogenation

Aldehyde: Primary alcohol undergoes dehydrogenation in the availability of copper forms aldehyde.

Ethyl alcohol on heating with copper changes to acetaldehyde and hydrogen molecule is removed.

Ketone: Heating of secondary alcohol in presence of reduced Cu at 573 K forms ketone.

Summary

Carbonyl-containing organic substances include aldehydes and ketones. Aldehyde and ketones can be synthesised industrially on a massive scale in addition to being derived naturally from plants and bacteria. Its versatility in application has led to their widespread use. Both chloroform and iodoform require acetone as an input in their production. Dye manufacturing (like malachite green) and chemical synthesis (such benzoic acid and benzoyl chloride) all rely on benzaldehyde. There are a variety of additional organic molecules that can be used as building blocks for making aldehyde and ketones, respectively.

Frequently Asked Questions

1. Which test is common for the detection of both aldehyde and ketone groups?

Ans: Both aldehyde and ketone groups give 2, 4-Dinitrophenylhydrazine. When 2,4-DNP or Brady’s reagent is reacted with pure carbonyls, it forms precipitate which is yellow-orange in colour. 

2. What is a Schiff Base?

Ans: A Schiff base is a compound with the general structure R2C=NR’ and is considered as a subclass of imines. Schiff’s test is a chemical test used to check for the presence of aldehydes in a given analyte. 

3. Out of aldehydes and ketones which one is more reactive and why?

Ans: Aldehydes are more reactive towards nucleophilic addition reactions. Since the carbonyl group of ketones is connected to alkyl groups, and the alkyl group has electron donating inductive effect, it increases electron density on carbon of carbonyl group in ketones, making it less electrophilic.

What are Aldehydes?

Carbon in an aldehyde forms double bonds to oxygen and single bonds to hydrogen and an alkyl group, making it a carbonyl functional group.  The letter “R” stands for the alkyl group. Known as the carbonyl group, aldehyde chemical compounds all have a carbon atom double-bonded to oxygen. An aldehyde group’s carbon atom can come from any unsaturated, saturated, or cyclic carbon chain. A carbon atom in an aldehydic molecule will have at least one hydrogen atom attached to it.

Naturally Occurring Aldehydes

Naturally occurring aldehyde compounds are widespread in flora and fauna. Vanillin can be found in vanilla beans and cinnamaldehyde in cinnamon bark. Citral is extracted from lemongrass. 

General Properties Of Aldehydes

Physical State: Aldehydes come in a wide range of physical forms. Formaldehyde is one such chemical that, at room temperature, exists in the gaseous state. Formalin is the name given to an aqueous solution of the substance. Most other common aldehydes are liquids at room temperature, however others, depending on the number of alkyl groups, are solids. The lower aldehydes have a strong odour, whereas the higher aldehydes are pleasant, which is why they are used in fragrances.

Boiling Points:  Due to the dipolar attraction seen in the polar carbonyl group present in aldehyde, the boiling point of aldehyde is generally high. 

Solubility:  Water and other solvents are effective at dissolving aldehyde. The oxygen (O) in the C=O molecule has a lone pair of electrons, so it can form a H bond with the hydrogen in water. In general, aldehydes with four carbon atoms are soluble in water, although the solubility diminishes with increasing alkyl group size.

Uses Of Aldehydes

• Organic compounds like vanilla, orange rind, rose and citronella contain aldehyde. These compounds are created synthetically in laboratories and utilised for the production of perfumes and colognes due to their sweet smell.
• Aldehydes are used for making different organic compounds, dyes, and resins. Formaldehyde is prepared industrially on a larger scale and is used as a preservative for biological specimens and also has antibacterial properties.

Preparation of Aldehydes

There are many preparative methods for aldehydes. A few of them are discussed below.

Oxidation of primary alcohols: Primary alcohols can be treated with Pyridinium chlorochromate in dichloromethane to form aldehydes.

Dehydrogenation of primary alcohols : Dehydrogenation means the removal of the hydrogen molecule. Primary alcohol undergoes dehydrogenation in the availability of copper forms aldehyde.

From acid chlorides

The reduction of the acid chloride with hydrogen in the availability of palladium catalyst present over barium sulphate with a small quantity of quinoline gives aldehyde. The reaction is said as Rosenmund’s reaction. 

Preparation from carboxylic acid

When the vapours of carboxylic acid are passed over manganese oxide at 573 K, the aldehyde is produced.  A common example is passing formic through manganese oxide at 573 K to give formaldehyde, carbon dioxide and water.

Preparation from alkenes

Alkenes reacting with ozone in presence of carbon tetrachloride give ozonides which further break down into two molecules of aldehyde in presence of zinc dust and water.

Nomenclature of Aldehydes

Aldehydes can be identified with the suffix -al, in other words, any hydrocarbon name that ends with the suffix -al is referred to as aldehyde. For example methanal, ethanal, and propanal. The nomenclature of aldehyde is done using the IUPAC naming system. IUPAC stands for International union of pure and applied chemistry. 

1. First, the numbering of carbon atoms starts from the carbonyl carbon. Here, the number of total carbon (C) atoms is three so the hydrocarbon chain is “propane” and the root word is “propan”.
2. As the aldehyde group is present (-CHO) the “ane” suffix is changed by “al” forming propanal.
3. So, the IUPAC name of the given compound is propanal.

Structure of Aldehydes

The general structure of aldehyde is shown below.

 Aldehyde

Here, the carbonyl carbon is \(s{p^{2}}\) hybridised. The chemical compounds containing carbonyl groups like aldehyde and ketone have planar geometry. The bond angle is 120 degrees. In the carbonyl group, the oxygen atom is more electronegative in nature than carbon which indicates that it is a polar group. As a result, the dipole moment is 2.3 D to 2.8 D.

Tests for Aldehydes

2, 4-DNP Test: Here, the organic compound is mixed with an acidic solution of 2, 4-dinitrophenylhydrazine along with methanol. After some time, a formation of a red precipitate is observed. The red precipitate is of 2,4-dinitrophenylhydrazone. The solid crystals are filtered and by recrystallisation method, solid mass is obtained. The hydrazone derivative has a distinct melting and boiling point which helps to detect the carbonyl group. Further, as the presence of the carbonyl group is detected, we can also find out whether the compound is ketone or aldehyde.

As the precipitate obtained is in solid form, it can be filtered out and the melting point of the solid can be determined. By comparing the melting point of the precipitate to the known value of ketone and aldehyde, the carbonyl group present in the compound can be detected.

Schiff’s reagent: It is a pink colour dye which gets decolourised by passing sulphur dioxide gas. When aldehyde is treated with Schiff’s reagent, the colour is retained.

Summary

Aldehyde is one of the classes of functional groups containing a carbonyl carbon attached to oxygen by a double bond and to an alkyl group and hydrogen by a single bond. The aldehyde can be identified by the suffix “al”. The general formula of aldehyde is R-CHO. Higher grade aldehydes are used for the preparation of perfumes and colouring agents due to their sweet smell. The aldehyde can also be synthesised by different methods as discussed. A few examples of aldehydes are formaldehyde, Ethanal, Propanal, Butanal etc. Some naturally occurring aldehydes are vanillin, citral, etc.

Frequently Asked Questions

1. Why are aromatic aldehydes less reactive than aliphatic aldehydes?

Ans: Aromatic aldehydes are less reactive because the lone pair of oxygen atoms is involved in resonance with the benzene molecule. This makes the carbonyl group less nucleophilic. 

2. Which reducing agent is used for aldehydes?

Ans: Sodium Borohydride is also called as tetra hydrido borate is used as a reducing agent of aldehydes. The aldehydes are converted into primary alcohols. 

3. Which type of aldehyde compound can undergo aldol condensation?

Ans: The aldehyde compound containing alpha hydrogen undergo aldol condensation. This is because only compounds with alpha hydrogen can form beta-hydroxy aldehydes, which is the end product of the reaction. 

Introduction

The -OH bond is present in the functional group of alcohols and phenols. Carbonyl compounds are another type of organic chemical that contain the C=O group. More than one class of chemical compounds has this cluster. Carbonyl compounds, which include aldehydes and ketones, are a class of organic molecules distinguished by the presence of a carbonyl group (>C=O). The group is attached to a Hydrogen atom in aldehydes. Lack of hydrogen allows the carbonyl group to be referred to as the ketonic group; this group is absent in ketones.

Whereas aromatic ketones have no alkyl groups, aliphatic ketones have from one to three. An aryl group must be present in at least one of them. Both families share a carbonyl group, which explains why their members are so similar in appearance and how they are prepared. Nevertheless, aldehydes and ketones have different reactivities because of the presence of a hydrogen atom in aldehydes against the absence of such an atom in ketones. Aldehydes and ketones are similar in that they are both highly reactive. Because of the carbonyl group’s reactivity as a polar, Pi ()-bonded carbonyl radical.

What are Alcohols?

For alcohols and phenols to develop, one or more hydrogen atoms must be exchanged from the original hydrocarbon. In regards to alcohols, the -OH is the hydroxyl group. A phenolic group resides in or is conjugated to a benzene ring. The alcohols do not allow for any search resonance. That’s why phenols are so acidic, whereas alcohols are so basic. Monohydric alcohols, or -OH alcohols, only have one hydroxyl (-OH) group.

In chemical notation, these are written as R-OH. Based on the characteristics of the carbon atoms with which the -OH group forms a bond, these are further classified as primary (1°), secondary (2°), or tertiary (3°) hydroxyl groups.

Oxidation of Alcohols to Aldehydes and Ketones

Method of Preparation of Aldehydes 

Aldehydes are the oxidation products of primary alcohols. The oxidation is normally carried with acidified \({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\) or aqueous/alkaline \({\bf{KMn}}{{\bf{o}}_4}\).

When Ethyl alcohol is reacted with alkaline \({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\) it immediately oxidised to Acetaldehyde and gives water.

\({\bf{C}}{{\bf{H}}_3}{\bf{C}}{{\bf{H}}_2}{\bf{OH}} + {\rm{ }}{\bf{KMn}}{{\bf{O}}_4} \to {\bf{C}}{{\bf{H}}_3}{\bf{CHO}}{\rm{ }} + {{\bf{H}}_2}{\bf{O}}\)

In case alcohols, particularly aromatic, have poor solubility in water, then a solution of chromic acid (\({{\bf{H}}_2}{\bf{Cr}}{{\bf{O}}_4}\))  dissolved in acetone (\({{\bf{C}}_3}{{\bf{H}}_6}{\bf{O}}\)) can be used. This is known as Jones reagent.

\({{\bf{C}}_6}{{\bf{H}}_5} – {\bf{C}}{{\bf{H}}_2}{\bf{OH}}{\rm{ }} + {{\bf{H}}_2}{\bf{Cr}}{{\bf{O}}_4} + {{\bf{C}}_3}{{\bf{H}}_6}{\bf{O}} \to {{\bf{C}}_6}{{\bf{H}}_5} – {\bf{CHO}}{\rm{ }} + {\rm{ }}{\bf{Water}}\)

Method of Preparation of Ketones

Ketones are products of oxidation of secondary alcohols. The oxidation is normally carried with acidified \({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\) or aqueous/alkaline \(\;{\bf{KMn}}{{\bf{o}}_4}\).

\({{\bf{C}}_2}{{\bf{H}}_6}{\bf{CHOH}} + {\rm{ }}{\bf{KMn}}{{\bf{O}}_4} \to {{\bf{C}}_2}{{\bf{H}}_6}{\bf{C}} = {\bf{O}}{\rm{ }} + {{\bf{H}}_2}{\bf{O}}\)

Oxidation of secondary alcohols can also be done with the help of oppenaur oxidation in which the secretarial course is refluxed with excess acetone in the presence of aluminium tertiary butoxide in benzene or toluene solution. The secondary alcohol is oxidised to corresponding ketone while ketones simultaneously reduce to secondary alcohol.

Reduction of Alcohols

• Alkyl halides are best prepared from alcohols by replacing the group with halogen atom ().
• Alkyl chlorides or chloroalkanes are prepared by reacting in alcohol with a mixture of anhydrous and Hydrogen Chloride gas (mixture is called Lucas reagent). This is known as Groove’s process.

\({\bf{C}}{{\bf{H}}_3}{\bf{C}}{{\bf{H}}_2}{\bf{OH}}{\rm{ }} + {\rm{ }}{\bf{HCl}}\left( {\bf{g}} \right){\rm{ }} + {\rm{ }}{\bf{Anhy}}{\rm{ }}{\bf{ZnC}}{{\bf{l}}_2} \to {\bf{C}}{{\bf{H}}_3}{\bf{C}}{{\bf{H}}_2}{\bf{Cl}}{\rm{ }} + {{\bf{H}}_2}{\bf{O}}\)

Identification Tests of Alcohols

Special tests are employed to detect alcohols and to determine their specific nature. These are described as follows.

Vector Meyer’s Test (Red blue Colourless Test)

The given alcohols are first converted to the alkyl iodide by reacting \(p/{I_2}\left( {p{I_3}} \right)\)The alkyl iodide is converted to the corresponding Nitro derivative with silver nitrite (\(AgN{O_2}\)). The Nitro derivative is then reacted with nitrous acid(\(NaN{O_2} + HCl\)) and the resulting solution is made alkaline.

• A blood red colouration indicates primary alcohol.
• A blue colouration indicates secondary alcohol
• A colourless solution represents tertiary alcohol

Lucas Reagent Test

This test is based on the reactivities of primary secondary and tertiary alcohols with Hydrochloric acid. The given alcohols are treated with Lucas reagent, which is an equal mixture of concentrated  and anhydrous \(ZnC{l_2}\) which is a dehydrating agent. The product is alkyl chloride or chloroalkane followed by white, turbidity or cloudiness.

\({\bf{Primary}},{\rm{ }}{\bf{Secondary}},{\rm{ }}{\bf{Tertiary}}{\rm{ }}{\bf{Alcohol}}{\rm{ }} + {\rm{ }}{\bf{HCl}}{\rm{ }} + {\rm{ }}{\bf{Anhy}}{\rm{ }}{\bf{ZnC}}{{\bf{l}}_2} \to {\bf{Alkyl}}{\rm{ }}{\bf{Chloride}}{\rm{ }} + {{\bf{H}}_2}{\bf{O}}\)

The time taken for the appearance of turbidity is different in the 3 types of alcohols and affords a method for their distinction.

1. If the turbidity appears immediately, alcohol is tertiary
2. If the turbidity appears after sometime, alcohol is secondary
3. In case the turbidity appears on heating, alcohol is primary

Summary

The alcohol and phenol functional groups both feature a -oH bond. Carbonyl compounds are another type of organic chemical that contain the >C=O group. More than one class of chemical compounds has this cluster. Carbonyl compounds, which include aldehydes and ketones, are a class of organic molecules distinguished by the presence of a carbonyl group (>C=O). The group is attached to a Hydrogen atom in aldehydes. There is no hydrogen atom in ketones, and the carbonyl group is sometimes referred to as the ketonic group.

 

Frequently Asked Questions

1. What are the environmental impacts of the oxidation of alcohols?

Ans: Oxidation of alcohols makes heavy use of water resources. It needs resources like land and water in order to flourish. It occurs in high energy consumption factories. Creates waste that ends up in landfills because of packaging.

2. What is the role of a catalyst in the oxidation of alcohols?

Ans: Catalytic oxidation of alcohols is an essential process for energy conversion, production of fine chemicals and pharmaceutical intermediates. It makes the process quick and increases yield.

3. Why we are unable to get aldehyde on reaction between primary alcohols and \({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\) ?

Ans: \({{\bf{K}}_2}{\bf{C}}{{\bf{r}}_2}{{\bf{O}}_7}\)  cannot be used to oxidize primary alcohols to aldehydes. The oxidation will not stop at aldehyde stage. It will further continue to carboxylic acid.