Category: Chemistry

Introduction

Circuit boards, plastic light fixtures, switches, and sockets can all be made of the synthetic material known as Bakelite. The characteristics include non-absorbency and non-conductivity, as well as high-temperature resistance. Because it is utilized in electronic devices, it is referred to as “Bakelite.” A heated mixture of granular phenolic resin, sawdust, and asbestos is used to make Bakelite, which is then poured into a mould. The phenolic resin was the first artificial resin. Plastic materials come in a wide variety. 

Types of plastics

They can be divided into two classes: Thermoplastics and Thermosetting.

Thermoplastics: These are the plastic materials used to make the handles of toothbrushes and bags. Thermoplastics are heated to convert into their different forms.

Thermosetting: After heating, the hardness of this plastic increases. Bakelite is one type of thermosetting plastic.

Bakelite preparation

Bakelite is prepared by following such steps.

1. 25 ml glacial acetic acid is taken in a beaker. 12.5 ml 40% formaldehyde solution is mixed with it and heated.
2. After some time, 10-gram phenol is added to it and at the end 12-15 ml of HCl solution is mixed.
3. It is put in a water bath and heated gently until a solid mass appears.
4. Then it is passed through the funnel, fitted with filter paper, and Bakelite remains as a solid compound.

Structure of Bakelite:

In the Bakelite structure, there is a cross-linking between phenol and formaldehyde. Bakelite can be written chemically as\(\;{({C_6}{H_6}O – C{H_2}OH)_n}\).

Properties of Bakelite

1. Bakelite can be easily generated, and the mouldings of Bakelite are corrosion and thermal-resistant.
2. It would be resistive to current flow because of its low conductivity to electricity.
3. Due to its low electrical properties and high heat resistance, Bakelite has also been used primarily in the production of mechanical and electrical components for electrical devices.
4. Bakelite contains phenolic components in the structure. For this, it is widely used in bindings.
5. Bakelite is moulded at a very rapid rate. 
6. Bakelite enables the production of extremely smooth mould.
7. Bakelite can endure harmful solvents.
8. When heated, it melts and solidifies. Then It becomes hard and can be moulded into desired shapes.
9. The cost of moulding decreases when an inert filler is used.

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Uses of Bakelite

1. To offer adequate security, it is used in parts that do not use radios or other electronic parts, such as plugs, buttons, hoods, wire cables, brakes, and so on and due to its shaping capacity, it is frequently used in everyday culture.
2. Due to its strong tensile strength and thermosetting nature, Bakelite may maintain its shape even after extensive production.
3. It has the ability to mould itself in various shapes, making this substance too much useful in modern society.
4. It is extensively used in making the parts of washing machines, cooking utensils, watches, toys, and many more.

Importance of Bakelite

1. Due to its many important uses as the first synthetic polymer, Bakelite has been appropriately termed “a thousand-use material.” Bakelite is used in the production of many products, including handles of plastic, telephones, ATMs, and so on.
2. Due to its strong resistance to both heat and electricity, it is used to produce numerous electronic components, sensors, and vehicle parts.
3. Besides these, the features of Bakelite are improved in various ways for better uses.

     For these reasons, Bakelite is so important in our daily life.

Summary

Being one of the most widely utilized thermoplastic materials in the nation, it is used to produce many other polymers. It’s vital to remember that because of the distinct characteristics of such a polymer, changing the temperature has little impact on the physical and chemical characteristics of that kind of substance. Having phenolic components in its structure, it is widely used in bindings. But it is very dangerous for human health.

Frequently Asked Questions

1. What occurs when Bakelite is heated?

Ans: As a result of heating a Bakelite, a watery condensation compound (Known as Bakelite A) is produced. Bakelite A becomes dissolved in acetone, alcohol, or extra phenol. Additional heating makes the product somewhat soluble, though the heat can still soften it. The consequence of prolonged heating is the formation of “insoluble, hard gum.”

2. Is Bakelite able to resist fire?

Ans: The handles of many kitchen appliances (fry pans, pressure cookers) are made of sturdy and long-lasting plastic known as Bakelite. It is also a bad conductor of electricity and heat, just like Melamine.

3. Is Bakelite resistant to chemicals?

Bakelite is a tough and chemically inert plastic that was created by combining phenol and formaldehyde. These two substances were obtained from coal tar and wood alcohol (methanol) respectively. Bakelite is inert to chemicals.

Introduction 

The scientist, Antonio Lavoisier, introduced the law of conservation of mass in the year 1789. According to him, mass can’t be destroyed or generated. But mass can be transformed from one form to another. In our daily life, we also utilize this law. For example, in the burning process of wood, the total masses of the products (gases, ashes, soot) and the masses of the reactants (charcoal and oxygen)remain the same. 

Define “The Law of Conservation Of Mass”:

This law states: “matter cannot be created or destroyed in a chemical reaction”. That means the total masses of reactants or products should be the same after a reaction.

Application of the law of conservation of mass in different reactions:

1. During phase transition: During the transformation of any substance from its solid to liquid and then to vapour, the total mass of the substance remains constant. In the physical change of ice to water and then water to vapour, the mass of water in its three states remains the same.

Ice ⇌ water ⇌ vapour

2. During chemical reaction: Total masses of the reactants and the products remain the same after a successful chemical reaction. Like, in the combustion reaction of methane, carbon dioxide \(C{O_2}\) and water \({H_2}O\) are produced. The total masses of reactants (\(C{H_4}\)and \({O_2}\)) remain the same as the masses of products (\(C{O_2}\) and \({H_2}O\)).

\[C{H_4} + 2{O_2} \to C{O_2} + 2{H_2}O\]

3. During rearrangement reaction: Calcium carbonate produces calcium oxide and carbon dioxide on heating. The masses of reactants (calcium carbonate) and the products (calcium oxide and carbon dioxide)remain the same.

\[CaC{O_3} \to {\rm{ }}CaO{\rm{ }} + {\rm{ }}C{O_2}\]

Methods to examine the law of conservation of mass:

1. In the reaction of Barium chloride and magnesium sulfate: The law of conservation of mass can be proved by the following reaction. For this, some steps need to be followed.

• First, a particular amount of Barium chloride (\(BaC{l_2}.2{H_2}O\)) is weighed. Then some amount of distilled water is mixed with it. And this mixture is named A.
• Then some definite amount of magnesium sulfate (\(MgS{O_4}\)) is mixed with the same amount of water as A. This mixture is indicated as B.
• Then another empty beaker(C) is taken and weighed. The whole solution of A and B is poured into beaker C.
• A white precipitate of \(BaS{O_4}\) is formed in beaker C. Then the weight of beaker C is taken again.
• Now the weight of empty beaker C is subtracted from the beaker C, containing products.
• Comparing the masses of A, B, and C, we get that the total masses of the solutions A and B match with the product formed in beaker C.

In this way, the conservation of mass can be proved.

\[BaC{l_2} + {\rm{ }}MgS{O_4} \to {\rm{ }}BaS{O_4} + {\rm{ }}MgC{l_2}\]

2. In the reaction of silver nitrate and sodium chloride: This law can be proved by the following reaction of silver nitrate and sodium chloride. For this, the following steps need to be followed.

• Silver nitrate and sodium chloride solutions are made separately. Sodium chloride solution is taken in a conical flask and silver nitrate is taken in an ignition tube.
• Then the ignition tube is suspended into the flask and the flask is fitted with a cork.
• Now the mass of the conical flask is recorded, and then the conical flask is tilted for the reaction of silver nitrate and sodium chloride.
• Now, the product \(AgCl\) is precipitated as a solid. At this stage, the mass of the conical flask is recorded again.
• It is found that the masses of reactants and products are the same.

\[NaCl{\rm{ }} + {\rm{ }}AgN{O_3} \to {\rm{ }}AgCl{\rm{ }} + {\rm{ }}NaN{O_3}\]

Summary

The law of conservation of mass tells us that the mass of reactants and products is always the same after a reaction. That is, the total mass is always conserved in different types of chemical reactions as well as in physical changes. This law can be proved by some reactions in the laboratory. This law is very essential as the unknown mass of any reactant or product can be determined. From this law, any chemical reaction can be balanced easily.

Frequently Asked Questions

1. What are the drawbacks of the law of conservation of mass?

Ans: This law is valid for only chemical reactions and physical changes. But does not apply to nuclear reactions. During a nuclear reaction, heat is produced. That means some mass is converted to heat. So the mass is not conserved in the nuclear reaction.

2. Is there any difference between the conservation of mass and the conservation of energy?

Ans: Conservation of mass and energy were commonly considered to be separate concepts. However, special relativity demonstrates that mass and energy are linked by the formula \(E{\rm{ }} = {\rm{ }}m{c^2}\), and science currently holds the belief that the sum of mass and energy is conserved.

3. Which equation corresponds with the principle of mass conservation?

Ans: The law of mass conservation can be expressed by a balanced chemical equation. In a balanced chemical equation, the number of each element involved in a reaction is always the same on the reactants and products side.

Introduction

Chemical reactions operate on the type of reaction and change principle, which states that when a reactive substance interacts with other chemicals, different reactions will occur. Chemical reactions occur in stable or least reactive compounds as well, albeit under more extreme conditions. When reactants combine to produce a product, heat is released or absorbed, bubbles, gas, and fumes are formed, and the colours of the reactants change, resulting in a chemical change. During a  physical change, there is an interconversion of conditions. There are various types of chemical reactions, such as combination, decomposition, and displacement reactions, and certain changes occur during these reactions.

What is a Combustion Reaction

A combustion reaction is an exothermic chemical reaction that occurs between a fuel (or reductant) and an oxidant and results in the formation of oxidised products. This process occurs at high temperatures. This is a redox reaction because it involves the simultaneous reduction and oxidation of substances. A struck match, for example, generates friction, which raises the temperature (or energy) of the head (more than activation energy), at which the chemicals react and generate more energy in the form of heat, which tends to escape into the atmosphere. A moist matchstick head or the presence of blowing wind prevents the temperature from rising. As a result, the matchstick’s head does not burn. Another common example of combustion is the combustion of fuel in automobiles, which produces smoke.

Examples of Combustion Reaction

Methane combustion

Methane is a natural gas that burns the cleanest of all fossil fuels. The term “cleanest” refers to the absence of harmful toxins. It completely degrades into water and carbon dioxide.

Butane combustion

Lighters use the combustion process to break down butane. Butane is significantly less expensive than other fossil fuels. This is also a clean fuel, but it emits a lot of carbon dioxide into the atmosphere.

Butanol combustion

Butanol combustion occurs during the transportation process. Butanol has a high energy density and a low vapour pressure. As a result, it qualifies as a biofuel. Internal combustion engines, or IC engines, use this combustion process.

What is a Displacement Reaction

Displacement reactions occur when a portion of one reactant is replaced by another. A replacement reaction is another name for it. As one reactant ion is replaced by another. Single displacement reactions occur when one element removes another from its salt or complex. Single replacement reactions are another name for them. General representations can also be written –

\[A + B – C{\rm{ }} \to {\rm{ }}A – C + B\]

Examples of Displacement Reaction

• The reaction between Calcium Iodide and Chlorine.

\[Ca{I_2} + C{l_2} \to {\rm{ }}CaC{l_2} + {I_2}\]

• The reaction of Zinc with Hydrochloric Acid.

\[HCl + Zn{\rm{ }} \to {\rm{ }}ZnC{l_2} + {\rm{ }}{H_2}\]

Decomposition Reactions

A decomposition reaction is a chemical reaction that occurs when one reactant breaks down into two or more products.

The 2 main categories of these reactions are as follows

• The reaction of Thermal Decomposition:

It is a decomposition reaction that is triggered by heat energy.

E.g. \(CaC{O_3} \to {\rm{ }}C{O_2} + CaO\)

When heated, calcium carbonate breaks down into calcium oxide and carbon dioxide. Quick lime, a crucial component in several industries, is made using this process.

• The reaction of Electrolytic Decomposition:

Electrical energy is used to give the activation energy for a breakdown in an electrolytic decomposition process. An electrolytic breakdown reaction, such as water electrolysis, is exemplified by the chemical equation:

E.g. \({H_2}{O_2} \to {\rm{ }}{H_2} + {O_2}\)

Summary

It can be concluded that a displacement reaction occurs when one reactant is partially displaced by another. Displacement reactions are also known as replacement or metathesis reactions. The two types of displacement reactions are double and single displacement reactions. In a process known as double displacement, cations and anions in the reactants exchange partners to generate products: When a single reactant partially replaces another, a single displacement reaction occurs.

Frequently Asked Questions

1. What are combustible substances?

Ans. The substances that are easily flammable and undergo combustion are called combustible substances. For Example – LPG, CNG, wood, paper, clothes, etc.

2. What causes an exothermic displacement reaction?

Ans. When one element in a molecule is replaced by another, a single-displacement reaction takes place. A chemical reaction either releases or absorbs energy. If energy is released during the process, it is exothermic. The bond formation is an exothermic process.

3. Mention two uses of decomposition reaction.

Ans. Two uses of decomposition reaction are-

• This is used in the formation of cement or calcium oxide.
• This is also used for welding purposes.

Introduction

Aufbau is a German word that means “building up.” Like a construction build-up from the ground up. Atoms are also filled with electrons in this manner. An atom has orbitals that are arranged in increasing energy level order. According to the Aufbau principle, electrons are filled in the order of increasing energy of the atomic orbitals. That is from the bottom to the top. This principle aids in the electronic configuration of atoms as well as the placement of electrons in orbitals. In all atoms, the orbital is always the first orbital to be filled with electrons. After filling this orbital, electrons are filled in orbitals further away.

Explain Aufbau Principle

Niels Bohr, a Danish physicist developed the principle. According to this principle, the increasing order of energy levels of atoms causes the filling of electrons in an atom. They are entering a perfect order that corresponds to the energy level of orbitals.  We can predict the electron configurations of atoms or ions by using this rule.

The Madelung rule or rule is also related to this rule. According to this rule, the filling of electrons in an atom occurs as the value of n+l increases. That is, the electrons are filled to a lower-valued orbital. Where n represents the principal quantum number value, and l represents the angular momentum quantum number value. This is known as the Madelung rule or the diagonal rule.

Some features of the Aufbau Principle

1. Electrons are assigned to the subshell with the lowest energetically available energy.
2. An orbital can only hold two electrons.
3. If two or more energetically equivalent orbitals (e.g., p, d, etc.) are available, electrons should be spread out before being paired up (Hund’s rule).

Some Exceptions 

Some elements exhibit exceptional behaviour in terms of the Aufbau principle. They are chromium and copper, respectively. According to the Aufbau principle, the electronic configuration of chromium is \(\left[ {Ar} \right]3{d^4}4{s^2}\). However, chromium’s electronic configuration is \(\left[ {Ar} \right]3{d^5}4{s^1}\). And this is because chromium achieves stability by having a half-filled orbital. Elements require a filled state at all times. A fully-filled orbital is always more stable. Even though a half-filled orbital has partial stability.

Copper’s electronic configuration is \(\left[ {Ar} \right]{\rm{ }}3{d^{10}}4{s^1}\) rather than \(\left[ {Ar} \right]{\rm{ }}3{d^9}4{s^2}\). This is due to the presence of a fully-filled d-orbital configuration, which provides additional stability.

Summary

An electronic configuration is present for all elements to locate electrons in orbitals. As a result, the chemical properties of elements can be explained. When combined with other rules, this can result in a proper electronic configuration. According to Aufbau’s principle, the filling of electrons in an atomic orbital occurs in the order of increasing energy of atomic orbitals. The elements chromium and copper are exceptions to this rule. Because they achieve a half-filled and fully-filled atomic orbital, these elements can be more stable.

Frequently Asked Questions

1. Define Hund’s rule of maximum multiplicity

For an orbital of the same sub-shell, the filling of electrons takes place in a way that all the electrons are singly occupied before pairing occurs. The pairing of electrons takes place only when all the subshells are singly occupied.

2. What do you understand by Pauli’s exclusion principle?

All the quantum number values are distinct for each electron present in an atom. This principle states that no two electrons in an atom can have an equal set of all the quantum number values. And thereby we can easily locate all the electrons in an atom.

3. What is the principal quantum number?

The number that deals with the energy and size of orbitals are a principal quantum number. It will explain how far an electron is from the nucleus. For example, the electronic configuration of Helium is \(1{s^2}\) so the principal quantum number is 1.

Introduction

The electronic configuration describes the distribution of electrons within an atomic subshell. An electron configuration is a summary of the prediction of the position of the electrons surrounding a nucleus. In every neutral atom, the electron number is the same as the proton number. Now we’ll arrange those electrons so that they form a ring around the nucleus, displaying their energy and the orbital type in which they are located. Electrons occupy orbitals in a specific order based on their energy.

What do you understand by Electron Configuration?

• The electronic configuration describes the distribution of electrons within an atomic subshell.
• Atomic electronic configurations follow a standard format in which each atomic subshell containing an electron is listed in ascending order.
• For high atomic numbers, the standard representation of electronic configuration can be quite lengthy. In some cases, an abbreviated/condensed symbol may be used instead of the standard representation.
• The electron configuration of Na, for example, is \(1{s^2}2{s^2}2{p^6}3{s^1}\).

How Subshells are important for Electron Configuration?

• The azimuthal quantum no., represented by the letter “l,” determines the distribution of electrons into subshells.
• The magnitude of the principal quantum no., n, dictates the magnitude of this quantum number. As a result, when n equals 4, four distinct subshells can exist.
• For n = 4, the s, p, d, and f subshells correspond to l=0, 1, 2, 3 quantities.
• Equation 2(2l+1) gives the maximum number of electrons that a subshell can hold.
• The s, p, d, and f subshells can hold a maximum of 2, 6, 10, and 14 electrons, respectively.

Atomic Electronic Configuration Representation

This section provides examples of a few elements’ electronic configurations.

• The electron configuration of hydrogen has an atomic number of one. As a result, an H atom has one electron, which will be assigned to the subshell of the first shell/s orbit. \(1{s^1}\) is the electronic configuration of H.
• The electron configuration of chlorine

Cl has the atomic number 17. As a result, its 17 electrons are distributed as follows:

The K has two electrons.

The L has 8 electrons and the M has 7 electrons.

The electron configuration of Cl is depicted below. It is written as \(1{s^2}2{s^2}2{p^6}3{s^2}3{p^5}\).

Filling Atomic Orbitals

The following concepts govern how electrons are occupied in atomic orbitals.

Aufbau Principle

“The energy of an atomic orbital is calculated by adding the principal and azimuthal quantum numbers, and according to the Aufbau principle, electrons begin in relatively low energy orbitals and progress to higher energy orbitals.”

Pauli Exclusion Principle

“Only electron pairs with opposite spins can be carried in an atomic orbital, and no two electrons in the same atom have the same values for all four quantum numbers. If two electrons have the same principle, azimuthal, and magnetic numbers, they should have opposing spins.”

Hund’s Law

“Before a second electron is placed in an orbital, each orbital in a specific subshell is said to be entirely filled by electrons.”

Summary

It can be concluded that Electron configuration is the depiction of electron distribution inside an element’s atomic shells. Because the electrons are mathematically positioned in these subshells, the configuration aids in determining their position. The periodic table categorises elements based on their electron configurations. These make up the s, p, d, and f-block elements. The maximum number of electrons that can fit in a shell is determined by the principal quantum number (n). The azimuthal quantum number, represented by the letter “l,” governs the distribution of electrons into subshells.

Frequently Asked Questions

1. Why are specific electron configurations required for elements?
Ans. Electron configurations can shed light on an atom’s chemical behaviour by identifying its valence electrons. It also aids in the organisation of elements into different blocks such as s, p, d, and f blocks.

2. Describe the significance of electron configuration.
Ans. The significance is as follows:

They aid in determining the reactivity state of an atom.

It aids in the identification of both chemical and physical properties.

It foretells an atom’s magnetic properties.

3. For n=3, which subshells are present?
Ans. Each orbital can hold a maximum of two electrons, and there are four subshells present- s, p, d, and f for n=3. The maximum number of orbitals corresponding to the s, p, d, and f subshells is 1,3,5, and 7.

Introduction:

Gypsum powder is called Plaster of Paris which is white. Gypsum is very common in Paris, which is how it earned its name. Gypsum is commonly heated to a higher temperature to make plaster of Paris. This is a dry powder that is mixed with water and hardens. When drying, this becomes flexible. In the field of architecture, plaster of Paris is used in a variety of ways. A famous substance, found in gauze bandages and sculpture materials is called the plaster of Paris.

Components of Plaster of Paris

Gypsum that has been roasted and milled into a fine powder is called plaster of Paris. Chemically it is written as\(\;CaS{O_4}.{\rm{ }}\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/\kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} {H_2}O\). Heat is generated as calcium sulfate transforms from its more soluble form\((CaS{O_4}.{\rm{ }}\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/\kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} {H_2}O)\) to its comparatively insoluble state\((CaS{O_4}.{\rm{ }}2{H_2}O)\) when water is added.

Properties of Plaster of Paris

1. POP is an ideal material for forming moulds because it doesn’t stretch or break when dried. Beautiful plasterworks, including cornices, are frequently constructed and maintained with this technique.
2. It is neither flammable nor combustible. It has a relatively weak chemical reactivity but, in extreme cases, can operate as an oxidizing agent. Hazardous sulfur oxides are produced during decomposition at moderately high temperatures. It creates gypsum \(CaS{O_4}\) by a slow and exothermic reaction with water or air moisture.

Washing Soda

Properties

A white, odorless dust is called washing soda. It has a chemical name termed sodium carbonate decahydrate, and its formula is\(\;N{a_2}C{O_3}.10{H_2}O\).

Its water-absorbing nature allows it to absorb moisture from the surrounding atmosphere. It is very soluble in water and creates a very basic solution.

Preparation

Through Solvay’s method, washing soda is produced. It starts as sodium bicarbonate, which is heated to become sodium carbonate. Finally, sodium carbonate is recrystallized to generate washing soda.

\[NaCl + N{H_3} + C{O_2} + {H_2}O{\rm{ }} \to {\rm{ }}NaHC{O_3} + N{H_4}Cl\]

\[2{\rm{ }}NaHC{O_3} \to N{a_2}C{O_3} + {H_2}O + C{O_2}\]

\[N{a_2}C{O_3} + 10{H_2}O \to {\rm{ }}N{a_2}C{O_3}.10{H_2}O\]

Baking Soda

Baking soda or bicarbonate of soda, also termed sodium bicarbonate,  is a chemical substance with the formula \(NaHC{O_3}\). Bicarbonate anion (\(HC{O_3}^ – \)) and the sodium cation (\(N{a^ + }\)) combine to form baking soda.

Properties

1. A white crystalline substance with a density of around 2.2 g/mL is known as sodium hydrogen carbonate. It tastes alkaline and is only slightly soluble in water. With an increase in temperature, sodium hydrogen carbonate becomes more soluble.
2. It is well known that baking soda can neutralize odors. Baking soda is therefore widely used to remove false odors from freezers and other closed spaces.

Preparation

In the reaction of a saturated sodium carbonate solution and carbon dioxide, sodium hydrogen carbonate (baking soda) is formed. Due to its low solubility, the white powder of sodium hydrogen carbonate isolates out.

Summary

Gypsum (calcium sulfate) powder and water are combined to create the plaster of Paris, which quickly dries. Medical professionals use plaster of paris to fix broken bones. Orthopedic casts still frequently utilize plaster of Paris. Washing soda’s pH is higher than that of baking soda. Baking soda, like the Arm & Hammer variety containing sodium bicarbonate, is edible and safe to use on human skin. It is not advisable to consume, breathe, or put alkaline washing soda on the skin.

Frequently Asked Question

1. How to make the plaster of Paris waterproof?

Ans: When the plaster of Paris is cured, it transforms into a highly porous material that will absorb any water that comes into contact with it. Plaster of Paris must have as many surface gaps as possible blocked to behave as waterproof for outdoors or brief exposure to water.

2. Is baking soda a blood pressure raiser?

Ans: Hypertension: Sodium bicarbonate may raise blood pressure. The use of sodium bicarbonate should be prohibited by individuals who already have high blood pressure. Low blood potassium levels: Sodium bicarbonate may decrease blood potassium levels.

3. What occurs if the plaster of Paris is left out in the open?

Ans: Plaster of Paris is a kind of rapid gypsum plaster that hardens when moistened and left to dry as it reacts with the moisture in the atmosphere to form gypsum. It is composed of a fine white powder termed calcium sulfate hemihydrate.

Introduction

An atom’s energy changes due to electron affinity. A neutral atom gains energy and a negative charge when electrons are added to its outer shell. To stabilise its octet, an element gains electrons. When an element accepts or loses an electron, energy is released. When an element accepts an electron to form a compound, it releases energy, which is referred to as an exothermic reaction. The energy is released in an exothermic reaction in order to attract the electron by a nucleus from another element. When an element loses an electron, it absorbs energy, a process known as endothermic. An atom gains energy when it loses electrons.

What do you mean by Electron Affinity?

When atoms accept electrons, they emit energy, which is referred to as an exothermic reaction. Atoms that lose an electron in a chemical reaction, on the other hand, absorb energy and are known as endothermic reactions. The ability to accept an electron is referred to as electron affinity. When a neutral gaseous atom accepts an electron, it gains a negative ion charge. The first electron affinity is always negative, while the second is always positive. It is difficult to measure the electron affinity of an atom. It is determined by the energy released by ionic compounds. The electron affinity is also measured by an atom’s tendency to act as an oxidising or reducing agent. It is measured in kilojoules/moles. Electron affinity is symbolised by EA.

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Factors Influencing Electron Affinity

The atomic size of the element, the nuclear charge on the molecules, and the electronic configuration of atoms are all factors that influence a molecule’s electron affinity.

1. Atomic size: Atoms with smaller sizes have greater electron affinity than atoms with larger sizes. The nucleus of smaller atoms is more attractive to electrons than the nucleus of larger atoms. As the atom’s size increases, the outer shell becomes further away from the nucleus, and the attraction for electrons in the outer shell decreases. 
2. Nuclear Charge: The nuclear charge influences electron affinity as well. As the charge on an atom increases, so does the attraction in electrons, and thus the electron affinity. When a molecule is already charged, electron repulsion increases, and the pull from the nucleus increases, resulting in increased electron affinity in charged ions.
3. Shielding Effect: As the screening effect on an atom’s inner shell is reduced, the electron affinity increases.
4. Electronic Configuration: The electronic configuration also affects electron affinity. Because elements with full octets have zero tendencies to accept electrons, electron affinity in inert gases is zero. The electronic configuration is crucial in electron affinity. Metals have a lower affinity for electrons than non-metals due to their electronic configuration.

Summary

The ability to accept electrons in gaseous form and form an anion is referred to as electron affinity. The process of accepting electrons generates energy, which is why it is referred to as an exothermic process. When we move from group to group, the electron affinity decreases and increases when we move from period to period. It is denoted by the symbol EA and measured in Kilojoules per Mole (KJ/Mol). Because of electron-electron repulsion, the first electron affinity is always less than the second electron affinity. The atomic size, electronic configuration, screening effect, and nuclear charge of elements all influence electron affinity.

Frequently Asked Questions

1. Why do noble gases have no electron affinity?

Ans. Noble gases have zero electron affinity because their octet is complete, and they do not have an affinity for electrons. As a result, noble gases have no electron affinity.

2. Why does group 17 have such a strong electron affinity?

Ans. Because the halogens are small and have more electrons in the outer shell, the elements of the halogens group have a high electron affinity. A halogen would rather accept an electron than lose seven electrons to complete its octet.

3. Why does fluorine have a lower electron affinity than chlorine?

Ans. Because the atomic size of fluorine molecules is smaller than that of chlorine molecules, the outer shell of fluorine is already filled with electrons, and the nucleus is much closer to the outer shell, the electron repulsion is greater than the force of attraction of the nucleus when an electron is placed in the outer shell of fluorine molecules compared to chlorine molecules.

Introduction

How does a mobile phone’s battery charge when plugged into its charger, or how does the cell in a TV remote control work? All of these questions have answers in the scientific field of electrochemistry. Electrochemistry is the study of both the use of electricity to conduct non-spontaneous chemical reactions and the production of electricity through chemical reactions. To achieve the goal, cells are used. Cells are components that initiate chemical reactions that produce or generate electricity.

What is an electrochemical reaction?

An electrochemical reaction is any process that is initiated or accompanied by the flow of electrical current, and typically involves the transport of electrons between two substances—one solid and one liquid. An electrochemical reaction occurs when a solid electrode and a material, such as an electrolyte, interact. This flow causes the reaction to release or absorb heat by producing an electric current to pass across the electrodes. When, for example, two electrodes in contact with one another initiate an oxidation and reduction (redox) reaction, the oxidation number of all the atoms involved in the reaction changes.

The process of electrochemical reaction

The properties of the negatively charged\(\;{e^ – }\)determine how matter interacts with an electric current as it flows through a system. Because protons are positively charged matter units found in elements, groups of atoms, or molecules, the electron, the fundamental unit of electricity, is drawn to them. This attraction is comparable to the chemical attraction that particles have for one another. Every chemical reaction changes the structure of an atom’s electrons, and the liberated electrons can either join with matter particles to form reductions or be ejected by them (oxidation). 

Faraday’s rules define the quantitative relationship between a free electron in a current flow and the atoms of a substance, where they cause a reaction. Electrochemical process components are also known as ionic conductors or electrolytes.

What is an Electrochemical cell?

An electrochemical cell is a system that can generate electrical energy from spontaneous chemical reactions. The chemical processes that occur during this process are known as redox reactions. During redox reactions, electrons are transferred between chemical species. They are also referred to as galvanic or voltaic cells. An electrochemical cell is illustrated by the Daniell cell.

The following are the essential components of an electrochemical cell:

1. An electrolyte is a substance found between electrodes that, when dissolved in polar solvents such as water, produces freely flowing ions, resulting in an electrically conducting solution.
2. Electrodes are solid electrical conductors that are used in electrochemical cells and are made of good conductors, such as metals.
3. They are available in two varieties:
4. The Cathode is the area of the cell where reduction takes place.
5. The anode is the part of the cell where oxidation takes place.
6. A salt bridge connects the oxidation and reduction halves of an electrochemical cell, completing the circuit. It is brimming with KCl and other saturated salt solutions. The bridge is required for the ions in the solution to flow between half-cells.

What are the different kinds of electrochemical cells?

There are two major kinds:

1. Galvanic Cell / Voltaic Cell: Chemical energy is converted to electrical energy in these electrochemical cells.
2. Electrolytic Cell: In these cells, electrical energy is converted to chemical energy.

Explain its operation

• Working Principle

The fundamental operating principle of an electrochemical system is the transfer of\(\;{e^ – }\)produced by a redox reaction occurring in it, which results in an electric current.

• Working Mechanism 

When the switch is turned on after an electrochemical cell has been fully assembled, the galvanometer of the external circuit deflects. The needle of the galvanometer moves in the direction of the beaker containing the copper sulphate solution. It indicates that the current has changed direction from the copper sulphate solution beaker to the zinc sulphate solution beaker. When the circuit is completed, a change occurs that causes zinc atoms in the zinc electrode to oxidise and Cu atoms in the copper rod to reduce. Zinc releases two electrons, which copper accepts via an external circuit.

Full redox reaction: \(\;Zn{\rm{ }}\left( s \right){\rm{ }} + {\rm{ }}C{u^{2 + }}\left( {aq} \right){\rm{ }} \to {\rm{ }}Z{n^{2 + }}\left( {aq} \right) + Cu{\rm{ }}\left( s \right)\;\;\;\)

Some applications of Electrochemical Cell

1. Many non-ferrous metals are electro-refined in metallurgy using electrolytic cells, yielding very pure metals such as Pb, Zn, Al, and Cu. 
2. It is used to recover pure Na metal from molten NaCl by storing it in an electrolytic cell.
3. Silver oxide batteries are used in hearing aids.
4. Thermal batteries are used in Navy gadgets for military applications.

Applications of Electrochemistry

1. Electrical batteries are created using the concept of cells. A battery is a device used in science and technology that stores chemical energy and provides electrical access to it.
   1. Applications in defence (thermal batteries)
   2. Digital cameras (Li batteries)
   3. Audio equipment (silver-oxide batteries)
2. Electroplating is used for a variety of purposes, including the production of jewellery and the corrosion protection of certain metals.
3. Electrochemistry is required in a variety of industries, including the chlor alkali industry.

Summary

Electrochemistry is a fascinating subject. Electrochemical reactions are important to comprehend because they have significant academic and practical implications. Understanding the responses allows us to better understand how everyday objects such as a battery or cell work. Chemical energy can be used to generate electrical energy in electrochemical cells, and electrical energy can be used to generate chemical energy.

Frequently Asked Questions 

1. What factors affect electrode potential?

Ans. The reduction potential refers to an electrode’s ability to accept electrons, whereas the oxidation potential refers to an electrode’s tendency to lose electrons. The potential of an electrode is determined by the temperature and metal ion concentration at its surface.

2. Can a zinc pot be used to store copper sulphate solution?

Ans. Copper has a lower reactivity than zinc. As a result, zinc can remove Cu from its salt solution. If the\(\;CuS{O_4}\) solution is kept in a zinc container, copper will be removed from the solution.

\[Zn + CuS{O_4} \to ZnS{O_4} + Cu\]

As a result, the copper sulphate solution cannot be stored in a zinc pot.

3. In the SI system, what is the emf measurement?

Ans. The energy contained in a battery per Coulomb of charge is known as the electromotive force, EMF has a SI unit of volts, which is equal to joules per coulomb.

Introduction

The different forms of \({H_2}O\) in three different phases are ice (solid), water (liquid), and gas (vapour). The intermolecular spaces in solid particles are very low, they are tightly bound to each other. The intermolecular spaces are comparatively higher in liquids and become maximum in vapours. With the increase in temperature, the kinetic energy of the molecule increases, and the intermolecular interaction between the particles decreases. That is why, on the application of heat, ice is transformed into water and then to vapour Melting and boiling depend on the pressure of the environment. On this basis, a pressure cooker is used to make food in daily life.

What is the melting point of ice?

The melting point of a substance is the temperature at which a solid and liquid phase may coexist in equilibrium, and the temperature at which matter changes from solid to liquid form. The term applies to pure liquids and solutions. The melting point depends on pressure, so it should be specified. This melting point of ice is 0℃. If the temperature increases beyond the melting point, it doesn’t increase the temperature of the matter. Rather, it helps to transform the ice completely into the water. This is known as the ‘latent heat of fusion’ of ice.

What is the boiling point of water? 

With the addition of further heat, the water (liquid) reaches its vapour phase (gaseous state) at a particular temperature. This is the boiling point of water. The boiling point of water is 100℃. The heat that helps to convert the whole water into the gaseous state is known as the ‘latent heat of vaporisation’ of water. 

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Method to determine the melting point of ice:

The melting point of ice is 0℃. It is determined in a laboratory in the following steps-

• Some ice cubes are taken in a beaker and a thermometer is dipped in it. 
• Heat is applied gently by the Bunsen burner below the beaker.
• The changes in the state of the ice are monitored every minute and the temperature is recorded at which the whole ice is transformed into water. 
• The temperature at which the ice starts melting is noted as \({t_1}\) and the temperature when all the ice melts is noted as \({t_2}\).
• Then the average of \({t_1}\) and \({t_2}\) is calculated. This mean temperature is known as the melting point of ice. 

In this way, the melting point of ice is determined.

Method to determine the boiling point of water:

The water boils at 100℃. It is measured in the laboratory in the following steps-

• A suitable amount of water is taken in a round bottom flask and its mouth is sealed properly with a rubber cork. 
• A thermometer is inserted through a hole in the cork into the r.b flask without touching the water surface. 
• The r.b flask is then heated by a Bunsen burner, and placed on the bottom of a wire gauge supported by a tripod stand. 
• A thermometer reading is taken at a certain interval and the temperatures are recorded. 
• A thermometer reading is taken continuously throughout the boiling of water. 

In such a way, the boiling point of water is measured. 

Factors influencing the melting point and boiling point: 

Factors	Melting point	Boiling point
Pressure	With an increase in pressure, the melting point decreases.	With an increase in pressure, the boiling point increases.
Impurities	Impurities like soluble salts decrease the melting point.	The presence of impurities increases the boiling point.
Size of substance	With an increase in the size of the substance, the melting point increases.	With an increase in the size of thesubstance, van der Waals interaction increases henceboiling point increases.
Intermolecular forces	The melting point increases with an increase in intermolecular interactions, as more energy is needed for bond cleavage.	The stronger the intermolecular forces, the lower the vapour pressure. As a result, the boiling point increases.

Summary: 

The temperature at which ice starts to melt into water is called the melting point of ice (0℃). And the temperature at which water starts to form vapour is termed the boiling point of water (100℃). Intermolecular interaction decreases while moving from ice to water to gas. So, through the melting point of a solid and the boiling point of the liquid, one can have an idea about the extent of interaction among the particles. Moreover, the presence of impurities can be determined from the melting and boiling point values. 

Frequently Asked Questions 

1. Can the size of a molecule affect the melting point value?

Ans: With an increase in size, the van der Waals forces among the molecules increases. As the melting point highly depends on attractive forces i.e. van der Waals interaction, the size can impact the melting point value of the molecule. 

2. Why is the boiling point of water always considered to be 100℃?

Ans: The liquid will start to boil once the vapour pressure of the liquid matches the atmospheric pressure in the region. The point at which water boils is highly influenced by the vapour pressure. At 100℃, the vapour pressure around sea level equals the surrounding air pressure. So, it is considered the boiling point of water. 

3. How can one identify a substance by its melting point?

Ans: Various organic, as well as inorganic compounds, can be identified from their melting point. Also, the extent of purity can be known from their melting point values. If the substance is pure, it will show a sharp melting point instead of a range of melting points in case of an impure substance. 

Introduction

A “mixture” is a combination of two or more substances, such as water and sand, salt and water, or a solution of two solutes, for example. These mixtures are not chemically linked. Hand-picking, winnowing, filtration, distillation, and other techniques are used to separate them. The mixture can be solid in solid, liquid in liquid, gas in gas, and so on. Seawater is also a salt-water mixture. The “evaporation method” is used to separate salt from seawater. Different techniques are used to separate different types of mixtures.

Methods of Separating Mixtures:

Depending on the type of mixture, there are various methods for separating it. In 1840, some prospectors used water to separate gold from a mud mixture; the mud containing gold was filled with water in a pan.

After a while, the pan was twisted to remove the dissolved material, and gold settled in the pan due to its weight. Panning is the process of separating gold from water.

Substances in our environment exist as mixtures, of which there are two types: “homogenous” and “heterogeneous” mixtures.

Different techniques are used to separate them.

Hand-picking: 

The hand-picking method is used to separate the mixtures that are less in quantity and the size of the particle is big. It is usually used to separate stones from grains, rice pulses, etc at home and groceries shops. In this type both the components are in solid form, these are big enough to separate them by hand.

Threshing:

This method is widely used to separate grains from twigs. Farmers use this method to separate hard wheat, rice, pulses, and other grains from their stalks. When food grains reach maturity, the farmer harvests and dry them in the field.

Winnowing:

This method is used to separate the husk from grain or pulses with the help of “ wind” that’s why it is named “winnowing”. 

• In this method, the grains separated by the threshing method contains small twigs, and a husk that is quite thin and light in weight. 
• The grains containing husk are taken in a winnowing basket. The farmer stands at a particular height, taking that basket in the direction of the wind. 
• The farmer falls the grains, the husk, and the twigs get separated by the flow of wind and the grains get cleaned.

Evaporation

1. To separate the mixture into liquid form, “the evaporation technique” is used. The volatile material evaporates, leaving behind a non-volatile solid in the container.
2. The mixture is heated in this method until the liquid portion of the mixture evaporates.
3. The mixture’s solid component is left in the container.
4. This method separates salt from seawater.

Distillation

The “distillation method” is used to separate two or more mixed liquids.

1. A “distillation apparatus” in this method is a plant that contains a flask, a thermometer, a condenser, and a collecting flask (distillate).
2. The mixture is heated to a specific temperature in the distillation flask.
3. The liquid begins to boil and turns into vapour.
4. This vapour is collected in a “distillate” after being condensed in a condenser.

Filtration 

It is a common technique for separating liquids from insoluble solids.

1. The “filter paper” is used in the filtration process to separate liquid from the mixture that is large enough to become trapped in the porous material.
2. To separate water from a sand and water mixture.
3. Heavy impurities are settled down during the sedimentation process.
4. The first liquid, which is above, is then slowly separated from the flask.
5. This method is used to separate mud and water mixtures.

Summary

The elements in the environment are found in combination with other elements. These are both homogenous and heterogeneous mixtures. The mixture can exist as a liquid, solid, or gas. The two materials are not chemically bonded. Depending on the type of mixture, different methods are used to separate it.

Frequently Asked Questions

1. How are the essential oils extracted from the flowers?

Ans. Steam distillation is used to separate the essential oils. The liquid is converted into steam in this process, and the steam vaporises the material with it before being condensed and separated in a retort.

2. Which mixture is separated using cryogenic distillation?

Ans. This method is used to separate the acid gas mixture from the gaseous mixture, LPG, and is similar to removing CO2 from LPG.

3. How are fatty acids, resins, and wax separated from the mixture?

Ans. Drugs, esters, fatty acids, tocopherols, resins, and wax are separated from mixtures using short-path distillation.