Category: Chemistry

Introduction

Molar masses that are calculated to be too high or too low than the actual molar mass are deemed abnormal molar mass.  They are calculated using the colligative characteristics. Among the colloquial features are a higher osmotic pressure, a lower vapour pressure, a lower freezing point, and a higher boiling point. Van’t Hoff factor is used in such cases to find the actual molar mass. 

What is the Van’t Hoff Factor?

• Because the actual molar mass of a substance is not always equal to the sum of the atomic masses of the atoms making up the substance, a quantity called the Vant Hoff factor is employed to account for this discrepancy. This occurs because the arrangement of atoms in a substance is not constant. To make sense of this variation in setup, the Vant Hoff factor is employed.
• It is denoted by the symbol i. A material’s degree of association or dissociation in a fluid is the relevant factor. When something that isn’t electrolytic dissolves in water, the value of i will typically always equal 1. When dissolving in water, the number of ions (i) remains constant regardless of how many atoms (N) of the substance are dissolved.
• Jacobus Henricus Van’t Hoff, the first recipient of the Nobel Prize in Chemistry, is honoured with the naming of this constant. In the case of electrolytic fluids, it is important to note that the measured factor will be smaller than predicted. A greater divergence is seen at higher ion charges.

Effects of Association/Dissociation

• The combining of 2 or more substances to produce a single object is known as an association. Carboxylic acids show a high degree of association through hydrogen bonding.

• Dissociation is the process by which a substance is split up into its constituent ions. Sodium chloride breaks down into Cl- and Na+ ions when exposed to water.
• The following table summarizes the consequences of a solute’s dissociation or even association on the Van’t Hoff factor. 

Abnormal Molar Masses

An irregularity in molecular mass occurs in the following cases:

•  The dissolution of solute components into many ions increases the total particle content and hence enhances the colligative features of the mixture.
• Due to the inverse relationship between molar mass and colligative properties, we anticipate a smaller final outcome.
• Since the number of solute particles is reduced as a result of their interactions, colligative characteristics are also reduced. Readings of molar mass in this scenario will be higher than expected.

Summary

Molar mass is the overall no. of moles available in a solution following solute association or even dissociation.  Abnormal molar mass occurs when the molar mass is less than or more than the predicted value. The Van’t Hoff factor gives accurate data on how solutes affect the colligative properties of fluids. It will always be smaller than one for solutes that show an association. The factor will be greater than one for dissociating solutes. It will be one for particles that demonstrate no association or even dissociation.

Frequently Asked Questions

1. What is the difference between the Vant Hoff factor and the activity coefficient? 

Ans. The Vant Hoff factor is a measure of the degree of dissociation of a solute in a solution. The activity coefficient is a measure of the degree of ionization of a solute in a solution.

2.Does van’t hoff factor depends on solvent?

Ans. Since colligative properties depend only on the number of solute particles, there is no affect of solvent. Hence vant hoff factor does not depend on the solvent. 

3. Does Vant hoff factor always have an integral value?

Ans. The van’t Hoff factor is a positive number, but it isn’t always an integer value. It is 1 for a solute that does not dissociate into ions, greater than 1 for most salts and acids, and less than 1 for solutes that form associations when dissolved.

Introduction

Among the several intermolecular forces that exist, Van der Waals forces are notable. Johannes Diderik van der Waals, a Dutch scientist, proposed them in 1873 and so they bear his name. When compared to other intermolecular forces like hydrogen bonding and ionic bonding, Van der Waals forces are weak. Nonetheless, they continue to play a significant role in numerous branches of chemistry and physics.

In contrast to covalent and ionic bonding, which are both based on shared electrostatic repulsion between atoms, weak interactions are facilitated by correlations between the wildly varying polarisations of neighbouring particles (a consequence of quantum dynamics).

What are Van Der Waals forces?

Van Der Waals forces refer to the attractive and repulsive interactions that act between molecules and between atoms. The polarisation variations of neighbouring particles create these bonds, setting them apart from covalent and ionic interactions.

As a result of transient dipoles formed by the unequal distribution of electrons, molecules are attracted to one another via Van der Waals forces. This may occur due to the proximity of two molecules or the presence of a persistent dipole in one of the molecules. Because of the dipoles, the molecules are drawn to each other via a van der Waals force.

Characteristics 

• Covalent bonds involve electron sharing, while ionic bonds require one or both atoms to give up an electron. They’re both attracted to each other with a force that’s orders of magnitude stronger than Van Der Waals’.
• Multiple independent interactions compose them, making them cumulative.
• These forces do not have a direction and are thus impossible to fully exhaust.
• They do not vary with variations in temperature. This is because the amplitude of these forces is greatest when the interacting molecules or atoms are in close proximity to one another, and they only act across a short distance.

Types of Van Der Waals Forces

London Dispersion Forces

When the electrons in two neighbouring atoms are in locations that cause the atoms to form temporary dipoles, an attractive attraction known as the London dispersion force is produced. An induced dipole-induced dipole attraction is another name for this force.

Dipole-Dipole interaction

Two polar molecules attract one another due to the attraction forces of their constant dipoles. These dipoles are formed because of the disparities in electronegativity between neighbouring atoms.

Hydrogen Bonds

These are unique dipole-induced dipole interactions between hydrogen atoms and highly electronegative atoms such as oxygen, nitrogen and fluorine. 

Debye forces

These forces emerge when attractive Coulomb forces between permanent dipoles are outweighed by the strength of interactions between the permanent dipoles and other atoms/molecules.

Factors affecting Van Der Waals forces

Nature of element

The nature of an element or a non-metal is determined by the strength of its Van Der Waals forces. Elements or non-metals found in a liquid or gaseous state rely on these forces, whereas some metals use cohesive forces.

Electron count in an atom/molecule

In a periodic table, the atomic radius and the number of electrons held by each nucleus both grow as one descends from group to group There are more opportunities for transient dipoles to occur when the number of electrons is high. When there are many dipoles in a solution, the Van Der Waals force between them becomes greater.

Shape of molecule

The chemical structure of a molecule—whether it is branched or unbranched—can affect the strength of intermolecular forces, which in turn affects boiling points. 

Size of an atom

Attractive bonds have different strengths depending on the sizes of the atoms involved. The intermolecular interactions between atoms strengthen as the size of an atom grows.

Shape of an atom

The strength of an atom’s intermolecular forces depends on the shape of its molecules. Thin molecules have more potential to develop temporary dipoles than short, fat ones.

Applications of Van Der Waals forces

• Van Der Waals forces aid in protein folding and further solidify the protein in its final structure.
• They also facilitate the bonding of graphenes within graphite by acting as lubricants.
• Research and development in fields like supramolecular chemistry, nanotechnology, and polymer synthesis.
• For the most part, they are responsible for keeping the inert gases in a solid or liquid form.
• Due to the attracting force exerted at the ends of their feet, geckos can quickly and easily scale smooth surfaces.
• Spiders are similar in structure.

Summary

Molecules are attracted to one another by forces known as van der Waals forces. The two most common kinds of van der Waals forces are the weak London Dispersion Interactions and the larger dipole-dipole forces. They are influenced by many different things, such as the elements themselves, the molecular and atomic structures they are made of, and the sizes and shapes of their constituent parts.

Frequently asked questions

1. How do Van de Waal forces affect the viscosity of a substance?

Ans. Van de Waal forces can increase the viscosity of a substance by increasing the attraction between molecules, which makes it more difficult for them to move past each other.

2. Write the equation of Van Der Waals forces.

Ans. (P+n2a/V2) (V-nb) ＝ nRT

The above equation demonstrates the main two kinds of properties present – the volume of both elements and the attractive forces between them.

3. What is the use of the Van Der Waals equation?

Ans. The Van Der Waals equation is helpful in calculating an actual value in the case of non-ideal gases.

Introduction

Due to the distinctive adaptations made by each cell type to the ecosystems they live in, plant cells and animal cells, two forms of eukaryotic cells, differ in a number of ways. A nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, and mitochondria can be found in both plant and animal cells. Basic life processes like protein synthesis, energy production, and waste elimination are carried out by these organelles. While there is numerous similarity between both, there are also several significant distinctions that show how each type of cell has uniquely adapted to its environment and role.

What is a cell?

The fundamental unit of life and the foundation of all living things is the cell. Robert Hooke used the term “cell” in 1665 to refer to the discrete entities he saw in a cork while using a microscope. Each metabolic process required for the survival and expansion of the organism is carried out by a cell.

Plant cell function

The main function of a plant cell is to carry out the metabolic processes necessary for the survival and growth of the plant. These processes include:

1. Photosynthesis: Plant cells transform photosynthesis, which is then stored as sugar. Chloroplasts, specialized organelles present in plant cells, carry out this process, which is the plant’s main source of energy.
2. Cell division and growth: Plant cells divide and grow to allow the plant to increase in size and produce new tissue.
3. Transport: Plant cells are responsible for transporting water, minerals, and other materials within the plant. This is accomplished through the movement of substances across the cell membrane and through specialized structures such as the endoplasmic reticulum and Golgi apparatus.
4. Storage: Plant cells store nutrients, waste, and other materials in specialized structures such as vacuoles.
5. Waste management: Plant cells are responsible for removing waste and toxins from the plant.

Animal Cell Function

The function of an animal cell is to perform all of the metabolic processes needed for the survival and growth of the animal. These processes can be grouped into several main categories:

1. Energy production: Cells must produce energy to carry out their metabolic processes. This is usually accomplished through cellular respiration, a process that takes place in the mitochondria and generates energy in the form of ATP.
2. DNA replication and protein synthesis: Cells must be able to replicate their DNA and synthesize new proteins to allow for growth and repair.
3. Response to signals: Cells must be able to respond to signals from their environment, such as changes in temperature, light, or chemicals.
4. Communication with other cells: Cells must be able to communicate with other cells to coordinate their functions and work together as a unit.
5. Contraction and movement: Some animal cells, such as muscle cells, are specialized for contraction and movement.

Difference Between Plant Cell And Animal Cell

Plant cells and animal cells are both eukaryotic cells, but there are several important differences between the two that are due to the unique adaptations of each cell type to the environments they live in. Some of the main differences between plant and animal cells include:

1. Cell Wall: Animal cells lack a cell wall, but plant cells have a hard cell wall formed of cellulose that offers support and protection.
2. Size: Plant cells are larger with rectangular shapes while animal cells are smaller and rounder.
3. Vacuoles: Plant cells have large central vacuoles that store water and waste, while animal cells have smaller, more numerous vacuoles.
4. Chloroplasts: Plant cells contain chloroplasts, which are specialized organelles that carry out photosynthesis, while animal cells do not contain chloroplasts.
5. Mitochondria: Both plant and animal cells contain mitochondria, but animal cells typically have more mitochondria to meet their higher energy needs.
6. Endoplasmic Reticulum and Golgi Apparatus: Both plant and animal cells have endoplasmic reticulum and Golgi apparatus, but they are more highly developed in plant cells.

Summary

A cell performs every metabolic task necessary for the organism to survive and grow. Even though both animal and plant cells are eukaryotic, there are several notable differences between the two as a result of the unique environmental adaptations that each type of cell has made. Plant cells have a strong cell wall made of cellulose that provides support and protection while animal cells do not have one. Compared to plant cells, which are often larger and more rectangular, animal cells frequently have a smaller, more spherical shape.

Frequently Asked Questions 

1. Which cell organelles are absent from animal cells and only found in plant cells?

1. Animal cells lack several cell organelles that are only found in plant cells, including:
2. Cell wall: Unlike animal cells, which lack a cell wall, plant cells have a rigid cell wall made of cellulose that serves as support and protection.
3. Chloroplasts: Animal cells do not have chloroplasts, which are specialized organelles that perform photosynthesis in plant cells.
4. Animal cells have smaller, more numerous central vacuoles, but plant cells have a larger central vacuole that stores water and waste.

2. Why prokaryotic cell different from a eukaryotic cell?

Prokaryotic cells and eukaryotic cells differ in several important ways:

1. Size: Compared to eukaryotic cells, prokaryotic cells are smaller and have a simpler structure. They only have a single circular chromosome for their genetic makeup, and they lack a nucleus or any other membrane-bound organelles. On the other hand, eukaryotic cells are significantly bigger and more complicated, with a distinct nucleus and some additional organelles that are attached to membranes.
2. Genetic Material: Prokaryotic cells have a single chromosome of circular DNA located in the cytoplasm, while in eukaryotic cells it’s in the nucleus.
3. Cell Wall: Prokaryotic cells are with rigid cell walls made of peptidoglycan, while eukaryotic cells have a more complex cell wall or a plasma membrane.

3. Name the different types of plastids.

Plastids are membrane-bound organelles found in plant cells and some protists. There are several different types of plastids, including:

1. Chloroplasts: Chloroplasts are plastids that contain chlorophyll and are responsible for carrying out photosynthesis.
2. Leucoplasts: Leucoplasts are plastids that are not involved in photosynthesis and are found in cells that do not need to produce food. They can function as starch or oil storage organelles, or they can produce and store pigments.
3. Chromoplasts: Chromoplasts are plastids that produce and store pigments, such as carotenoids, which give plants their yellow, orange, and red coloration.
4. Amyloplasts: Amyloplasts are plastids that store starch, which is a source of energy for the plant.

Introduction 

Atrial natriuretic factor (ANF) is a hormone produced by the heart that regulates blood volume and blood pressure. ANF is produced in the atria (the upper chambers) of the heart in response to increased pressure within the heart or increased blood volume.

Once released into the bloodstream, ANF works on the kidneys lead to increase in the excretion of salt and water, which reduces blood volume and blood pressure. ANF also acts on the blood vessels to cause them to relax and dilate, which further reduces blood pressure. Elevated levels of ANF are often seen in people with heart failure, indicating that the heart is struggling to pump blood effectively.

Structure of Atrial Natriuretic Factor

Atrial natriuretic factor is a type of peptide hormone that is produced and secreted by the heart. The structure of ANF consists of a linear chain of amino acids, which is folded into a specific 3-dimensional shape. ANF is synthesized as a large precursor molecule, called pro-ANF, which is then cleaved into its active form by proteolytic enzymes. ANF is secreted into the bloodstream by the heart and acts on specific receptors in the kidneys and blood vessels to produce its effects. The specific 3-dimensional structure of ANF is important for its biological activity, as it allows the hormone to bind to and activate its receptors.

Atrial Natriuretic Factor Production

Atrial natriuretic factor (ANF) is produced by the heart in response to increased pressure within the heart or increased blood volume. ANF is produced and stored in specialized cells in the atria (the upper chambers) of the heart, called atrial myocytes. When pressure or volume within the heart increases, ANF is synthesized and secreted into the bloodstream.

The production of ANF is regulated by a complex interplay of hormones and signaling pathways, which includes renin-angiotensin-aldosterone , the sympathetic nervous system, and other factors. ANF production is increased in conditions such as heart failure, where the heart is struggling to pump blood effectively, and decreased in conditions such as dehydration, where blood volume is low.

Physiological effects of ANF

Atrial natriuretic factor has several important physiological effects:

1. Natriuresis: ANF acts on the kidneys to increase the excretion of salt (sodium) and water, which reduces blood volume and blood pressure.
2. Vasodilation: ANF acts on blood vessels to cause them to relax and dilate, which further reduces blood pressure.
3. Suppression of the renin-angiotensin-aldosterone system: ANF suppresses the production and action of the renin-angiotensin-aldosterone system, a hormone system that regulates blood pressure and fluid balance.
4. Suppression of the sympathetic nervous system: ANF suppresses the activity of the sympathetic nervous system,  thus regulating blood pressure.

Therapeutic and clinical significance of Atrial Natriuretic Factor

Atrial natriuretic factor (ANF) has both therapeutic and clinical significance due to its ability to regulate blood pressure and fluid balance.

1. Therapeutic potential: ANF and its analogs have been studied as potential therapies for a variety of conditions, including heart failure, hypertension, and kidney disease. ANF therapy aims to mimic the physiological effects of the hormone and improve heart function, blood pressure, and fluid balance.
2. Clinical significance: Elevated levels of ANF in the blood are associated with heart failure, where the heart is struggling to pump blood effectively. ANF levels can be measured as a diagnostic tool for the heart failure and monitor response to treatment. ANF levels are also increased in conditions such as dehydration, where blood volume is low, and reduced in conditions such as liver cirrhosis, where fluid balance is disrupted.

Summary

When the heart experiences increased pressure or blood volume, ANF is generated in the atria of the heart. When ANF is released into the bloodstream, it influences the kidneys to enhance sodium and water excretion, which lowers blood volume and blood pressure. ANF is produced in the bloodstream by the heart and exerts its effects by interacting with certain receptors in the kidneys and blood arteries. When the heart struggles to pump blood efficiently, such as in heart failure, ANF production rises; when blood volume is low, such as in dehydration, ANF production falls. ANF’s physiological effects The hormone atrial natriuretic factor, which is produced by the heart, has several significant physiological consequences.

Frequently Asked Questions 

1. How does ANP prevent fibrosis?

ANP is thought to prevent fibrosis by several mechanisms:

1. Inhibition of fibroblast activation: ANP has been shown to inhibit the activation and proliferation of fibroblasts, the cells that produce and deposit the fibrous scar tissue in fibrosis.
2. Promotion of apoptosis: ANP has been shown to promote the apoptosis (programmed cell death) of fibroblasts, reducing the number of cells available to contribute to fibrosis.
3. Inhibition of oxidative stress: ANP has been shown to inhibit oxidative stress, a key contributor to fibrosis, by reducing the production of reactive oxygen species and promoting antioxidant defense mechanisms.

2. How does the atrial natriuretic factor is triggered?

The main mechanisms by which ANF is triggered  are:

1. ANF is triggered by atrial volume receptors expanding the atrial wall.
2. ANF is activated by an increase in sodium content.

3. What is the role of ANP in heart failure?

It regulates fluid balance and blood pressure in the body and has been shown to provide therapeutic advantages in heart failure patients. ANP levels are frequently raised in patients with heart failure as a result of the increased workload and pressure on the heart.

Introduction

• The chemical bond formation was first interpreted by the Lewis approach. However, the origin of covalent bonds and the nature of the attraction force between neighbouring atoms in molecules remain unexplained.
• As a solution, German scientists Fritz Wolfgang London and Walter Heinrich Heitler developed the valence bond hypothesis. Schrodinger’s wave equation was used to characterise the formation of a covalent bond between two hydrogen atoms by electron sharing.
• The principles of electronic configuration, electrical structure and atomic orbitals (and their overlap), and the hybridisation of most atomic orbitals are the main topics of this theory. Atomic orbitals that overlap and the electrons that are concentrated in the matching bond area create chemical bonds. 

What is Valence Bond Theory?

The valence bond theory describes the electrical structure of atoms and molecules. The concept explains how electrons are distributed among a molecule’s atomic orbitals. To better understand chemical bonding, the VBT incorporates quantum mechanical principles and explains the electrical makeup of molecules.

According to this theory, all the potential energy levels of an atom in a molecule are occupied, and all bonds are localized, atomic-scale bonds between two atoms that involve sharing an electron by both atoms. Because each atom has only one unpaired electron, their orbitals are weakly connected.

The two atomic orbitals don’t need to be the same. There can be interactions between, say, s and p orbitals. A sigma bond is formed when the orbitals of the two shared electrons intersect. However, Pi bonds are formed when the orbitals cross but remain perpendicular to one another. Since these atomic orbitals will overlap, the possibility of an electron existing in the bond position is highest. Because of the overlapping, electrons are most likely in the bond region.

Postulates of Valence Bond Theory

The main postulates of the Valence Bond Theory are outlined below:

• When two or more atoms come together, their unfilled outer electron shells overlap, creating a covalent bond.
• The orbitals of atoms must be sufficiently near together and properly oriented for overlap to occur.
• The only way for atoms to bind is through sharing electrons, which occurs when their valence orbitals overlap.
• There is an electron pair in overlapping orbitals, and their spins are antiparallel to one another.
• How tightly the orbitals overlap directly affects the quality of the established bond. Stronger covalent bonds are created when more atomic orbitals overlap. 
• When atoms combine to form a molecule, the resulting structure is identical to the original atoms.

Need for Valence Bond Theory

Combining the ideas of Lewis’s pair bonding with the Heitler-London theory, Linus Pauling proposed the valence bond theory in 1928. The concept of the valence bond was developed to account for resonance and orbital hybridisation.

Written by Pauling and published in 1931, “On the Nature of the Chemical Bond” is an in-depth analysis of valence bonds.

Lewis provides the systems to explain how molecules are arranged. However, it omitted to discuss the formation of chemical bonds. Similarly to that, the VSEPR hypothesis defines how essential molecules seem. However, its scope of use was relatively constrained. Additionally, the geometry of a complex atom was not described. To address and resolve these restrictions, scientists had to introduce the notion of valence bonding.

Modern Valence Bond Theory

• As an alternative to the valence bond idea, in which electron pairs are thought to be situated between a molecule’s two distinct atoms, covalent bonds can exist between atoms.
• Molecular orbital theory is the backbone of contemporary valence bond theory, which proposes that electron pairs are distributed around the molecule in sets of molecular orbitals.
• Predictions of magnetic and ionisation properties are simplified by molecular orbital theory, but valence bond theory provides greater nuance.
• The aromatic properties of molecules are attributed to the spin coupling between the pi orbitals, as proposed by contemporary valence bond theory.
• There is not much difference between the Dewar and Kekule arrangements from the perspective of the concept of resonance.
• According to molecular orbital theory, aromaticity is conceptualised as the delocalisation of the pi-electrons. According to molecular orbital theory, the ions participating in a chemical reaction are incorrectly predicted by the function representing the hydrogen molecule. In turn, this causes atoms to link together chemically.

Applications Of Valence Bond Theory

• VBT’s most significant use is in predicting molecular structure. VBT can be used to predict the shape and size of molecules by taking into account the distribution of electrons among atoms.
• The formation of chemical bonds can also be understood using VBT. VBT can explain the type of bond formed between two atoms by understanding the electron-sharing between the atoms. Predicting the strength of a bond and the reactivity of a molecule are two areas where this is particularly helpful.
• The physical and chemical properties of a molecule, like its melting and boiling points, can be predicted with this method.

Summary

The valence bond theory is a chemical bonding concept that describes the nature of the chemical bond between two atoms. Like molecular orbital (MO) theory, it employs quantum mechanical principles to describe bonding. According to the valence bond theory, bonds are formed when unoccupied atomic orbitals overlap. To form a bond, the two atoms use the same unpaired electron to occupy an orbital, resulting in a hybrid orbital. Both sigma and pi bonds are accounted for in the valence bond theory.

Frequently Asked Questions

1. What are the limitations of the Valence Bond Theory?

Ans: Valence Bond Theory is limited in its ability to explain the behaviour of electrons in molecules that contain more than two atoms. It is also limited in its ability to explain the behaviour of electrons in molecules that contain multiple bonds.

2. How does the Molecular Orbital Theory vary from the Valence Bond Theory?

Ans. The Valence Bond Theory explains how atoms in a molecule share electrons to form chemical bonds. Molecular Orbital Theory is based on the idea that electrons in a molecule occupy discrete energy levels, or “orbitals,” around the nucleus.

3. To what extent does geometry factor into the theory of valence bonds? 

Ans. Quite simply said, valence bond theory relies heavily on geometric     considerations. How electron pairs are arranged around a molecule’s core atom determines the structure’s three-dimensional shape. Linear, trigonal planar, tetrahedral, and octahedral arrangements are all possible for the electron pairs. Chemical bond strength and reactivity are both affected by the shape of a molecule, which is determined by the arrangement of electron pairs.

Introduction

A mixture is formed by physical means constituting two or more types of components. A mixture is usually of two types: homogeneous and heterogeneous mixture. Heterogenous mixtures are non-uniform mixtures which do not have a single phase throughout.  The word “homogeneous” has roots in Latin and Greek. The words homo and gene mean “same” and “kind,” respectively. Hence, if a mixture is described as homogenous, all of the mixture’s components are the same. 

What are Homogeneous Mixtures?

Substances in a homogeneous mixture are uniformly distributed across the entire medium. To put it another way, a sample taken from any point within a homogeneous mixture will have the same composition and yield the same results.

If, for instance, a solid-liquid solution is divided in half along its volume, each half will have the same amount of liquid medium and dissolved solute. 

Some essential characteristics of a homogenous mixture are- 

• A pure substance is made primarily of one type of thing, such as sodium metal or hydrogen gas. Homogeneous mixtures and solutions are often referred to as pure materials since their constituent parts are difficult to identify. 
•  The constituents of a homogenous mixture can be split into their original entities through physical means such as evaporation, distillation, etc. 

Classification of homogeneous mixtures:

Homogenous mixtures are usually categorized based on their phase, as follows:

Liquid Homogenous mixture

A solution is a homogenous liquid mixture of two or more substances. When a solute needs to be dissolved, a solvent is used. One such example is water. A solute is primarily a component that is present in lesser quantity. An everyday example is sugar. For illustration, consider the mix of water, sugar, and flavour. 

Solid Homogenous mixture: 

A classic example of a solid homogenous mixture is an alloy. It is solid at room temperature and has the same composition throughout.  

Gaseous Homogenous mixture

A gaseous homogenous mixture has two or more two gases dispersed evenly. For example, the air is a gaseous homogenous mixture with various gases, such as oxygen, carbon dioxide, nitrogen, etc, distributed evenly in the entire space. 

Applications

Homogeneous mixtures have various uses and can be found in many commonplace objects, ranging from man-made polymers to naturally occurring solids like stone.

• Homogeneous mixtures find widespread use in the food business. Products like salad dressings, sauces, and soups are all examples of homogeneous combinations. All of these concoctions result from blending various substances in calculated proportions to get a specific taste or feel.
• The majority of drugs, including cough syrups and eye drops, are homogeneous mixtures. These concoctions are made by combining various active components in a calculated proportion.
• The manufacturing sector also makes use of homogenous mixes. Paints, adhesives, and lubricants are a few examples of products that use homogeneous mixes. To achieve the necessary uniformity or performance, these mixtures are made by combining several elements in a calculated proportion.
• Chemical reactions and chromatography are just two examples of experiments that need uniform solutions. To provide the intended effect, various compounds are combined in a predetermined proportion to produce these mixes.

• Alloys of precious metals like gold, silver, and platinum are produced using homogeneous mixes in the jewellery industry. Many types of jewellery, from rings to necklaces, are crafted from these alloys. The uniform combination of metals results in an appearance and feel that can’t be replicated with just one metal. 
• Homogeneous mixes are utilised to produce lightweight and robust alloys for the aerospace sector. Materials from these alloys are used to fabricate parts for aeroplanes, such as landing gear and fuselage pieces. The alloy produced by the uniform combination of metals is robust and lightweight, making it a good candidate for aeroplane use.

Summary

A homogeneous mixture is a uniform mixture having a clear composition and recognizable characteristics. The components of a homogeneous mixture are invisible. An illustration of a homogeneous mixture is a salt solution dissolved in water. It is impossible to distinguish the salt from the water when it dissolves since it spreads completely throughout the water, producing the same component of the solution.

 

Frequently Asked Questions

1. What are the indications that a mixture is homogeneous?

Ans. Consider the sample size of a combination to determine its nature. It is heterogeneous if there are multiple phases of matter or distinct locations in the sample. The mixture is homogeneous if its composition seems uniform no matter where you examine it.

2. How can a homogenous mixture be separated?

Ans.  Homogenous mixtures cannot be separated by physical means, such as filtration or distillation.

3. Do solutions usually include homogeneous mixtures?

Ans. Although all homogeneous mixtures are solutions, not all solutions are homogeneous mixtures. A homogeneous mixture is a solution if there is only one phase present. When a solute is fully dissolved in a solvent, no undissolved particles remain as a result. 

Introduction

Various important materials in our daily life remain in a form of a mixture. So, for proper utilization of that element, we need to separate them. Depending on the nature of the materials, they are separated using a different procedure. There are different separation techniques like hand-picking, sieving, filtration, winnowing, and threshing, etc. In the winnowing process, heavy particles are separated from the lighter ones using blowing wind. In our daily life, the mixture of wheat and husk is separated by the winnowing process. 

Define the Winnowing process

• Heavy materials are separated from lighter substances using the wind. 
• The grains of rice and wheat are separated from their husks by this method.
• The mixture of grain and husk is taken in a sieve and shovel and put down from a height to the ground level. The force of wind causes the heavier grains to settle down to form a heap while the lighter husk elements are pushed aside.

The basic principle of the winnowing process

This process works based on the differences in mass between two substances that will be separated. Lighter particles are separated from heavy particles using this method. As the weight of heavy particles is higher than the lighter particles, they gather up on the surface in the shape of a heap. And the lighter particles are pushed away by the wind. 

Techniques used in winnowing 

• Winnowing separates rice or wheat grains from the chaff and husks using strong winds. Farmers would throw rice from a height and wait for several hours for the air to blow before separating the rice grains from the chaff with the help of shovels or sieves.
• The development of a winnowing machine coincided with the globalisation of industry. Today, farmers may pedal to alter the wind speed created by wind winnowing equipment. Farmers no longer need to depend on the wind to blow. They can winnow an unlimited amount of paddy or rice in a short amount of time. Farmers can utilize them even during the rainy season as the equipment can be operated inside of a sizable confined environment. We may purchase numerous winnowing machines on the market today.
• A winnowing fan, a special-shaped basket for shaking grains, harnesses the wind to separate lighter grain particles. Modern winnowing fans can be made of many different materials, such as paper, bamboo, or cane fans that can create wind from nothing.
• Using a device like a pitchfork, a winnowing fork also employs wind to separate grain chaff. When the grains from the fork are winnowed, the chaff is blown away and the grains that fell to the ground are gathered by the farmers.

Advantages of winnowing

• Winnowing is an essential part of farming production, particularly in paddy fields.
• Husks can be fed to cattle if they separate from grains.
• The machinery used for winnowing is simple to use.
• This method is inexpensive.
• There is no requirement for fuels because they generate wind using pedal power.
• The winnowing technique is an environmentally-friendly method.  
• It facilitates getting rid of husks that are indigestible to people.

Disadvantages of winnowing

• It does not apply to mixtures with heavy particles or mixtures in which all of the components are the same size. Winnowing is thus only appropriate for mixes in which one component is lighter compared to the other.
• For removing stone particles, winnowing is not appropriate.
• Substances that are heavier than grains cannot be winnowed.
• Lighter particles are removed during the winnowing process by blowing air across them. When there is no wind on a particular day, winnowing is challenging. This is the drawback of manual winnowing.

Summary 

The method of winnowing involves using the wind to separate light and heavy materials. The mass difference between heavy and light particles is the key factor in this process. Winnowing is a procedure that facilitates removing the husk from grains like rice or wheat. It can be employed to separate the husks from millet, wheat, rice, and corn. Substances that are denser than grains cannot be winnowed.

 

Frequently Asked Questions 

1. What is sieving? Where is it used?

Ans: Use of a sieve, a tool found in flour mills and construction sites, is required for the sieving process, which involves separating smaller particles from bigger particles. By applying sieving in the mill, small stones and husks can be removed from the flour. This technique can be used to separate sand from pebbles and stones.

2. Can we consume grains directly after winnowing? 

Ans: After winnowing, we cannot eat grains straight. Because winnowed grains may still contain small stones or other particles even after the husks have already been removed. So, it is best to hand-pick these stones out of the winnowed grains.

3. Why is threshing so important before winnowing? 

Ans: Threshing is the process used to separate grains from their surrounding husks and straw. After reaping, this treatment should be carried out before the winnowing procedure. Any delay after cutting and threshing allow the grains to quickly deteriorate while the harvest is drying in the field or when it is heaped in the fields.

Introduction

Wool is a kind of fibre that is an important component in every living being’s life. It is obtained from various animals using specific extraction techniques, and it is then used for a variety of applications. Wool is that substance that gives protection to us in chilling weather conditions. It is used irrespective of country or place or type of people. Different animals contribute to making this useful fibre for us. We use special machines and procedures to extract those raw fibres and process them for daily use.

What is wool made of?

Wool is an animal fibre that is mostly composed of protein with a small number of lipids. The hairs obtained from animals like sheep, goats, yaks, rabbits, and other animals are utilised in the fabric industry for the manufacturing of wool. This contains less cellulose than other plant fibre including cotton.

Steps of making wool from sheep

The two types of fibres that are present in sheep’s hair. Those are beard hair and skin hair. Skin hair is used to make the fibre for wool. In order to raise lambs with just soft underlayers to generate such soft and fine hair, varieties of sheep with only thin under hair were specially chosen. Selective breeding is the method of picking parents to develop offspring with distinct features, such as sheep with silky hair.

Various methods are involved in the extraction to making wool 

Shearing-

• This is the preliminary stage in the processing of fibre into wool.   
• The sheep’s fleece and a thin skin layer are removed using this method.
• This treatment is only performed during the spring since sheep don’t require their outer layer of skin to stay warm.
• Shearing is performed by machines and on occasion by human hands.

Scouring-

Big containers of water are used to clean the shaved hair after the shearing process to remove oil, dust, and other impurities. Cleaning freshly shorn hair is referred to as scouring.

Sorting-

During sorting, hairs of different textures and types are separated. After this one can distinguish between low and high-quality fibres. The lower-grade fibres are used to make carpets, while the better-quality fibres are used to make garments. The fleece is sorted as per type and texture.

Dyeing-

This process includes colouring the fibres as natural fibre is usually white, black, or brown.

Rolling, combing, and straightening-

Following the colouring process, the recovered fibres are combed, rolled, and straightened into skeins.

Yaks, goats, lamb, and rabbits are just a few of the various species that can be used as the primary source of wool. These animals’ skin hairs are made up of two different types of fibres, which when combined create their fleece: 

1. The unruly and coarse hair.
2. The soft, fine, hair that is near the skin.

Other sources of wool 

• Yak: The use of yak wool is widespread in Tibet and Ladakh. They are well known for having long fur.
• Angora goats: Mountainous regions like Jammu and Kashmir are home to many angora goats. The fibre from Angora goats is angora wool, also referred to as mohair. A distinct breed of goat famous for its soft, silky under hairs is the cashmere goat. They are therefore used to weave shawls. These shawls are frequently referred to as “Pashmina shawls” in India.
• Camels: Camel’s body hair can be used to create many types of wool. Bactrian camels produce the best-quality wool. Alpacas and llamas from South America also produce wool.
• Angora rabbits: Angora wool is also known to be produced by angora rabbits and is soft, silky, and is sold at very high rates. 

Properties of wool 

Elastic- Natural flexibility of wool makes it feasible for garments to expand to accommodate your body while keeping their original shape. As a result, it is advised to exercise in fine wool clothing.

Odour resistant- Compared to synthetic textiles, wool is better at absorbing moisture vapour, which allows less perspiration to gather on your body. Merino even absorbs and locks away the smells from perspiration that are later released upon washing.

Soft- Wool fibres are soft because they can stretch significantly more than more typical, bigger wool fibres since they are so thin. Wool has a delicate, silky sensation next to your skin.

Breathable- Wool fibres can move a lot of moisture away from the skin so that it can dissipate into the atmosphere, making them breathable. 

Warm and cool- Unlike synthetic fabrics, wool is an active fibre that reacts to changes in the body’s heat, making it both warm and cool. As a result, it helps to keep you warm in the winter and cool in the summer.

Anti-wrinkle- Because each fibre is curled like a spring on a tiny level and springs back into position when bent, this material is anti-wrinkle. Because of this, wool apparel is naturally wrinkle-resistant

Summary

The body hairs (fleece) of animals such as sheep, goats, rabbits, llamas, alpacas, camels, bison, and yak are used to create wool, a type of animal fibre. The breeds of animals employed influence the grade of the wool on a worldwide scale. In order to stay warm and sheltered from the chilling weather, the most of animals that live on hilly slopes develop thick long hair surrounding their bodies. Animal fur holds a significant amount of air which is a poor conductor of heat. Thus, they continue to be heated.

In cold areas, woolen clothes keep us warm. Many different animal breeds can generate wool. The high-quality wool produced by the Merino, Rambouillet, Debouillet, and Lohi sheep breeds is well known. Angora and Cashmere goats produce the soft, wool-like Mohair and Pashmina, respectively.

Frequently Asked Questions 

1. Is wool a fire-resistant material? 

Ans: Wool has a higher level of fire resistance than other fibres since it is naturally flame resistant. Wool does not melt, leak, or adhere to the body when it burns, either.

2. What type of wool is the warmest?

Ans: Angora is the wool that provides the most heat. It is 2.5 times warmer than fur from sheep and is thick and fluffy. It also has the strongest moisture-wicking properties of any natural fibre.

3. Which disease is triggered by the wool industry?

Ans: Wool apparel is frequently associated with a synthetic sickness known as anthrax. It used to be a major worry, mainly for wool sorters, but because of industrial practices and changes in exporting countries where anthrax is an endemic disease, it is now almost fully regulated in the wool textile industry.

Introduction 

We need the purest form of metalloids like silicon, and germanium for the production of semiconductors. These metalloids behave like metals as well as non-metals whenever necessary. They are extensively used all over the world in all electronic gadgets and appliances. U.S. scientist W.G.P fann invented this technology in the 1950s with a motive to purify these elements to their best. This process is also known as zone melting or travelling melting zone.  

Define zone refining 

• It is an advanced technique that combines crystallization and melting processes to isolate the cleanest crystals from contaminated components, specifically metals. The crystal is heated just enough during this process to melt any impurities, which creates a covering of molten zones that moves along the crystal’s surfaces.
• It is often used to describe the process of purifying a crystal that involves melting a small portion of the crystal. The produced molten zone is moved over the crystal.
• Impurities mixed with metals get melted at the forward border. The process leaves behind remains of the pure element that has crystallized.

Principle of zone refining 

• This method of refining is based on the idea that impure substances are more soluble when they are molten. Every time a molten metal crystallizes during the cooling phase, impurities are quickly eliminated because they do not contribute to the composition of the pure crystals.
• By passing the liquid region through a rolling heater, contaminants are removed, and the resulting re-crystallized pure metals are left behind in the form of solid metal. The zone must travel as slowly as possible throughout this progressive process to produce a highly pure version of the metal.

The Process of zone refining

• On one end of the contaminated metal pole that needs to be refined in the zone purification process, a movable radiator is installed. A portable heater in the shape of a circle is used to secure the unrefined metal rods inside a space that is filled with inert gas.
• This round heater heats the pole uniformly, producing a zone where the temperature steadily rises to the melting point in a direction perpendicular to the center of the rod. As the heater moves throughout the pole, the melted zone slides down the rod.
• Gradually warming the radiator all the impurities along with the pure metals liquefy, but molten impurities get transferred with the liquid zone whereas purified metal recrystallizes.
• Toward the completion of the cycle, solid purified metal stays on one side while contaminants build on the other. This process is repeated numerous times to get the purest form of the metal.

Application of zone refining 

• To get the purest kind of metal, the zone refining process is typically used.
• Before creating an aqueous phase, this procedure is applied to concentrate biological components that are heat-labile.
• It is used to condense any enzyme, drug, protein, or other temperature-sensitive molecule during the crystallization process.
• Zone refining is a process used to make solar cells.
• It works remarkably well in cleaning impurities from semiconductors.
• Making organic compound benchmarks for High-Performance Column Chromatography, Fluorescence Spectroscopy, or even Spectrophotometry is a breeze with it.
• This process is very helpful for all analytical procedures that require the highest degree of purity for standardization or equipment calibration.

Limitations of the zone refining process 

• Zone refining is a very costly procedure.
• Its applications are restricted to important synthetics and laboratory reagents.
• Zone refining must be utilized in conjunction with other processes in order to attain a sufficient level of purity.

Summary 

Zone refining is a process used to separate the finest crystals from impurities. In this process, melting and crystallization methods are used. It works well for getting highly pure metals. Other names for it include zone melting, zone floating, and travelling melting zone method. It is a very expensive method that occasionally requires the use of additional methods to remove impurities. With this technique, impurities in semiconductor materials like silicon, germanium, and gallium can be successfully eliminated.

 

Frequently Asked Questions

1. Describe Vapour-Phase Refining

Ans: In the vapor phase refining process, the metal element should generate a volatile complex whenever a reagent is present. The complex must rapidly dissolve for the metal to be recovered. This causes the metal volatile complex to form, and this is the resulting complex that is broken down to produce pure metal. Nickel and titanium are such examples.

2. What is the process of distillation in the Purification of Metals?

Ans: Metals having boiling points are the only ones that can be purified using this procedure. It happens whenever a metal is heated above its boiling point, causing vapors to form. Since the vapors only contain pure metal that has condensed, the impurities are set aside before the vapors are transferred to another storage facility. For example mercury, and zinc. 

3. What is the procedure involved in the electrolytic refining of metals? 

Ans: The contaminated metal should act as the anode in electrolysis, losing ions continuously, while the pure metal acts as the cathode, receiving ions across the whole process. The metal with the smallest basicity is transferred to the anode when an electric current flows through this electrolytic mixture, whereas the metal with the maximum basicity stays in the mixture. For instance, copper and aluminium.

Introduction

The valency of an element is indicated by its maximum capacity of making covalent bonds with any other element or the same element. Carbon has tetra valency since it can form a maximum of four bonds with another C atom or with other atoms like S, H, O, Cl, N, etc. Based on this, C atoms can form several organic compounds like Methane (\(C{H_4}\)), ethane(\({C_2}{H_6}\)), etc. Moreover, carbon can create compounds with both double and triple bonds among its atoms. Carbon chains can sometimes be ring-shaped, branched, or linear.

Define tetravalency of Carbon:

• Tetra signifies “four,” but “Valency” refers to “combining ability.” When carbon has a valency of four and can establish four covalent links with another atom, it is said to be tetravalent.
• The capability of carbon to form covalent linkages with the other carbon molecules tends to be referred to as catenation
• Due to the very small size of carbon, it can undergo catenation.

Reasons behind the tetravalency of Carbon:

The atomic number of carbon is 6 and its electronic configuration is \([He]2{s^2}2{p^2}\). The four electrons in the valence cells mean that the carbon atom can no longer lose or gain four electrons since doing so would require a significant amount of energy. Thus, the four electrons of carbon are shared with other elements. Since its electron has also been shared, there appear to be four shared electrons.

As a consequence, carbon’s valency becomes four, and as an outcome, “Carbon is Tetravalent.” Electrons can neither be generated nor taken up by carbon; it could only transfer them. Its tetravalent character influences the majority of the organic compounds.

Explanation of tetravalency by ground state and excited state configuration of carbon:

tetravalency at Ground state:

The lowest energy level is called the ground state. Most of the electrons in carbon’s ground state are at their lowest available energies. Despite having four electrons, carbon can only create two bonds because its ground state only has two unpaired electrons.

Excited state: 

Carbon is in an excited singlet state whenever the whole energy of the electrons may be lowered by first transferring one electron from the 2s orbital to the 2p orbital. In its excited state, carbon possesses four unpaired electrons, which allows it to form bonds with four other atoms.

For example, one 2s and three 2p electrons combine to form \(s{p^3}\) hybridization. Methane that is \(C{H_4}\) possesses \(s{p^3}\)  hybridization of the C atom. The structure of methane is tetrahedral where C is linked with four H atoms and forms covalent bonds.

The hybridization of carbon in different compounds:

• \(s{p^3}\) hybridization: C atom forms four covalent bonds with four H atoms in\(C{H_4}\). The hybridization of C in \(C{H_4}\) is \(s{p^3}\). \(C{H_4}\) has a tetrahedral structure.
• \(s{p^2}\) hybridization: In ethylene molecules, two C atoms are joined together by one sigma bond and one pi bond. The hybridization of C in \({C_2}{H_4}\) is \(s{p^2}\).
• sp hybridization: Two sigma bonds and two pi bonds are observed in the structure of \({C_2}{H_2}\) (acetylene). Since carbon typically forms two sigma bonds, two of its valence orbitals can combine to generate two orbitals that seem to be equivalent to one another.

Summary 

We may simply conclude that carbon tends to have the closest noble gas configuration since it couples its four valence electrons with several other elements and forms four separate covalent bonds. Tetravalency is the terminology used for this. In a later experiment, carbon proves that it has tetravalency across all hydrocarbons. The following features of carbon can make it the most flexible element in the periodic table: catenation, tetravalency, and isomerism. The production of such a large number of combinations from carbon compounds can be credited to each of these packages. Because they do not form bonds, inorganic composites have a lower number than organic composites.

 

Frequently Asked Questions

1. What other element other than carbon has tetravalency?

Ans: Si also can form four covalent bonds with other elements. That is Si is also tetravalent. But due to the larger size of Si as compared to C, Si doesn’t participate in catenation. Also, Si can’t form various compounds as C atoms can.

2. Is tetravalency possible for all semiconductors?

Ans: There is only one kind of element in it. The most abundant intrinsic semiconductor elements are silicon (Si) and germanium (Ge). Four valence electrons make them tetravalent. At the temperature of absolute zero, a covalent bond connects them to the atom.

3. Why is carbon considered to be a weak conductor of electricity?

Ans: Carbon compounds are found to contain covalent bonds. Covalent molecules do not disintegrate into ions in the aqueous phase;  hence they do not possess any free electrons. Even though there would be no charge transfer, this becomes a poor conductor of electricity.