7- EQUILIBRIUR

CHAPTER 10 EQUILIBRIUM

VERY QUESTIONS ANSWER

Q.1.What is meant by equilibrium?

Ans. Equilibrium is a state of balance or stability in a system where opposing forces or processes are in perfect balance, and there is no net change occurring.

Q.2.Define reversible process?

Ans. A reversible process is a thermodynamic process that can be undone without leaving any trace, as it occurs slowly and in perfect equilibrium at each step.

Q.3.Do reversible reactions go to completion?

Ans. No.

Q.4.What is physical equilibrium? give an example.

Ans. Physical equilibrium is a state where all forces acting on an object balance out, resulting in no net change in the object's motion; for example, a book resting on a flat table.

Q.5.Name three factors by which equilibrium state of reaction is disturbed.

Ans. Temperature change, pressure change, and concentration change.

Q.6. what is meant by which equilibrium is dynamic in nature”?

Ans. The phrase "equilibrium is dynamic in nature" means that the forward and reverse reactions continue to occur at the same rate, resulting in no net change in concentrations.

Q.7.Can equilibrium be achieved in open container if products can escape?

Ans. Yes.

Q.8.what are the conditions for getting maximum yield of so₃ by contact process?

Ans. The conditions for getting the maximum yield of SO3 in the contact process are using a low temperature, high pressure, and a suitable catalyst (vanadium pentoxide).

Q.9.Can a catalyst disturb the equilibrium in a reaction?

Ans. No, a catalyst does not disturb the equilibrium in a reaction.

Q.10.State the law of mass action?

Ans. The law of mass action states that the rate of a chemical reaction is directly proportional to the product of the concentrations of the reactants, each raised to the power of its stoichiometric coefficient.

Q.11.Define equilibrium constant and state law of chemical equilibrium?

Ans. Equilibrium constant: Numerical value representing the ratio of product concentrations to reactant concentrations at equilibrium.

Q.12.Stae Le-chatelier’s principle?

Ans. Le Chatelier's principle: When a system at equilibrium is subjected to an external stress, it will adjust itself to partially counteract the effect of the stress and restore a new equilibrium state.

Q.13.What is active mass?

Ans. Active mass: The concentration of a species in a reaction, usually expressed in terms of molarity (moles per liter).

Q.14.Under what condition a reversible process becomes irreversible?

Ans. A reversible process becomes irreversible when there is a large difference between the system's initial state and the surroundings, leading to significant irreversibilities and energy dissipation.

Q.15.Name the principle involved behind skating on ice?

Ans. The principle involved behind skating on ice is reducing friction through the formation of a thin layer of water from the pressure exerted by the skates, allowing for smooth gliding.

Q.16.At what temperature the solid and liquid are in equilibrium under I am pressure?

Ans. At melting point or freezing point?

Q.17.What does happen when pressure is applied on ice?

Ans. When pressure is applied to ice, it can melt and form a thin layer of water, reducing friction and allowing for easier movement.

Q.18.What does the value of equilibrium constant depend upon?

Ans. The value of the equilibrium constant depends on the specific chemical reaction and its stoichiometry at a given temperature.

Q.19.What is the thermodynamic criterion for the state of equilibrium?

Ans. The thermodynamic criterion for the state of equilibrium is that the Gibbs free energy change (ΔG) of the system is zero.

Q.20.What is the value of ΔG at equilibrium?

Ans. ΔG=0.

Q.21.What do you mean by ionic equilibrium?

Ans. Ionic equilibrium refers to the balance between the ionized and unionized forms of electrolytes in a solution.

Q.22.State Ostwald dilution law?

Ans. Ostwald dilution law: The square root of the ratio of the degree of dissociation to the initial concentration of a weak electrolyte is directly proportional to the dilution of the solution.

Q.23.Define electrolyte and non-electrolyte?

Ans. Electrolyte: A substance that produces ions when dissolved in a solvent, conducting electricity.

Non-electrolyte: A substance that does not produce ions when dissolved in a solvent, not conducting electricity.

Q.24.Define degree of dissociation?

Ans. Degree of dissociation: The fraction of molecules that dissociate into ions in a solution of a weak electrolyte.

Q.25.Define PH?

Ans. pH: A measure of the acidity or alkalinity of a solution, representing the negative logarithm of the hydrogen ion concentration.

Q.26.Name a substance which can act both as Bronsted acid as base?

Ans. Water (H2O) can act as both a Bronsted acid and a Bronsted base.

Q.27.What is meant by ionic product of water?

Ans. The ionic product of water is the product of the concentrations of hydrogen ions (H+) and hydroxide ions (OH-) in pure water at a given temperature, denoted as Kw.

Q.28.What do you mean by common ion effect?

Ans. Common ion effect refers to the suppression of the ionization of a weak electrolyte by the presence of a strong electrolyte containing a common ion.

Q.29.What is the PH of human blood?

Ans. The pH of human blood is approximately 7.4.

Q.30.What is POH?

Ans. pOH is the negative logarithm of the hydroxide ion concentration and is used to express the basicity of a solution.

Q.31.What is the limitation of PH scale?

Ans. The pH scale is limited to measuring the acidity or basicity of aqueous solutions and does not provide information about the strength or concentration of acids and bases.

Q.32.What is an indicator?

Ans. An indicator is a substance that changes color in response to changes in pH, used to determine the acidity or basicity of a solution.

Q.33.What do you mean by Degree of hydrolysis?

Ans. Degree of hydrolysis refers to the extent of a substance that has undergone hydrolysis, typically expressed as a percentage.

Q.34. Give limitations of Lewis concept?

Ans. Lewis concept does not explain the acid-base behavior in non-aqueous solvents and fails to predict the strengths of certain acids and bases accurately.

Q.35.What is PH scale?

Ans. The pH scale is a numerical scale used to specify the acidity or basicity of an aqueous solution, ranging from 0 (strongly acidic) to 14 (strongly basic), with 7 being neutral.

Q.36.Who introduced PH scale?

Ans. The concept of the pH scale was introduced by the Danish chemist Søren Peder Lauritz Sorensen in 1909.

Q.37.Define buffer solution give an example?

Ans. Buffer solution resists changes in pH upon addition of small amounts of acid or base; Example: Acetic acid-sodium acetate buffer.

Q.38.Give two characteristics of s buffer solution?

Ans. Two characteristics of a buffer solution: It maintains a nearly constant pH upon addition of small amounts of acid or base and contains a weak acid/base and its conjugate salt.

Q.39.What do you mean by solubility product?

Ans. Solubility product is the equilibrium constant for the dissolution of a sparingly soluble salt in water, representing the product of ion concentrations at saturation.

Q.40.What is buffer capacity?

Ans. Buffer capacity is the amount of acid or base that a buffer solution can neutralize while maintaining its pH within a certain range.

Q.41.What are acidic buffers?

Ans. Acidic buffers are buffer solutions with pH values less than 7, containing a weak acid and its conjugate base.

Q.42.What is basic buffer?

Ans. Basic buffers are buffer solutions with pH values greater than 7, containing a weak base and its conjugate acid.

Q.43.Name an important buffer in biology?

Ans. Hemoglobin is an important buffer in biology.

SHORT QUESTIONS ANSWER

Q.1.State and explain Henry‘s law?

Ans. Henry's law states that at a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid.

Explanation: When a gas is in contact with a liquid, some of its molecules will dissolve into the liquid phase until equilibrium is reached. The rate at which the gas dissolves is directly proportional to the partial pressure of the gas above the liquid. This means that if the partial pressure of the gas increases, more gas molecules will dissolve into the liquid, and if the partial pressure decreases, some of the dissolved gas will come out of the liquid and return to the gaseous phase. Henry's law is essential in understanding gas solubility in various applications, such as in the dissolution of gases in beverages, in gas exchange between blood and lungs, and in environmental processes like the absorption of gases in water bodies.

Q.2.Explain why can pure liquids and solids be ignored while writing the value of equilibrium?

Ans. Pure liquids and solids are usually ignored while writing the value of an equilibrium constant because their concentrations remain constant in a closed system, and they do not affect the equilibrium position.

In a chemical reaction involving pure liquids or solids, their concentrations are constant as long as the temperature and pressure remain constant. Therefore, their concentrations do not change during the course of the reaction, and they do not appear in the expression for the equilibrium constant.

For example, consider the reaction:

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⇌

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A(s)+B(g)⇌C(l)

The equilibrium expression for this reaction would be:

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]

[

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[B]

[C]

Since the concentration of the pure solid A does not change, it is not included in the equilibrium expression. Similarly, the concentration of the pure liquid C does not change, so it is also not included in the equilibrium expression.

Ignoring the pure liquids and solids in the equilibrium expression simplifies the expression and makes it easier to calculate the equilibrium constant based on the concentrations of only the reacting species, which can vary during the course of the reaction.

Q.3.What do you mean by homogeneous equilibria and heterogeneous equilibria?

Ans. Homogeneous equilibria occur when all the reactants and products in a chemical reaction are in the same phase (e.g., all gases, all liquids, or all aqueous solutions).

Heterogeneous equilibria, on the other hand, occur when the reactants and products are in different phases (e.g., a gas reacting with a solid, a liquid reacting with a gas, etc.).

Q.4.What is the law of chemical equilibrium?

Ans. The law of chemical equilibrium is also known as the law of mass action. It states that the rate of a chemical reaction at equilibrium is proportional to the product of the concentrations (or partial pressures) of the reactants, each raised to the power of their respective stoichiometric coefficients in the balanced chemical equation. This law is expressed by the equilibrium constant (Kc for concentrations and Kp for partial pressures). At equilibrium, the ratio of the concentrations (or partial pressures) of products to reactants remains constant, and this constant value is the equilibrium constant.

Q.5.What do you mean be Le-chateeller’s principle?

Ans. Le Chatelier's principle states that when a system at equilibrium is subjected to a change in temperature, pressure, or concentration of reactants or products, the system will shift its position of equilibrium to counteract that change and establish a new equilibrium. In other words, if a system is disturbed from its equilibrium state, it will respond in a way that tends to undo the disturbance and restore equilibrium. This principle helps predict how changes in conditions will affect the position of equilibrium in a chemical reaction.

Q.6.Why do sweets cause tooth decay?

Ans. Sweets cause tooth decay because the bacteria in our mouth feed on the sugars and produce acids as byproducts. These acids can erode the enamel, the protective outer layer of the teeth, leading to cavities or tooth decay. Regular consumption of sugary foods without proper oral hygiene can increase the risk of tooth decay and other dental issues.

Q.7.How does oxygen transport by haemoglobin in blood obeying Le-chatelier‘s principle?

Ans. The oxygen transport by hemoglobin in blood obeys Le Chatelier's principle through its ability to respond to changes in partial pressure of oxygen (pO2) in the surrounding environment.

When blood reaches the lungs, where the pO2 is relatively high, hemoglobin binds to oxygen to form oxyhemoglobin, according to the following reaction:

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Hb+4O2⇌Hb(O2)4

This reaction is favored in the lungs due to the high pO2, and hemoglobin readily binds to oxygen to form oxyhemoglobin.

Conversely, when blood reaches the body tissues, where the pO2 is relatively low (due to oxygen being used by cells), the equilibrium shifts to the left, and oxyhemoglobin releases oxygen to the tissues for cellular respiration:

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⇌

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Hb(O2)4⇌Hb+4O2

By shifting the equilibrium in response to changes in pO2, hemoglobin ensures that oxygen is efficiently delivered to tissues where it is needed and released in areas of low pO2. This behavior of hemoglobin follows Le Chatelier's principle, as it adjusts its equilibrium position in response to changes in the concentration of oxygen to maintain a balance in oxygen delivery throughout the body.

Q.8.What is Active mass?

Ans. Active mass, also known as the effective concentration, is the concentration of the species in a reaction that is directly involved in the chemical reaction. It is the concentration of the species that appears in the rate equation or the equilibrium constant expression.

In a chemical reaction, not all species present may be actively participating in the reaction. Only the reactants that collide with each other and successfully undergo a chemical change contribute to the rate of the reaction or affect the equilibrium position. Therefore, it is essential to consider the active or effective concentrations of the reacting species when analyzing reaction kinetics or equilibrium. Active mass is usually represented by square brackets ([ ]) in chemical equations to distinguish it from other concentrations that may not be directly involved in the reaction.

Q.9.What are electrolytes and non-electrolytes?

Ans. Electrolytes are substances that, when dissolved in water or other solvents, dissociate into ions and conduct electricity. They are capable of conducting electric current due to the presence of free ions in the solution. Examples of electrolytes include salts, acids, and bases.

Non-electrolytes, on the other hand, are substances that do not dissociate into ions when dissolved in water or other solvents. They do not conduct electricity because they do not produce free ions in the solution. Examples of non-electrolytes include most organic compounds like sugars, alcohols, and organic acids.

Q.10.Discuss different types of electrolytes?

Ans. Electrolytes can be categorized into three main types based on the nature of their ions when dissolved in water:

Strong Electrolytes: Strong electrolytes are substances that completely dissociate into ions when dissolved in water. They conduct electricity efficiently due to the high concentration of ions. Examples include strong acids (e.g., HCl, H2SO4, HNO3) and strong bases (e.g., NaOH, KOH).

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HCl (aq) →H

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→

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NaOH(aq)→Na

(Aq)+OH

−

(Aq)

Weak Electrolytes: Weak electrolytes are substances that only partially dissociate into ions when dissolved in water. They conduct electricity to a lesser extent than strong electrolytes due to a lower concentration of ions. Examples include weak acids (e.g., acetic acid, CH3COOH) and weak bases (e.g., NH4OH).

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COOH (aq) ⇌H

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COO

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(Aq)

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OH (aq) ⇌NH

(Aq)+OH

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(Aq)

Nonelectrolytes: Nonelectrolytes are substances that do not dissociate into ions when dissolved in water. They do not conduct electricity because there are no free ions present. Examples include most organic compounds such as sugars (e.g., glucose, sucrose), alcohols (e.g., ethanol), and urea.

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(Aq)

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OH(aq)

Understanding the different types of electrolytes is important in various applications, such as in determining the electrical conductivity of solutions and understanding the behavior of ionic substances in chemical reactions.

Q.11.Explain why an aqueous solution of a salt of weak base and strong acid is acidic in nature?

Ans. An aqueous solution of a salt of a weak base and a strong acid is acidic in nature due to the hydrolysis of the salt.

When a salt of a weak base and a strong acid dissolves in water, it dissociates into its constituent ions. The cation comes from the weak base, and the anion comes from the strong acid.

Let's take an example of ammonium chloride (NH4Cl) as the salt:

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−

Cl→NH

+Cl

−

The chloride ion (Cl^-) is derived from the strong acid (HCl), and it does not undergo any significant hydrolysis. However, the ammonium ion (NH4^+) is derived from the weak base ammonia (NH3), which can react with water:

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⇌

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O⇌NH

In this reaction, water acts as an acid, and it donates a proton (H+) to the ammonium ion, forming ammonia (NH3) and a hydronium ion (H3O^+).

Since the solution contains an excess of hydronium ions (H3O^+), it is acidic in nature. Thus, the overall acidity of the solution is due to the hydrolysis of the salt and the presence of hydronium ions from the weak base.

Q.12.What is the law of chemical equilibrium?

Ans. The law of chemical equilibrium, also known as the law of mass action, states that the rate of a chemical reaction at equilibrium is proportional to the product of the concentrations (or partial pressures) of the reactants, each raised to the power of their respective stoichiometric coefficients in the balanced chemical equation. It is represented by the equilibrium constant (Kc for concentrations or Kp for partial pressures) and expresses the relationship between the concentrations (or partial pressures) of products and reactants at equilibrium.

Q.13.What do you understand by chemical equilibrium? Give its four important characteristics?

Ans. Chemical equilibrium is a state in a reversible chemical reaction where the forward and reverse reactions occur at the same rate, resulting in a constant concentration of products and reactants over time.

Four important characteristics of chemical equilibrium are:

Constant Concentrations: At equilibrium, the concentrations of products and reactants remain constant. Although the forward and reverse reactions are still occurring, the rates are equal, leading to a balance between the amounts of reactants and products.

Dynamic Process: Chemical equilibrium is a dynamic process, meaning that the reactions have not stopped; rather, they are occurring at the same rate in both directions. The concentrations of reactants and products are stable, but the molecules continue to collide and interconvert.

Reversible Reaction: Equilibrium is achieved in reversible reactions, where reactants can form products and products can also react to form reactants. A double arrow (

⇌

⇌) is used to indicate a reversible reaction.

Independent of Initial Conditions: The position of equilibrium, determined by the equilibrium constant (

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), is independent of the initial concentrations or pressures of the reactants and products. As long as the temperature remains constant, any starting concentrations will eventually reach the same equilibrium concentrations. However, the time taken to reach equilibrium may vary depending on the initial conditions.

Understanding the characteristics of chemical equilibrium is essential in various applications, such as controlling reaction yields, designing chemical processes, and explaining the behavior of chemical systems in nature and industry.

Plus One

Thursday 4 February 2021

Unit 7 Equilibrium

Unit 7 Equilibrium

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