In a closed system at equilibrium, if the concentration of $H_2$ is increased in the reaction $H_2(g) + I_2(g) \rightarrow 2HI(g)$, what will be the effect according to Le Chatelier's principle?

There will be no change in the equilibrium position.

The equilibrium constant $K_c$ will increase.

Consider the equilibrium $$CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)$$. What will be the effect on the equilibrium position if the pressure is increased by decreasing the volume of the container?

The equilibrium will shift to the left, consuming $CO_2$.

The equilibrium will shift to the right, producing more $CO_2$.

The equilibrium will shift to the left, consuming $CO_2$.

The equilibrium will not change.

In the reaction $$N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$$, which condition will favor the formation of ammonia according to Le Chatelier's principle?

Adding an inert gas at constant volume

For the reaction $$N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$$, which of the following statements is true regarding the effect of temperature on the equilibrium constant $K_c$?

$K_c$ decreases with an increase in temperature.

$K_c$ increases with an increase in temperature.

$K_c$ decreases with an increase in temperature.

$K_c$ remains constant regardless of temperature changes.

The effect of temperature on $K_c$ cannot be determined.

Considering the reaction $2NO_2(g) \rightarrow N_2O_4(g)$, which is exothermic, how will an increase in temperature affect the equilibrium constant $K_c$?

The equilibrium constant $K_c$ will decrease.

The equilibrium constant $K_c$ will increase.

The equilibrium constant $K_c$ will decrease.

The equilibrium constant $K_c$ will remain unchanged.

The reaction will become non-spontaneous.

In the reaction $$CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)$$, what happens if the pressure is increased by reducing the volume of the container?

There is no change in equilibrium.

The concentration of $CO_2$ decreases.

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Equilibrium

Action Plan Notes Questions Mock-Test

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Buffer Solutions

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Ionisation Constants of Weak Acids and Weak Bases

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Ionisation of Water, Kw, pH and pOH

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Learning Objectives

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Learning Objectives

Understand the dynamic nature of chemical equilibrium and how it is established when the rate of the forward reaction equals the rate of the reverse reaction.
Apply the law of mass action to write equilibrium constant expressions for various chemical reactions.
Calculate equilibrium constants ( $K_c$ and $K_p$ ) and understand their dependence on stoichiometric coefficients.
Predict the effects of changes in concentration, pressure, and temperature on the position of equilibrium using Le Chatelier's Principle.
Analyze the temperature dependence of equilibrium constants and how it affects the direction of exothermic and endothermic reactions.
Explore heterogeneous equilibria involving multiple phases and understand the exclusion of pure solids and liquids in equilibrium constant expressions.
Use the reaction quotient ( $Q_c$ ) to predict the direction of reaction shifts to reach equilibrium.
Relate Gibbs free energy change ( $\Delta G$ ) to the equilibrium constant to determine reaction spontaneity.
Investigate equilibrium in physical processes, such as phase changes and solubility, including the application of Henry's law.
Utilize equilibrium constants to predict the extent of reactions, direction of reaction shifts, and calculate equilibrium concentrations from initial data.
Classify acids and bases using Arrhenius, Bronsted-Lowry, and Lewis concepts, and calculate ionization constants for weak acids and bases.
Explain the ionization of water, the ionic product ( $K_w$ ), and the relationship between $pH$ and $pOH$ .
Evaluate the strength of acids and bases using $pK_a$ and $pK_b$ values.
Understand the function and calculations related to buffer solutions and their resistance to $pH$ changes.

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Revision Notes & Summary

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Chapter Notes

Dynamic Chemical Equilibrium

Definition: A state where the rate of the forward reaction equals the rate of the reverse reaction, resulting in constant concentrations of reactants and products.
Dynamic Nature: At equilibrium, reactions continue to occur at the molecular level, but no net change is observed in the concentrations.
Law of Mass Action: The rate of a chemical reaction is proportional to the product of the masses of the reacting substances, each raised to a power equal to the coefficient in the balanced chemical equation.

Equilibrium Constant Expressions

Kc: Equilibrium constant in terms of concentration.
Kp: Equilibrium constant in terms of partial pressures.
Expression: For a reaction $aA + bB \rightleftharpoons cC + dD$ , the equilibrium constant is given by: $K_c = \frac{[C]^c[D]^d}{[A]^a[B]^b}$
Dependence on Stoichiometry: The powers in the expression are the stoichiometric coefficients from the balanced equation.

Le Chatelier's Principle

Principle: If a system at equilibrium is subjected to a change in concentration, pressure, or temperature, the system will adjust to counteract the effect of the change and a new equilibrium will be established.
Concentration: Adding a reactant or product shifts the equilibrium to consume the added substance.
Pressure: Increasing pressure shifts the equilibrium towards the side with fewer moles of gas.
Temperature: Increasing temperature favors the endothermic direction.

Temperature Dependence of Equilibrium

Exothermic Reactions: Increase in temperature decreases $K$ .
Endothermic Reactions: Increase in temperature increases $K$ .

Heterogeneous Equilibria

Definition: Equilibria involving more than one phase.
Expression: Pure solids and liquids do not appear in the equilibrium constant expression.

Reaction Quotient (Qc)

Definition: A ratio similar to the equilibrium constant but for non-equilibrium conditions.
Use: Predicts the direction of the reaction shift to reach equilibrium by comparing $Q_c$ with $K_c$ .

Gibbs Free Energy and Equilibrium

Relationship: $\Delta G = \Delta G^\circ + RT \ln Q$
Equilibrium: At equilibrium, $\Delta G = 0$ and $Q = K$ , so $\Delta G^\circ = -RT \ln K$ .

Equilibrium in Physical Processes

Examples: Solid-liquid, liquid-vapour, solid-vapour, solid-in-liquid, and gas-in-liquid equilibria.
Vapour Pressure: At equilibrium, the vapour pressure is constant.

Applications of Equilibrium Constant

Extent of Reaction: Large $K$ indicates products predominate; small $K$ indicates reactants predominate.
Direction: Compare $Q$ with $K$ to predict the direction of the reaction.
Equilibrium Concentrations: Calculate using initial concentrations and $K$ .

Acids and Bases: Arrhenius, Bronsted-Lowry and Lewis Concepts

Arrhenius: Acids produce $H^+$ in water, bases produce $OH^-$ .
Bronsted-Lowry: Acids are proton donors, bases are proton acceptors.
Lewis: Acids accept electron pairs, bases donate electron pairs.

Ionisation Constants of Weak Acids and Weak Bases

Ka and Kb: Measure the strength of weak acids and bases.
Ostwald's Dilution Law: Relates degree of ionization to concentration.

Ionisation of Water, Kw, pH and pOH

Kw: Ionic product of water, $Kw = [H^+][OH^-]$ .
pH and pOH: $pH + pOH = pKw$ .

pKa, pKb and Strength of Acids/Bases

Relation: $pKa = -\log Ka$ , $pKb = -\log Kb$ .
Strength: Lower $pKa$ or $pKb$ indicates stronger acid or base.

Buffer Solutions

Definition: Solutions that resist changes in pH upon addition of small amounts of acid or base.
Components: Typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid.

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Practice Test – MCQs, True/False

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Multiple Choice Questions

The equilibrium will shift to the right, favoring the formation of

N_2O_4

The equilibrium will shift to the left, favoring the formation of

NO_2

The equilibrium will remain unchanged.

The equilibrium constant will decrease.

Correct Answer: B

Solution:

Increasing the temperature favors the endothermic direction. Since the decomposition of

N_2O_4

into

NO_2

is endothermic, the equilibrium shifts to the left.

Chapter Concept:

Reaction Quotient (Qc)

The equilibrium will shift to the right, favoring the formation of

NH_3

The equilibrium will shift to the left, favoring the formation of

N_2

and

H_2

The equilibrium will remain unchanged.

The equilibrium constant will increase.

Correct Answer: A

Solution:

According to Le Chatelier's principle, increasing the pressure by decreasing the volume shifts the equilibrium towards the side with fewer moles of gas. In this case, the equilibrium shifts to the right, favoring the formation of

NH_3

which has fewer moles of gas.

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Equilibrium

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True or False

Correct Answer: True

Solution:

Dynamic equilibrium is characterized by equal rates of forward and reverse reactions, leading to constant concentrations of reactants and products.

Chapter Concept :

Dynamic Chemical Equilibrium

Correct Answer: True

Solution:

According to the principles of chemical equilibrium, for an exothermic reaction (where

\Delta H

is negative), the equilibrium constant

K

decreases as the temperature increases. This is because increasing the temperature shifts the equilibrium towards the reactants to absorb the excess heat, according to Le Chatelier's principle.

Chapter Concept :

Temperature Dependence of Equilibrium

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Equilibrium

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Buffer Solutions

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Ionisation Constants of Weak Acids and Weak Bases

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Ionisation of Water, Kw, pH and pOH

Learning Objectives

Learning Objectives

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Revision Notes & Summary

Chapter Notes

Dynamic Chemical Equilibrium

Equilibrium Constant Expressions

Le Chatelier's Principle

Temperature Dependence of Equilibrium

Heterogeneous Equilibria

Reaction Quotient (Qc)

Gibbs Free Energy and Equilibrium

Equilibrium in Physical Processes

Applications of Equilibrium Constant

Acids and Bases: Arrhenius, Bronsted-Lowry and Lewis Concepts

Ionisation Constants of Weak Acids and Weak Bases

Ionisation of Water, Kw, pH and pOH

pKa, pKb and Strength of Acids/Bases

Buffer Solutions

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Practice Test – MCQs, True/False

Multiple Choice Questions

Q1.For the reaction 2NO2(g)⇌N2O4(g)2NO_2(g) \rightleftharpoons N_2O_4(g)2NO2​(g)⇌N2​O4​(g), which of the following statements is true if the temperature is increased?

Correct Answer: B

Q2.According to Le Chatelier's principle, what will be the effect on the equilibrium position of the reaction N2(g)+3H2(g)→2NH3(g)N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)N2​(g)+3H2​(g)→2NH3​(g) if the pressure is increased by decreasing the volume of the container?

Correct Answer: A

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True or False

Q1.In a dynamic chemical equilibrium, the concentrations of reactants and products remain constant because the rates of the forward and reverse reactions are equal.

Correct Answer: True

Q2.In an exothermic reaction, the equilibrium constant KKK decreases with an increase in temperature.

Correct Answer: True

Q3.In a closed system, the equilibrium constant KcK_cKc​ for a reaction is independent of the initial concentrations of the reactants and products.

Correct Answer: True

High

pKa, pKb and Strength of Acids/Bases

High

Reaction Quotient (Qc)

High

Acids and Bases: Arrhenius, Bronsted-Lowry and Lewis Concepts

Medium

Heterogeneous Equilibria

Medium

Le Chatelier's Principle

Medium

Equilibrium Constant Expressions

Medium

Applications of Equilibrium Constant

Low

Dynamic Chemical Equilibrium

Low

Equilibrium in Physical Processes

Low

Gibbs Free Energy and Equilibrium

Low

Temperature Dependence of Equilibrium

Low

Q3.In a closed system at equilibrium, if the concentration of H2H_2H2​ is increased in the reaction H2(g)+I2(g)→2HI(g)H_2(g) + I_2(g) \rightarrow 2HI(g)H2​(g)+I2​(g)→2HI(g), what will be the effect according to Le Chatelier's principle?

Correct Answer: A

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Q4.Consider the equilibrium CaCO3(s)⇌CaO(s)+CO2(g)CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)CaCO3​(s)⇌CaO(s)+CO2​(g). What will be the effect on the equilibrium position if the pressure is increased by decreasing the volume of the container?

Correct Answer: B