Chemical Equilibrium MCQs 2026

Chemical equilibrium is reached when

1. A The reaction has completely stopped ✓
2. B All reactants are converted to products ✓
3. C The rate of the forward reaction equals the rate of the reverse reaction ✓
4. D Only products remain in the system ✓

Chemical equilibrium is described as

1. A Static ✓
2. B Dynamic ✓
3. C Irreversible ✓
4. D Permanent ✓

The equilibrium constant, Kc, is expressed in terms of

1. A Rate constants only ✓
2. B Activation energies ✓
3. C Molar concentrations of products and reactants at equilibrium ✓
4. D Pressure of reactants only ✓

A large value of the equilibrium constant (K >> 1) indicates that at equilibrium

1. A Reactants are favored ✓
2. B The reaction has not started ✓
3. C Reactants and products are equal ✓
4. D Products are favored ✓

A small value of the equilibrium constant (K << 1) indicates that at equilibrium

1. A Products are favored ✓
2. B Reactants are favored ✓
3. C The reaction is at completion ✓
4. D Equilibrium is not reached ✓

Le Chatelier's principle states that if a system at equilibrium is disturbed, the system will shift to

1. A Stop the reaction completely ✓
2. B Increase disorder indefinitely ✓
3. C Favor the reactants always ✓
4. D Counteract the disturbance and restore equilibrium ✓

According to Le Chatelier's principle, increasing the pressure on a gaseous equilibrium favors the side with

1. A More gas moles always ✓
2. B Equal moles on both sides ✓
3. C Fewer gas moles ✓
4. D No gas molecules involved ✓

For an exothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. A Products ✓
2. B Reactants ✓
3. C Neither side ✓
4. D Depends only on pressure ✓

For an endothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. A Products ✓
2. B Reactants ✓
3. C Neither side ✓
4. D Catalyst side ✓

Le Chatelier's principle states that if a system at equilibrium is disturbed, the system will shift to

1. A Stop the reaction completely ✓
2. B Increase disorder indefinitely ✓
3. C Favor the reactants always ✓
4. D Counteract the disturbance and restore equilibrium ✓

According to Le Chatelier's principle, increasing the pressure on a gaseous equilibrium favors the side with

1. A More gas moles always ✓
2. B Equal moles on both sides ✓
3. C Fewer gas moles ✓
4. D No gas molecules involved ✓

For an exothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. A Products ✓
2. B Reactants ✓
3. C Neither side ✓
4. D Depends only on pressure ✓

For an endothermic reaction at equilibrium, increasing the temperature shifts equilibrium towards the

1. A Products ✓
2. B Reactants ✓
3. C Neither side ✓
4. D Catalyst side ✓

Adding a catalyst to a reaction at equilibrium

1. A Shifts equilibrium towards products ✓
2. B Shifts equilibrium towards reactants ✓
3. C Speeds up attainment of equilibrium without shifting its position ✓
4. D Changes the value of Kc ✓

The equilibrium constant Kp is related to Kc by the equation

1. A Kp = Kc always ✓
2. B Kp = Kc / RT ✓
3. C Kp = Kc(RT)^Δn ✓
4. D Kp = Kc + Δn ✓

In the Haber process (N2 + 3H2 ⇌ 2NH3), increasing pressure favors the formation of

1. A N2 and H2 ✓
2. B NH3 (fewer moles of gas) ✓
3. C No change ✓
4. D Equal amounts of all species ✓

The equilibrium constant of a reaction depends on

1. A Temperature only ✓
2. B Concentration of reactants ✓
3. C Pressure only ✓
4. D Presence of a catalyst ✓

For a reaction at equilibrium, the reaction quotient Q equals K when

1. A The system is at equilibrium ✓
2. B The reaction has not started ✓
3. C Only products are present ✓
4. D The temperature changes ✓

If Q < K for a reaction, the reaction will proceed in the

1. A Reverse direction ✓
2. B Forward direction to reach equilibrium ✓
3. C No direction; it is already at equilibrium ✓
4. D Direction that decreases products only ✓

If Q > K for a reaction, the reaction will proceed in the

1. A Forward direction ✓
2. B Neither direction ✓
3. C Direction of increasing volume ✓
4. D Reverse direction to reach equilibrium ✓

Which type of equilibrium involves reactants and products in different physical states

1. A Homogeneous equilibrium ✓
2. B Static equilibrium ✓
3. C Heterogeneous equilibrium ✓
4. D Dynamic imbalance ✓

In a homogeneous equilibrium, all reactants and products are in the

1. A Same physical state/phase ✓
2. B Different physical states ✓
3. C Solid state only ✓
4. D Gaseous state only, never liquid ✓

The equilibrium expression for a heterogeneous reaction does NOT include the concentration of

1. A Pure solids and liquids ✓
2. B Gases ✓
3. C Aqueous ions ✓
4. D All species equally ✓

Which factor does NOT shift the position of a chemical equilibrium

1. A Presence of a catalyst ✓
2. B Change in concentration ✓
3. C Change in temperature ✓
4. D Change in pressure (for gaseous systems) ✓

The solubility product (Ksp) is an equilibrium constant that applies to

1. A Gaseous reactions only ✓
2. B Acid-base neutralization ✓
3. C Redox reactions only ✓
4. D The dissolution of a sparingly soluble ionic compound ✓

If the ionic product of a salt solution exceeds its Ksp, the solution is

1. A Unsaturated ✓
2. B Diluted ✓
3. C At equilibrium exactly ✓
4. D Supersaturated, and precipitation occurs ✓

The common ion effect refers to the decrease in solubility of a salt when

1. A Temperature is increased ✓
2. B A common ion is added from another source ✓
3. C The solution is diluted ✓
4. D A catalyst is added ✓

Dynamic equilibrium means that at the macroscopic level properties remain constant while at the molecular level

1. A All reactions have stopped ✓
2. B Only forward reaction continues ✓
3. C Only reverse reaction continues ✓
4. D Forward and reverse reactions continue at equal rates ✓

Which of the following statements about K (equilibrium constant) is true

1. A K changes when concentration changes ✓
2. B K changes with a catalyst ✓
3. C K is constant at a given temperature ✓
4. D K is always greater than 1 ✓

For the reaction A ⇌ B, if K = 1, at equilibrium

1. A [A] = [B] ✓
2. B [A] >> [B] ✓
3. C [B] = 0 ✓
4. D [A] = 0 ✓

Removing a product from an equilibrium mixture will shift the equilibrium towards

1. A The reactants ✓
2. B No change ✓
3. C The products (to replace what was removed) ✓
4. D A new catalyst-based state ✓

Adding more reactant to a system at equilibrium shifts the reaction towards

1. A The reactants ✓
2. B The products ✓
3. C No change ✓
4. D Equilibrium is destroyed permanently ✓

Which of the following is an example of a reversible reaction commonly cited in equilibrium studies

1. A N2 + 3H2 ⇌ 2NH3 (Haber process) ✓
2. B Combustion of magnesium ✓
3. C Neutralization of a strong acid with a strong base ✓
4. D Precipitation of AgCl (considered irreversible in these contexts) ✓

The contact process for manufacturing sulfuric acid involves the equilibrium

1. A N2 + 3H2 ⇌ 2NH3 ✓
2. B 2SO2 + O2 ⇌ 2SO3 ✓
3. C CaCO3 ⇌ CaO + CO2 ✓
4. D H2 + I2 ⇌ 2HI ✓

Increasing pressure has no effect on gaseous equilibria where

1. A Reactant moles exceed product moles ✓
2. B Product moles exceed reactant moles ✓
3. C The reaction is exothermic ✓
4. D The number of gas moles is equal on both sides ✓

The degree of dissociation of a weak electrolyte at equilibrium is affected by

1. A Nothing at all ✓
2. B Only the container's shape ✓
3. C Catalysts only ✓
4. D Dilution (per Ostwald's dilution law) ✓

Ostwald's dilution law relates the degree of dissociation of a weak electrolyte to its

1. A Molar mass ✓
2. B Concentration (dilution) ✓
3. C Color ✓
4. D Boiling point ✓

Which of the following equilibria is heterogeneous

1. A N2(g) + 3H2(g) ⇌ 2NH3(g) ✓
2. B H2(g) + I2(g) ⇌ 2HI(g) ✓
3. C 2SO2(g) + O2(g) ⇌ 2SO3(g) ✓
4. D CaCO3(s) ⇌ CaO(s) + CO2(g) ✓

For an equilibrium at constant temperature, changing the volume of the container affects

1. A K only, not the position ✓
2. B Nothing at all ✓
3. C Only solid-state equilibria ✓
4. D The position of equilibrium, but not K, for gaseous reactions with unequal moles ✓

The equilibrium constant expression is written using the

1. A Coefficients of reactants only ✓
2. B Rate law of the reaction ✓
3. C Activation energy ✓
4. D Balanced chemical equation's stoichiometric coefficients as exponents ✓

Which condition favors maximum yield of ammonia in the Haber process according to Le Chatelier's principle

1. A Low pressure and high temperature ✓
2. B High pressure and moderately low temperature ✓
3. C Low pressure and low temperature ✓
4. D High temperature and low pressure only ✓

In practice, industrial processes like the Haber process use a compromise temperature to balance

1. A Yield (favored by low T) and reaction rate (favored by high T) ✓
2. B Cost of catalyst and volume of reactor ✓
3. C Color of product and purity ✓
4. D Pressure and humidity only ✓

Which statement about reversible reactions is correct

1. A They can proceed in both forward and backward directions ✓
2. B They go to completion in one direction only ✓
3. C They never reach equilibrium ✓
4. D They require a catalyst to be reversible ✓

The equilibrium position of a weak acid dissociation in water is described by its

1. A Acid dissociation constant, Ka ✓
2. B Solubility product, Ksp ✓
3. C Rate constant, k ✓
4. D Molar mass ✓

A high value of Ka for an acid indicates that the acid is

1. A Weak ✓
2. B Strong (highly dissociated) ✓
3. C Neutral ✓
4. D Not soluble in water ✓

The equilibrium constant for the reverse of a reaction is related to the equilibrium constant of the forward reaction (K) by

1. A Kreverse = K ✓
2. B Kreverse = -K ✓
3. C Kreverse = K^2 ✓
4. D Kreverse = 1/K ✓

If the equilibrium constant of reaction 1 is K1 and reaction 2 is K2, and reaction 3 is the sum of reactions 1 and 2, then K3 equals

1. A K1 + K2 ✓
2. B K1 × K2 ✓
3. C K1 − K2 ✓
4. D K1 / K2 ✓

In a saturated solution of a sparingly soluble salt, the equilibrium exists between the

1. A Gas and liquid phases only ✓
2. B Two different solutes ✓
3. C Undissolved solid and its dissolved ions ✓
4. D Solvent and container walls ✓

The value of the equilibrium constant for a reaction at a fixed temperature is independent of

1. A The initial concentrations of reactants and products ✓
2. B Temperature ✓
3. C The nature of the reaction ✓
4. D The stoichiometry of the reaction ✓

Which of the following would increase the rate of both forward and reverse reactions equally without shifting equilibrium

1. A Increasing reactant concentration ✓
2. B Removing product ✓
3. C Adding a catalyst ✓
4. D Increasing temperature ✓

Equilibrium involving a solid and its saturated solution, such as sugar dissolving in water, is an example of

1. A Chemical equilibrium only ✓
2. B Redox equilibrium ✓
3. C Physical equilibrium ✓
4. D Nuclear equilibrium ✓

For the equilibrium PCl5(g) ⇌ PCl3(g) + Cl2(g), decreasing the pressure will shift equilibrium towards

1. A The products (more moles of gas) ✓
2. B The reactants (fewer moles of gas) ✓
3. C No shift occurs ✓
4. D Only PCl5 remains ✓

Le Chatelier's principle can be applied to predict changes in equilibrium due to all of the following EXCEPT

1. A Concentration changes ✓
2. B Pressure/volume changes ✓
3. C Changes in the amount of catalyst used ✓
4. D Temperature changes ✓

At chemical equilibrium, the Gibbs free energy of the system is

1. A Maximum ✓
2. B At a minimum ✓
3. C Increasing continuously ✓
4. D Equal to enthalpy ✓