Chemical Equilibrium MCQs 2026

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) ✓

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 ✓