Test: Chemical Equilibrium (13 July) - JEE MCQ

Concept:

• The constant which defines the relationship between the molar concentration of the reactants and the rate of the chemical reaction is known as the rate constant.
• The rate constant of a reaction depends on the following factors :
• Nature of the reactants. 
• Temperature of the reaction. As the temperature increases, the velocity constant (rate constant) increases. 
• The conditions of the reactions like the presence of the catalyst, solvent, pH, etc. 
• It does not depend on the concentration of the reactants. But if one or more substances are in excess concentration, then the order of the reaction is independent of them. 

Explanation:

Equilibrium constant for this reaction

Equilibrium constant for this reaction

On squaring both side of equation (ii), we get

Conclusion:

Thus, the equilibrium constant for the reaction  at the same temperature is 1/8

During dissolution of a substance, the volume decreases. When pressure is increased, the reaction will proceed in the forward direction which will decrease the volume and nullify the effect of increased pressure.
During the dissolution of a substance, heat is absorbed. Hence, the forward reaction will be favored by high temperature as the effect of increased temperature will be nullified by the absorption of heat.
Hence, the solubility of a substance which dissolves with a decrease in volume and absorption of heat will be favored by high pressure and high temperature.

For the reaction PCl₅ ⇋ PCl₃ ​+ Cl₂, the forward reaction occurs with an increase in the number of moles from 1 to 2. Also, the reverse reaction occurs with a decrease in the number of moles from 2 to 1.
When inert gas is added at constant pressure, the equilibrium will shift in the direction in which there is an increase in the number of moles of gases.
Thus, the addition of inert gas at constant pressure will increase the dissociation of PCl₅.
Option B is correct.

Degree of dissociation depends on all the above factors
1. Nature of electrolyte:-  Weak or Strong
(incomplete  dissociation) or (Complete  dissociation)
2. As the temperature increases, the degree of dissociation increases. 
3. The nature of solvent polar or non-polar also affects degree dissociation.
Option D is correct.

The reaction for the formation of ammonia is N₂ ​+ 3H₂ ⇔ 2NH₃ ​+ 92.2 kJ. Thus the reaction is exothermic and the sign of  ΔH is negative, i.e ΔH = −92.2kJ.

The magnitude of the equilibrium constant is not affected by the changes in concentrations of reactants and products, pressure and volume. Thus, when the concentrations of hydrogen and iodine are increased, the value of the equilibrium constant remains the same.

When the temperature of an exothermic reaction is increased, the reaction will proceed in the backward direction, so as to absorb heat and nullify the effect of increasing temperature. 
This will decrease the value of the equilibrium constant K_c . In other words, the equilibrium will shift to left.
Hence, B is the correct option.

The equilibrum reaction is 2SO₂ ​(g) + O₂ (g)⇔ 2SO₃ (g). The number of moles decreases in the forward reaction from 3 to 2. Also the number of moles increases in the reverse reaction form 2 to 3. When the pressure is increased by decreasing the volume at constant temperature, the forward reaction will be favored as the forward reaction occurs with decrease in the number of moles.

When a catalyst is present, the equilibrium is achieved faster but its magnitude remains unaffected. Thus the value of the equilibrium constant in presence of a catalyst is same as in absence of catalyst.
This is because, the catalyst influence the rate of forward reaction and reverse reaction to same extent.

For the reaction, N₂ (g) + O₂ (g) ⇔ 2NO(g), the value of Δn is 2 − (1 + 1) = 0 . When there is no change in the number of moles of reactants and products, there is no effect on the equilibrium when pressure is changed.
In all other option, the number of mole of reactant and products are different, Hence, if pressure is changed the equilibrium will be affected.