Solved Objective Problems: Chemical Equilibrium | Chemistry Class 11 - NEET PDF Download

Problem 1 : The enthalpies of two reactions are DH₁ and DH₂ both positive with DH₂ > DH₁ . If the temperature of reacting system is increased from T₁ to T₂ predict which of the follow ing alternative is correct ?

(A) 
  (B)  
 (C)  
 (D) 
 

Ans. D Solution: As the temperature of reacting system is increased the equilibrium constant of reaction is also increased for endothermic reactions so for two reactions on increasing the temperature by equal amounts.

Problem 2: At a certain teperature 2 moles of crbonmonoxide and 3 moles of chlo rine were allowed to reach equilibrium according to the reaction CO Cl₂ COCl₂ in a 5 lit vessel. A t equilibrium if one mole of CO is present then equilibrium constant for the reaction is :

(A) 2 (B) 2. 5 (C) 3.0 (D) 4

Ans. B Solution: CO + Cl₂ COCl₂

At t = 0 2 3 0

At equilbrium (2-1 ) (3-1 ) 1

Concentrations   

Problem 3 : The numerical value of the equilibrium constant or any chemical change is affected by changing the

(A) concentration of product (B) catalyst

(C) concentration of reacting substance (D) temperature

Ans. D Solution : The equilibrium constant is unaffected by changing the concentration of products, catalyst and conentration of reactants. It is affected by changing the temperature.

Problem 4: The reaction : 3O₂ 2O3, DH= 69 , 000 calories is aided by :

(A) high temperature and low pressure (B) high temperature and high pressure

(C) low temperature and high pressure (D) low temperature and low pressure

Ans. B Solution : According to Le Chatalier principle formation of ozone is favoured by high temperature (endothermic reaction ) and high pressure.

Problem5 : In the homogenous reaction 2X₂  + 2Y₂  2X₂Y₂, DH is negative for forward direction.The mass of X₂Y₂ increased at equilibrium by

(A) Raising the temperature (B) employing a suitable catalyst

(C) reducing the total pressure (D) raising the total pressure

Ans. D Solution: If the temperature is decreased and pressure is increased then reactions proceeds in for ward reaction.

Problem6: The equilibrium constant at 323^oC is 1000. What would be its value in the presence of a catalyst in the forward reaction. 

A + B   C +  D 38 kcal

(A) 1000 x concentration of catalyst (B) 1000

(C)  (D) impossible to tell

Ans. B  Solution: The equilibrium constant vary only with temperature. At constant temperature it will not vary.

Problem 7 : K_p for the reaction : CO₂(g) + H₂(g)  CO(g) + H₂O(g) is found to be 160 at a given temperature. Originally equal number of moles of H₂ and CO₂ were placed in the flask . At equilibrium, the pressure of H₂ is 1.20 atm. What is the partial pressure of CO and H₂O?

(A) 4.80 atm each (B) 9.60 atm each

(C) 2.40 atm each (D) 1.20 atm each

Ans. A Solution: CO₂  +H₂  CO + H₂O

Problem 8: Kc for the reaction : N₂(g)+ O₂(g)  2NO(g) is 4.0 x 10^-6 at 400 K.Kp for the above reaction is

(A) 2.4 x 10^-3
 (B) 4.0 x 10^-6

(C) 4 x 10^-6 x (RT)2²
 (D) None of these

Ans. B Solution: N ₂  O₂ 2NO

for this reaction 

Since 

Problem-9: Which one of the following reactions at equlibrium , with all reactans and products in the gaseous phase, would be uneffected by an increase in pressure.

(A) N₂  +3H₂ 2NH₃ 
 (B) 2CO+ O₂  2CO₂

(C) 2H₂ + O₂ 2H₂O
 (D) N₂ + O₂  2NO

Ans. D Solution: N₂  O₂  2NO, the number of molecules of reactants and products are the same so it is not affected by the pressure.

Problem 10: For the gas phase reaction 2NO(g)  N₂(g) O₂(g) , DH = -43.5 kcal,which one of the following is true for N₂(g) O₂ (g) 2NO(g)

(A) K is independent of T
 (B) K decreases as T decreases

(C) k increases as T decreases
 (D) K varies with addition of NO

Ans. B

Solution: The given reaction N₂(g) O₂(g) 2NO(g) is endothermic.Therefore, according to  Le-Chaltlier's Principle , high temperature favours forward reaction and hence K ncrease as T increase or K decrease as T decreases.