IIT – JEE 2014 TW TEST MARKS: 65

TIME: 1HR TOPICS:CHEMICAL EQUILIBRIUM

SECTION-I

This section contains 10multiple choice questions. Each question has 4 choices (A), (B), (C) and (D) for its answer, out which ONLY ONE is correct. (+3, - 1) 1. The graph below shows the variation of concentration with time for the reaction

3A(aq) B(aq) + 2C(aq) at 25oC.

What is the value of the equilibrium constant?

(a) 1.18 (b) 0.845 (c) 0.567 (d) 0.222

2. Consider the reaction: 2CO(g) + O2(g) 2CO2(g). If the equilibrium concentrations of CO(g) is 1.6

10-2 m/L, O2 is 9.0 10-2 m/L and CO2 is 6.4 10-2 m/L, what was the initial O2 concentration

before the reaction started to form any CO2(g)?

(a) 1.2 M (b) 12 M (c) 0.12 M (d) 0.012 M

3. Calculate the equilibrium concentration of H2 in a 1.0 L container initially containing 0.118 mole of

HBr at 1400 K. Kc = 1.5 10-5 at 1400 K for the reaction

2HBr(g) H2(g) + Br2(g)

(a) 1.8 10-6 M (b) 0.118 M (c) 1.5 10-5 M (d) 4.5 10-4 M

4. X, Y and Z react in the 1:1:1 stoichiometric ratio. The

concentration of X, Y and Z where found to vary with time as

shown in the figure below.

Which of the following equilibrium reacting may represent the

correct variation of concentration with time

(a) X(g) + Y(g) Z(g) (b) X(g) + Y(s) Z(g) (c)Z(g) + Y(g) X(g)

(d)Z(g) + X(g) Y(g) 5. The equilibrium constant for a reaction.

A B C D is 21.0 10 at 298 and is 2.0 at 373 K. The chemical process resulting in the formation of C and D is

(a) Exothermic (b) Endothermic (c) Unpredictable (d) None

2

X

Time (Minutes)

Conc.

(M

)

4

8

10

6

1 2 3 4 5 6

Y

Z

CAB

6. 1 mol of 2N is mixed with 3 mol of 2H in a litre container. If 50% of 2N is converted into ammonia

by thereaction 2 2 3N g 3H g 2NH g , then the number of moles of gas at the equilibrium are

(a) 1.5 (b) 4.5 (c) 3.0 (d) 6.0 7. Consider the reaction

A g B g C g D g

Which occurs in one step. The specific rate constant are 0.25 and 5000 for the forward and reverse reaction, respectively. The equilibrium constant is

(a) 42.0 10 (b) 24.0 10 (c) 55.0 10 (d) 62.5 10 8. For the equilibrium system

2 22HX g H g X g

the equilibrium constant is 51.0 10 . What is the concentration of HXif the equilibrium

concentration of 2H and 2X are 31.2 10 M, and 41.2 10 M respectively?

(a) 412 10 M (b) 312 10 M (c) 212 10 M (d) 112 10 M

9. 8 mol of gas 3AB are introduced into a 31.0dm vessel. It dissociates as 3 2 22AB g A g 3B g

At equilibrium , 2 mol of 2A is found to be present. The equilibrium constant for the reaction is

(a) 2 22mol L (b) 2 23mol L (c) 2 227mol L (d) 2 236mol L

10. What concentration of 2CO be in equilibrium with 0.025 M CO at o120 C reaction

2FeO s CO g Fe s CO g

If the value of cK 5.0 ?

(a) 0.125M (b) 0.0125M (c) 1.25M (d) 12.5M

SECTION-II This section contains 7 multiple choice questions. Each question has 4 choices (A), (B), (C) and (D) for its answer, out which ONE OR MORE is/are correct. (+3, 0) 11. Consider the following reversible systems

N2 + O2 1K 2NO;

2 2

1 1N O

2 2 2K NO

2NO 3K N2 + O2,

NO 4K 2 2

1 1N O

2 2

Correct relation between K1, K2, K3 and K4 is

(a) K1 K3 = 1 (b) 1 4K K 1 (c) 3 2K K 1 (d) none of these

12. The equation D d

(n 1)d

is correctly matched for : ( is the degree of dissociation, D and d are the

vapour densities before and after dissociation)

(a) n n

A B C2 3

(b)

n 2nA B C

3 3

(c)

n nA B C

2 4

(d)

nA B C

2

13. Variation of equilibrium constant K for the reaction

2A(s) + B(g) C(g) + 2D(g)

is plotted against absolute temperature T in figure as: ln K Vs (1/T)

(a) the forward reaction is exothermic

(b) the forward reaction is endothermic

(c) the slope of line is proportional to H

(d) adding ‘A’ favours forward reaction

14. For the reaction 2 2H g I g 2HI g , the equilibrium can be shifted in favour of product by

(a) Increasing the 2H (b) Increasing the catalyst

(c) Increasing the 2I (d) By using the pressure

15. In a reaction 2 2 4A g 4B g 2AB g , H 0 . The formation of 4AB is favoured by

(a) Low temperature and high pressure (b) High temperature and low pressure

(c) Low temperature and low pressure (d) High temperature and high pressure

16. For which of the following reactions at equilibrium at constant temperature, doubling the volume

will cause a shift to the right?

(a) 2 4 2N O g 2NO g (b) 3 2CaCO s CaO s CO g

(c) 2 22CO g O g 2CO g (d) 2 2N g O g 2NO g

17. Which of the following statements is/are wrong?

(a) At equilibrium, concentrations of reactants and products become constant because the reaction

stops.

(b) Addition of catalyst speeds up the forward reaction more than the backward reaction.

(c) Equilibrium constant of an exothermic reaction decreases with increase intemperature.

(d) pK is always greater than cK .

SECTION-III (Paragraph Type)

This section contains 2 groups of questions. Each question has 4 choices (A), (B), (C) and (D) for its answer, out of which ONLY ONE is correct. (+3, -1)

2 2 3N g 3H g 2NH g ; H 22.4kJ

The pressure inside the chamber is 100 atm and temperature at 300K.

18. If pK for the given reaction is 51.44 10 , then the value of cK will be:

(a)

51

2

1.44 10mol L

0.082 500

(b)

51

2

1.44 10mol L

8.314 200

(c)

51

2

1.44 10mol L

0.082 700 s

(d) none of these

19. The preparation of ammonia by Haber’s process is an exothermic reaction. If the preparation follows

the following temperature-pressure relationship for its % yield. Then for temperature 1 2T ,T , and 3T

the correct option is:

(a) 3 2 1T T T (b) 1 2 3T T T (c) 3 2 1T T T (d) 1 2 3T T T

SECTION-IV (Integer Answer Type)

This section contains 2 questions. The answer to each of the questions is a single digit integer, ranging from 0 to 9. The correct digit below the question number in the ORS is be bubbled. (+4, 0)

20. For the reaction A B C , the rate constants for the forward and the reverse reactions are 24 10

and 22 10 respectively. The value of equilibrium constant K for the reaction would be

21. One mole of ethanol is treated with one mole of ethanoic acid at o25 C . Half of the acid changes into ester at equilibrium. The equilibrium constant for the reaction will be.

1. a 2. c 3. d 4. b 5. b

6. c 7. c 8. c 9. c 10. a

11. a, b, c 12. b 13. a, c 14. a, c 15. a

16. a, b 17. a, b, d 18. d 19. c 20. 2.

21. 1