Equilibrium · Question 16

Consider a weak base 'B' of pKb = 5.699. 'x' mL of 0.02 M HCl and 'y' mL of 0.02 M weak base 'B' are mixed to make 100 mL of a buffer of pH 9 at 25 . The values of 'x' and 'y' respectively are : [Given : 2 = 0.3010, 3 = 0.4771, 5 = 0.699]

1. arraycc x & y \ 42.7 & 57.3 array
2. arraycc x & y \ 14.3 & 85.7 array
3. arraycc x & y \ 85.7 & 14.3 array
4. arraycc x & y \ 11.1 & 88.9 array

Consider the dissociation equilibrium of the following weak acid HA H+(aq) + A-(aq) If the pKa of the acid is 4, then the pH of 10 mM HA solution is . (Nearest integer) [Given: The degree of dissociation can be neglected with respect to unity]

Observe the following equilibrium in a 1 L flask. A(g) B(g) At T(K), the equilibrium concentrations of A and B are 0.5 M and 0.375 M respectively. 0.1 moles of A is added into the flask and heated to T(K) to establish the equilibrium again. The new equilibrium concentrations (in M) of A and B are respectively

1. 0.742, 0.557
2. 0.367, 0.275
3. 0.53, 0.4
4. 0.557, 0.418

Consider two Group IV metal ions X2+ and Y2+. A solution containing 0.01 M X2+ and 0.01 M Y2+ is saturated with H2S. The pH at which the metal sulphide YS will form as a precipitate is . (Nearest integer) (Given: Ksp(XS) = 1 10-22 at 25 , Ksp(YS) = 4 10-16 at 25 , [H2S] = 0.1 M in solution, Ka1 Ka2(H2S) = 1.0 10-21, 2 = 0.30, 3 = 0.48, 5 = 0.70)

Consider the following gaseous equilibrium in a closed container of volume 'V' at T(K). P2(g) + Q2(g) 2PQ(g) 2 moles each of P2(g), Q2(g) and PQ(g) are present at equilibrium. Now one mole each of 'P2' and 'Q2' are added to the equilibrium keeping the temperature at T(K). The number of moles of P2, Q2 and PQ at the new equilibrium, respectively, are

1. 2.56, 1.62, 2.24
2. 2.67, 2.67, 2.67
3. 1.21, 2.24, 1.56
4. 1.66, 1.66, 1.66

Consider the general reaction given below at 400 K x A(g) y B(g). The values of Kp and Kc are studied under the same condition of temperature but variation in x and y. (i) Kp = 85.87 and Kc = 2.586 appropriate units (ii) Kp = 0.862 and Kc = 28.62 appropriate units The values of x and y in (i) and (ii) respectively are :

1. array|c|c| (i) & (ii) \ 1,2 & 2,1 \ array
2. array|c|c| (i) & (ii) \ 1,3 & 2,1 \ array
3. array|c|c| (i) & (ii) \ 3,1 & 3,1 \ array
4. array|c|c| (i) & (ii) \ 4,1 & 4,1 \ array

For the following gas phase equilibrium reaction at constant temperature, NH3(g) 1/2 N2(g) + 3/2 H2(g) if the total pressure is 3 atm and the pressure equilibrium constant (Kp) is 9 atm, then the degree of dissociation is given as (x 10-2 )-1/2. The value of x is . (nearest integer)

X2(g) + Y2(g) 2Z(g) X2(g) and Y2(g) are added to a 1 L flask and it is found that the system attains the above equilibrium at T(K) with the number of moles of X2(g), Y2(g) and Z(g) being 3, 3 and 9 mol respectively (equilibrium moles). Under this condition of equilibrium, 10 mol of Z(g) is added to the flask and the temperature is maintained at T(K). Then the number of moles of Z(g) in the flask when the new equilibrium is established is . (Nearest integer)

Dissociation of a gas A2 takes place according to the following chemical reaction. At equilibrium, the total pressure is 1 bar at 300 K. A2(g) 2A(g) The standard Gibbs energy of formation of the involved substances has been provided below: arraycc Substance & Gf /kJ mol-1 \ A2 & -100.00 \ A & -50.832 array The degree of dissociation of A2(g) is given by (x 10-2)1/2 where x = . (Nearest integer). [ Given : R = 8 J mol-1 K-1, 2 = 0.3010, 3 = 0.48 ] Assume degree of dissociation is not negligible.

Which of the following mixture gives a buffer solution with pH = 9.25 ? Given : pKb (NH4OH) = 4.75

1. 0.5 M NH4OH (0.2 L) + 0.2 M HCl (0.5 L)
2. 0.2 M NH4OH (0.5 L) + 0.1 M HCl (0.5 L)
3. 0.2 M NH4OH (0.4 L) + 0.1 M HCl (1 L)
4. 0.4 M NH4OH (1 L) + 0.1 M HCl (1 L)