Q.1. Does the number of moles of reaction products increase, decrease or remain same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume?
(a) PCl5(g) ⇌ PCl3(g) + Cl2(g)
(b) CaO(s) + CO2(g) ⇌ CaCO3(s)
(c) 3Fe(s) + 4H2O(g) ⇌ Fe3O4(s) + 4H2(g)
Q.2. Which of the following reactions will get affected by increasing the pressure? Also, mention whether change will cause the reaction to go into forward or backward direction.
(i) COCl2(g) ⇌ CO(g) + Cl2(g)
(ii) CH4(g) + 2S2(g) ⇌ CS2(g) + 2H2S(g)
(iii) CO2(g) + C(s) ⇌ 2CO(g)
(iv) 2H2(g) + CO(g) ⇌ CH3OH(g)
(v) CaCO3(s) ⇌ CaO(s) + CO2(g)
(vi) 4 NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g)
Q.3. The equilibrium constant for the following reaction is 1.6 ×105 at 1024K
H2(g) + Br2(g) ⇌ 2HBr(g)
Find the equilibrium pressure of all gases if 10.0 bar of HBr is introduced into a sealed container at 1024K.
Q.4. Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:
CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g)
(a) Write as expression for Kp for the above reaction.
(b) How will the values of Kp and composition of equilibrium mixture be affected by
(i) increasing the pressure
(ii) increasing the temperature
(iii) using a catalyst ?
Q.5. Describe the effect of :
a) addition of H2
b) addition of CH3OH
c) removal of CO
d) removal of CH3OH
on the equilibrium of the reaction:
2H2(g) + CO(g) ⇌ CH3OH (g)
Q.6. At 473 K, equilibrium constant Kc for decomposition of phosphorus pentachloride, PCl5 is 8.3 ×10−3. If decomposition is depicted as,
PCl5(g) ⇌ PCl3(g) + Cl2(g)
∆rHo = 124.0 kJ mol–1
a) write an expression for Kc for the reaction.
b) what is the value of Kc for the reverse reaction at the same temperature ?
c) what would be the effect on Kc if
(i) more PCl5 is added
(ii) pressure is increased
(iii) the temperature is increased ?
Q.7. Dihydrogen gas used in Haber’s process is produced by reacting methane from natural gas with high temperature steam. The first stage of two stage reaction involves the formation of CO and H2. In second stage, CO formed in first stage is reacted with more steam in water gas shift reaction,
CO(g) + H2O(g) ⇌ CO2(g) + H2(g)
If a reaction vessel at 400 °C is charged with an equimolar mixture of CO and steam such that pCO = pH2O = 4.0 bar, what will be the partial pressure of H2 at equilibrium? Kp = 10.1 at 400°C.
Q.8. Predict which of the following reaction will have appreciable concentration of reactants and products:
a) Cl2(g) ⇌ 2Cl(g) K c = 5 ×10–39
b) Cl2(g) + 2NO(g) ⇌ 2NOCl(g) K c = 3.7 × 108
c) Cl2(g) + 2NO2(g) ⇌ 2NO2Cl(g) Kc = 1.8
Q.9. The value of Kc for the reaction 3O2(g) ⇌ 2O3(g) is 2.0 ×10–50 at 25°C. If the equilibrium concentration of O2 in air at 25°C is 1.6 ×10–2, what is the concentration of O3?
Q.10. The reaction, CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g) is at equilibrium at 1300 K in a 1L flask. It also contains 0.30 mol of CO, 0.10 mol of H2 and 0.02 mol of H2O and an unknown amount of CH4 in the flask. Determine the concentration of CH 4 in the mixture. The equilibrium constant, Kc for the reaction at the given temperature is 3.90.
Q.11. What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species:
HNO2, CN–, HClO4, F–, OH –, CO32–, and S2–
Q.12. Which of the followings are Lewis acids?
H2O, BF3, H+, and NH4+
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