Equilibrium
Practice Question Answer Set 2
Q.1. Ka1, Ka2 and Ka3 are the respective ionisation constants for the following reactions.
H2S ⇌ H+ + HS–
HS– ⇌ H+ + S2–
H2S ⇌ 2H+ + S2–
Find the relationship among Ka1, Ka2 and Ka3.
Answer
The correct relationship between Ka1, Ka2 and Ka3 is
Ka3 = Ka1 × Ka2
Q.2. Write expressions for Kp and Kc for the decomposition reaction of calcium carbonate.
Answer
Taking active masses of solids to be unity,
Q.3. The ionization constant of HF, HCOOH and HCN at 298 K are 6.8 × 10–4, 1.8 × 10–4 and 4.8 × 10–9 respectively. Calculate the ionization constants of the corresponding conjugate base.
Answer
Q.4. Write the relation between Qc and Kc for reverse reaction.
Answer
Qc > Kc , for reverse reaction.
Q.5. We know that the relationship between Kc and Kp is
Kp = Kc(RT)∆ng
What would be the value of ∆ng for the reaction
NH4Cl(s) ⇌ NH3(g) + HCl(g)
Answer
∆ng = np – nr = 2 – 0 = 2
Q.6. Equilibrium constant for a reaction is 10. What will be the equilibrium constant for the reverse reaction?
Answer
Q.7. Write the expression for the equilibrium constant Kc for the following equilibrium :
3Fe(s) + 4H2O(g) ⇌ Fe3O4(s) + 4H2(g)
Answer
(concentration of solids is taken as unity)
Q.8. For the system 3A + 2B ⇌ C, what is the expression for equilibrium constant K?
Answer
Q.9. Differentiate between homogeneous and heterogeneous equilibrium giving examples.
Answer
Equilibrium is said to be homogeneous if reactants and products are in same phase, e.g.,
Equilibrium is said to be heterogeneous if reactants and products are in different phases, e.g.,
Q.10. Calculate (a) ∆G° and (b) the equilibrium constant for the formation of NO2 from NO and O2 at 298 K.
where ∆fG° (NO2) = 52.0 kJ mol–1,
