Question 1
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure?

Question 2
What is K_c for the following equilibrium when the equilibrium concentration of each substance is: [SO₂]= 0.60 M,  [O₂] = 0.82 M  and  [SO₃] = 1.90 M ?
2SO_2(g) + O_2(g)   ↔   2SO_3(g)

Question 4
Write the expression for the equilibrium constant, K_c for each of the following reactions:
(i)   2NOCl (g)   ↔   2NO (g) + Cl₂ (g)
(ii)  2Cu(NO₃)₂ (s) ↔  2CuO (s) + 4NO₂ (g) + O₂ (g)
(iii) CH₃COOC₂H₅(aq) + H₂O(l) ↔  CH₃COOH (aq) + C₂H₅OH (aq)
(iv) Fe³⁺ (aq) + 3OH^– (aq) ↔  Fe(OH)₃ (s)
(v) I₂ (s) + 5F₂ ↔  2IF₅ 

Question 5
Find out the value of K_c for each of the following equilibria from the value of K_p:
(i) 2NOCl (g)  ↔  2NO (g) + Cl₂ (g);                   Kp  =  1.8 × 10^–2 at 500 K
(ii) CaCO₃ (s)  ↔  CaO(s) + CO₂(g);                  Kp  = 167 at 1073 K

Question 6
For the following equilibrium, K_c = 6.3 × 10¹⁴  at 1000 K
NO (g) + O₃ (g) ↔ NO₂ (g) + O₂ (g)
Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is K_c, for the reverse reaction?

Question 7
Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?

Question 8
Reaction between N₂ and O_2– takes place as follows:
2N₂ (g)  +  O₂ (g) ↔  2N₂O (g)
If a mixture of 0.482 mol N₂ and 0.933 mol of O₂ is placed in a 10 L reaction vessel and allowed to form N₂O at a temperature for which K_c = 2.0 × 10^–37, determine the composition of equilibrium mixture.

Question 9
Nitric oxide reacts with Br₂ and gives nitrosyl bromide as per reaction given below:
2NO (g) + Br₂ (g) ↔ 2NOBr (g)
When 0.087 mol of NO and 0.0437 mol of Br₂ are mixed in a closed container at constant temperature, 0.0518 mol of NOBr is obtained at equilibrium. Calculate equilibrium amount of NO and Br₂ .

Question 10
At 450K, K_p= 2.0 × 10¹⁰/bar for the given reaction at equilibrium.
2SO₂(g) + O₂(g) ↔ 2SO₃ (g)
What is K_c at this temperature ?

Question 11
A sample of HI_(g) is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of HI_(g) is 0.04 atm. What is K_p for the given equilibrium ?
2HI (g) ↔ H₂ (g) + I₂ (g)

Question 12
A mixture of 1.57 mol of N₂, 1.92 mol of H₂ and 8.13 mol of NH₃ is introduced into a 20 L reaction vessel at 500 K. At this temperature, the equilibrium constant, K_c for the reaction N₂ (g) + 3H₂ (g) ↔ 2NH₃ (g) is 1.7 × 10².
Is the reaction mixture at equilibrium? If not, what is the direction of the net reaction?

Question 15
At 700 K, equilibrium constant for the reaction:
H2 (g) + I2 (g) ↔ 2HI (g)
is 54.8. If 0.5 mol L^–1 of HI(g) is present at equilibrium at 700 K, what are the concentration of H₂(g) and I₂(g) assuming that we initially started with HI(g) and allowed it to reach equilibrium at 700K?

Question 16
What is the equilibrium concentration of each of the substances in the equilibrium when the initial concentration of ICl was 0.78 M ?
2ICl (g)  ↔  I₂ (g) + Cl₂ (g);     Kc = 0.14

Question 17
Kp = 0.04 atm at 899 K for the equilibrium shown below. What is the equilibrium concentration of C₂H₆ when it is placed in a flask at 4.0 atm pressure and allowed to come to equilibrium?
C₂H₆ (g) ↔ C₂H₄ (g) + H₂ (g)

Question 18
Ethyl acetate is formed by the reaction between ethanol and acetic acid and the equilibrium is represented as:
CH₃COOH (l) + C₂H₅OH (l) ↔ CH₃COOC₂H₅ (l) + H₂O (l)
(i) Write the concentration ratio (reaction quotient), Q_c, for this reaction (note: water is not in excess and is not a solvent in this reaction)
(ii) At 293 K, if one starts with 1.00 mol of acetic acid and 0.18 mol of ethanol, there is 0.171 mol of ethyl acetate in the final equilibrium mixture. Calculate the equilibrium constant.
(iii) Starting with 0.5 mol of ethanol and 1.0 mol of acetic acid and maintaining it at 293 K, 0.214 mol of ethyl acetate is found after sometime. Has equilibrium been reached?

Question 19
A sample of pure PCl5 was introduced into an evacuated vessel at 473 K. After equilibrium was attained, concentration of PCl5 was found to be 0.5 × 10^–1 mol L^–1. If value of Kc is 8.3 × 10^–3, what are the concentrations of PCl₃ and Cl₂ at equilibrium?
PCl₅ (g) ↔ PCl₃ (g) + Cl₂(g)

Question 20
One of the reaction that takes place in producing steel from iron ore is the reduction of iron(II) oxide by carbon monoxide to give iron metal and CO₂.
FeO (s) + CO (g) ↔ Fe (s) + CO₂ (g);   Kp = 0.265 atm at 1050K
What are the equilibrium partial pressures of CO and CO₂ at 1050 K if the initial partial pressures are: p_CO= 1.4 atm and P_co2 = 0.80 atm

Question 21
Equilibrium constant, Kc for the reaction
N2 (g) + 3H2 (g) ↔ 2NH₃ (g) at 500 K is 0.061
At a particular time, the analysis shows that composition of the reaction mixture is 3.0 mol L^–1 N₂, 2.0 mol L^–1 H₂ and 0.5 mol L^–1 NH₃.
Is the reaction at equilibrium?
If not in which direction does the reaction tend to proceed to reach equilibrium?

Question 22
Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:
2BrCl (g) ↔ Br₂ (g) + Cl₂ (g) for which K_c= 32 at 500 K.
If initially pure BrCl is present at a concentration of 3.3 × 10^–3 mol L^–1, what is its molar concentration in the mixture at equilibrium?

Question 25
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)

Question 26
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)

Question 28
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 ?

Question 29
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)

Question 30
At 473 K, equilibrium constant K_c for decomposition of phosphorus pentachloride, PCl₅ is 8.3 ×10^-3. If decomposition is depicted as,
PCl₅ (g) ↔  PCl₃ (g) + Cl₂ (g)          Δ_rH⁰ = 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 K_c if (i) more PCl5 is added (ii) pressure is increased (iii) the temperature is increased ?

Question 31
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 P_CO  = P_H2O = 4.0  bar, what will be the partial pressure of H₂ at equilibrium? K_p= 10.1 at 400°C.

Question 32
Predict which of the following reaction will have appreciable concentration of reactants and products:
a) Cl₂ (g)  ↔  2Cl (g)                             Kc = 5 ×10^–39
b) Cl₂ (g) + 2NO (g)  ↔  2NOCl (g)         Kc = 3.7 × 10⁸
c) Cl₂ (g) + 2NO₂ (g)  ↔  2NO₂Cl (g)      Kc = 1.8

Question 33
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?

Question 35
What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species:
HNO₂,  CN^– ,  HClO₄,  F ^–,  OH^–,  CO^2–₃  and  S^-

Question 36
Which of the followings are Lewis acids?  H₂O,  BF₃,  H⁺  and NH⁺₄

Question 37
What will be the conjugate bases for the Brönsted acids: HF, H₂SO₄ and HCO₃?

Question 38
Write the conjugate acids for the following Brönsted bases:  NH^–₂ , NH₃  and  HCOO^–.

Question 39
The species: H₂O, HCO^–₃, HSO^-₄  and NH₃ can act both as Brönsted acids and bases. For each case give the corresponding conjugate acid and base.

Question 40
Classify the following species into Lewis acids and Lewis bases and show how these act as Lewis acid/base:
(a) OH^–
(b) F^–
(c) H⁺
(d) BCl₃

Question 41
The concentration of hydrogen ion in a sample of soft drink is 3.8 × 10^–3 M. what is its pH?

Question 44
The ionization constant of phenol is 1.0 × 10^–10. What is the concentration of phenolate ion in 0.05 M solution of phenol? What will be its degree of ionization if the solution is also 0.01M in sodium phenolate?

Question 45
The first ionization constant of H₂S is 9.1 × 10^–8. Calculate the concentration of HS^– ion in its 0.1M solution. How will this concentration be affected if the solution is 0.1M in HCl also ? If the second dissociation constant of H₂S is 1.2 × 10^–13, calculate the concentration of S^2– under both conditions.

Question 48
Assuming complete dissociation, calculate the pH of the following solutions:
(a) 0.003 M HCl
(b) 0.005 M NaOH
(c) 0.002 M HBr
(d) 0.002 M KOH

Question 49
Calculate the pH of the following solutions:
(a) 2 g of TlOH dissolved in water to give 2 litre of solution.
(b) 0.3 g of Ca(OH)₂ dissolved in water to give 500 mL of solution.
(c) 0.3 g of NaOH dissolved in water to give 200 mL of solution.
(d) 1mL of 13.6 M HCl is diluted with water to give 1 litre of solution.