Chemical Equilibrium Important Questions And Answers

  Chemical Equilibrium Important Questions And Answers:

Chemical Equilibrium is the most important and interesting chapter of Chemistry. So the practice set of Chemical Equilibrium with Important Questions And Answers helps students of class 11 and also for students studying for various competitive exams. Students are advised to practice and understand all the questions accordingly.

1. A reversible reaction is one which:

a) Proceeds in one direction

b) Proceeds in both directions

c) Proceeds spontaneously

d) All the statements are wrong

ANS:

The reversible reaction always attains equilibrium which proceeds both sides and never goes for completion.

2. The reaction CaCO₃ ⇌  CaO +CO₂(g) goes to completion in lime because:

a) Of the high temperature

b) CaO is more stable than CaCO₃

c)  CaO is not dissociated

d) CO₂ escapes continuously

ANS:

In lime CO₂ escaping regularly so reaction proceeds in a forward direction.

3. In the given reaction  N₂ + O₂ ⇌ 2NO, equilibrium means:

a) The concentration of reactants is changing whereas a concentration of products is constant

b) The concentration of all substances is constant

c) The concentration of reactants is constant whereas a concentration of products is changing

d) The concentration of all substances is changing

4. All reactions which have chemical disintegration:

a) Is reversible

b) Is reversible and endothermic

c) Is exothermic

d) Is reversible or irreversible and endothermic or exothermic

5. Amongst the following chemical reactions, the irreversible reaction is:

a) AgNaO₃ + NaCl ⇌ AGCl + NaNO₃

b) H₂ + I₂  ⇌ HI

c) CaCO₃ ⇌ CaO + CO₂

d) O₂ + 2SO₂  ⇌2SO₃

ANS:

The reaction is not reversible.

6. When the rate of forward reaction becomes equal to backward reaction, this state is termed as:

a) Chemical equilibrium

b) Reversible state

c) Equilibrium

d) All of these

7.In chemical reaction A⇌B, the system will be known in equilibrium when

a) Completely changes to B

b) 50% of A changes to B

c) The rate of change of A to B and B to A on both the sides are the same

d) Only 10% of A changes to B

ANS:

When the rate of the forward reaction is equal to rate of backward reaction the reaction is said to be in equilibrium.

8.Which of the following conditions represents an equilibrium:

a) freezing of ice in an open vessel, the temperature of ice is constant

b) Few drops of water are present along with the air in a balloon, the temperature of a balloon is constant

c) Water is boiling in an open vessel over a stove, the temperature of the water is constant

d) All the statements A, B and C are correct for the equilibrium

ANS:

Equilibrium can be achieved only in closed vessel.

9.Under a given set of experimental conditions, with an increase in the concentration of the reactants, the rate of a chemical reaction.

a) Decreases

b) Increases

c) Remains unaltered

d) First decreases and then increases

10. The active mass of 64 gm of HI in a two-liter flask would be:

a) 2

b) 1

c) 5

d) 0.25

ANS:

\(\frac{64}{{128}\times{2}}\) = 0.25

Active mass is the concentration in  \(\frac{ moles}{litre}\).

11.In the th In the thermal decomposition of potassium chlorate given as  2KClO₃ → 2KCl + 3O₂, law of mass action KCl+3O₂, the law of mass action.

a) Cannot be applied

b) Can be applied

c) Can be applied at low-temperature

d) Can be applied at a high temp. and pressure

12.Theory of active mass indicates that the rate of a chemical reaction is directly proportional to the.

a) Equilibrium constant

b) Properties of reactants

c) Volume of apparatus

d) Concentration of reactants

13. For the system 3A+2B ⇌ C, the expression for the equilibrium constant is:

a) \(\frac{[3A]\times[2B]}{C}\)

b) \(\frac{C}{{3A}\times{2B}}\)

c) \(\frac{[A^3]\times[B^2]}{C}\)

d) \(\frac{C}{{A^3}\times{B^2}}\)

ANS:

Equilibrium constant for the reaction ,  3A + 2B  ⇌ C is

K =  \(\frac{C}{{A^3}\times{B^2}}\)

14.4 moles of A are mixed with 4 moles of B.At equilibrium for the reaction  A+B ⇌C+ D, 2 moles of C and D are formed.The equilibrium constant for the reaction will be:

a) \(\frac{1}{4}\)

b) \(\frac{1}{2}\)

c) 1

d) 4

ANS:

Conce	A+B	⇌	C+D
Initial conc.	4,   4		0    0
After T time conc.	(4-2) (4-2)		2,   2

\(\frac{[C]\times[D]}{[A\times[B]}\)

15.In which of the following, the reaction proceeds towards completion:

16.The equilibrium constant for the given reaction H₂ +I₂ ⇌ 2HI is correctly given by the expression:\(\\\)

17. The unit of equilibrium constant K for the reaction A+B⇌C would be: \(\\\)

18.The decomposition of  N₂O₄ to NO₂ is carried out at 280K in Chloroform. When equilibrium has been  established, 0.2 mol of N₂O₄ and 2×10⁻³ mol of NO₂ are present in 2-liter solution. The equilibrium constant for reaction  N₂O₄ ⇌  2NO₂ is:\(\\\)

19. Equilibrium constants K₁and K₂ for the following equilibria NO(g) + \(\frac{1}{2}\) O₂ \(\overset{k_1}{\rightarrow}\) NO₂(g) and 2NO2(g) \(\overset{k_2}{\rightarrow}\) 2NO(g)+O₂(g) are related as: \(\\\)

20.The relation between equilibrium constant K_p and K_c is:

21.K for the synthesis of HI is 50.K for dissociation of HI is:

22. The le-chatelier principle is applicable:

23.On the velocity in a reversible reaction, the correct explanation of the effect of catalyst is:

a) It provides a new reaction path of low activation energy.

b) It increases the kinetic energy of reacting molecules.

c) It displaces the equilibrium state on the right side.

d) It decreases the velocity of the backward reaction.

ANS:

Effect of catalyst is that it attains equilibrium quickly by providing a new reaction path of low activation energy. It does not alter the state of equilibrium.

24. Which of the following conditions is favourable for the production of ammonia by Haber’s process:

a) A high concentration of reactants.

b) Low temperature and high-pressure.

c) Continuous removal of ammonia.

d) All of these.

25. In N₂  + 3H₂ ⇌ 2NH₃ reversible reaction, an increase in pressure will favour:

a) A reaction in a forward direction.

b) A reaction in reverse direction.

c) Will not exert any effect.

d) In backward and forward direction equally.

26.In which of the following system, doubling the volume of the container causes a shift to the right.

a) H₂ (g)  + Cl₂ (g) =2HCl(g)

b) 2CO(g) + O₂(g) =2CO₂(g)

c) N₂(g) +3H₂(g)=2NH₃(g)

d) PCl₅ (g) ⇌ PCl₃(g) + Cl₂(g)

ANS:

Increase in volume, i.e., decrease in pressure shifts the equilibrium in the direction in which the number of moles increases ( positive)

27.Partial pressures of A, B, C and D on the basis of gaseous system A+2B ⇌ C+3D are A = 0.20; B = 0.10;  C = 0.30 and D = 0.50 atm. The numerical value of equilibrium constant is:

28. For which of the following reactions does the equilibrium constant depend on the units of concentration:

29.In a chemical equilibrium A + B ⇌ C + D, when one mole each of the two reactants are mixed, 0.6 moles each of the products are formed. The equilibrium constant calculated is:

31.If dissociation for reaction, PCl₅ ⇌ PCl₃ +Cl₂ is 20% at 1 atm. pressure.Calculate K_c.

a) 0.04

b) 0.05

c) 0.07

d) 0.06

ANS:

Kc =  \(\frac{[PCl_{3}][Cl_2]}{[PCl_5]}\\\)

\(\frac{[0.2]\times[0.2]}{[0.8]}\\\) = 0.05

32.At 700 K, the equilibrium constant Kp for the reaction  2SO_3(g) ⇌ 2SO_2(g)+O_2(g) is 1.80×10⁻³ and kPa is 14, (R = 8.314 Jk^-1 mol^-1). The numerical value in moles per litre of Kc for this reaction at the same temperature will be:

a) 3.09 × 10⁻⁷ \(\frac{mol}{litre}\\\)

b) 5.07 × 10⁻⁸ \(\frac{mol}{litre}\\\)

c) 8.18 × 10⁻⁹ \(\frac{mol}{litre}\\\)

d) 9.24 × 10⁻¹⁰ \(\frac{mol}{litre}\\\)

ANS:

2SO_3(g) ⇌ 2SO_2(g)+O_2(g)

Δn =3−2 =+1;  K_p  = 1.80×10⁻³

\((RT) ^{Δn}\) = (\(8.314\times700)^1\)

Kc = \(\frac{(K_p}{RT)}^{Δn}\\\)  = \(\frac{1.8\times 10^{-3}}{(8.314\times 700)^1}\)

(\(3.09\times10)^-7\\\) mole-litre.

33. At constant temperature, the equilibrium constant (Kp) for the decomposition reaction N₂O₄ ⇌2NO₂ is expressed byKP = \(\frac{4x^{2}P}{1-x^{2}}\\\) {where P = pressure, x= extent of decomposition. Which one of the following statements is true:

a) Kp increases with increase of P

b) Kp increases with increase of x

c) Kp increases with decrease of x

d) Kp remains constant with change in P and x                          

ANS:

K_p(equilibrium constant) is independent of pressure and concentration.

34 .One mole of a compound AB reacts with one mole of a compound CD according to the equation AB + CD ⇌ AD + CB.  When equilibrium had been established it was found that 34 mole each of reactant AB and CD had been converted to AD and CB. There is no change in volume. The equilibrium constant for the reaction.

a) \(\frac{9}{16}\\\)

b) \(\frac{1}{9}\\\)

c) \(\frac{16}{9}\\\)

d) 9

ANS: 

mole	AB + CD	⇌	AD + Cb
at t=0	1, 1		0, 0
at equilibrium	1- \(\frac{3}{4}\\\)  1- \(\frac{3}{4}\\\)		\(\frac{3}{4}\\\)

35. Chemical equations convey quantitative information on the:

38. Diffrence between Combination Reactions and Decomposition reaction