11th Chemistry - Book Back Answers - Unit 8 - English Medium Guides

 

 

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Tamil Nadu Board 11th Standard Chemistry - Unit 8 : Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 8 – Chemistry from the Tamil Nadu State Board 11th Standard Chemistry textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Chemistry Unit 8 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 11 students! Prepare well and aim for top scores. Thank you!

Unit 8 :Physical and Chemical Equilibrium

I. Choose the best answer.

1. If K_b and K_r for a reversible reaction are 0.8x10^{- 5} and 1.6x10 ^-4 respectively, the value of the equilibrium constant is,

a) 20

b) 0.2 x10^-1

c) 0.05

d) none of these

Answer Key:

a) 20

 

2. At a given temperature and pressure, the equilibrium constant values for the equilibrium

$3{\mathrm{A}}_2+{\mathrm{B}}_2+2\mathrm{C} \stackrel{{\mathrm{K}}_1}{\leftrightharpoons } 2{\mathrm{A}}_3\mathrm{BC} \mathrm{and}$

The relation between K₁ and K₂ is

a) ${\mathrm{K}}_1 =\frac{1}{\sqrt{{\mathrm{K}}_2}}$

b)${\mathrm{ K}}_2={\mathrm{K}}_1^{\raisebox{1ex}{$-1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$

c) ${\mathrm{K}}_1^2=2{\mathrm{K}}_2$

d) $\frac{{\mathrm{K}}_1}{2}={\mathrm{K}}_2$

Answer Key:

b)${\mathrm{ K}}_2={\mathrm{K}}_1^{\raisebox{1ex}{$-1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$

 

3. The equilibrium constant for a reaction at room temperature is K₁ and that at 700 K is K_{2 .} If K₁> K₂then
a) The forward reaction is exothermic
b) The forward reaction is endothermic
c) The reaction does not attain equilibrium
d) The reverse reaction is exothermic

Answer Key:

a) The forward reaction is exothermic

 

4. The formation of ammonia from N₂ (g) and H₂g) is a reversible reaction
    N₂(g) + 3H₂(g) $\leftrightharpoons$ 2NH₃(g) + Heat
What is the effect of increase of temperature on this equilibrium reaction
a) equilibrium is unaltered
b) formation of ammonia is favoured
c) equilibrium is shifted to the left
d) reaction rate does not change 

Answer Key:

c) equilibrium is shifted to the left

 

5. Solubility of carbon dioxide gas in cold water can be increased by
a) increase in pressure
b) decrease in pressure
c) increase in volume
d) none of these

Answer Key:

a) increase in pressure

6 Which one of the following is incorrect statement?
a) for a system at equilibrium, Q is always less than the equilibrium constant
b) equilibrium can be attained from either side of the reaction
c) presence of catalyst affects both the forward reaction and reverse reaction to the same extent
d) Equilibrium constant varied with temperature

Answer Key:

a) for a system at equilibrium, Q is always less than the equilibrium constant

7. K₁ and K₂ are the equilibrium constants for the reactions respectively

N₂(g)+O₂(g)$\stackrel{{\mathrm{K}}_1}{\leftrightharpoons }$2NO(g)
2NO(g)+O₂(g)$\stackrel{{\mathrm{K}}_2}{\leftrightharpoons }$2NO₂(g)

What is the equilibrium constant for the reaction NO₂(g)$\leftrightharpoons$1/2N₂(g)+O₂(g)
a) $\frac{1}{\sqrt{{\mathrm{K}}_1{\mathrm{K}}_2}}$
b) $({\mathrm{K}}_1={\mathrm{K}}_2{)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$
c) $\frac{1}{2{\mathrm{K}}_1{\mathrm{K}}_2}$
d) 

Answer Key:

 a) $\frac{1}{\sqrt{{\mathrm{K}}_1{\mathrm{K}}_2}}$

8. In the equilibrium,
2A(g) ⇌ 2B(g) + C2(g)  2A(g)
the equilibrium concentrations of A, B and C₂ at 400 K are 1 × 10^-4 M, 2.0 ×10^-3 M, 1.5 × 10^-4 M respectively. The value of K_C for the equilibrium at 400 K is
a) 0.06
b) 0.09
c) 0.62
d) 3 x 10^-2

Answer Key:

a) 0.06 

 

9. An equilibrium constant of 3.2 x10^-6 for a reaction means, the equilibrium is
a) largely towards forward direction
b) largely towards reverse direction
c) never established
d) none of these

Answer Key:

b) largely towards reverse direction 

 
10. $\frac{{\mathrm{K}}_{\mathrm{C}}}{{\mathrm{K}}_{\mathrm{P}}}$ for the reaction

N₂(g) + 3H₂(g) ⇌2NH₃(g) is
a) $\frac{1}{\mathrm{RT}}$
b) $\sqrt{\mathrm{RT}}$
c) RT
d) (RT)²

Answer Key:

d) (RT)² 

11. For the reaction AB (g) ⇌ A(g) + B(g), at equilibrium, AB is 20% dissociated at a total pressure of P, The equilibrium constant KP is related to the total pressure by the expression
a) P = 24 K_P
b) P = 8 K_P
c) 24 P = K_P 
d) none of these

Answer Key:

a) P = 24 K_P 

 
12. In which of the following equilibrium, K_P and K_C are not equal?
a) 2 NO(g) ⇌ N₂(g) + O₂(g)
b) SO₂ (g) + NO₂ ⇌ SO₃(g) + NO(g)
c) H₂(g) + I₂(g) ⇌ 2HI(g)
d) PCl₅ (g) ⇌ PCl₃(g) + Cl₂(g) 

Answer Key:

d) PCl₅ (g) ⇌ PCl₃(g) + Cl₂(g)  

 
13. If x is the fraction of PCl₅ dissociated at equilibrium in the reaction
PCl₅ ⇌ PCl₃ + Cl₂
then starting with 0.5 mole of PCl₅, the total number of moles of reactants and      
products at equilibrium is
a) 0.5 – x 
b) x + 0.5
c) 2x + 0.5 
d) x + 1

Answer Key:

 b) x + 0.5

 

14. The values of K_p1 and K_p2 for the reactions
X ⇌ Y + Z
A ⇌ 2B are in the ratio 9 : 1 if degree of dissociation and initial concentration 
of X and A be equal then total pressure at equilibrium P₁, and P₂ are in the 
ratio
a) 36 : 1
b) 1 : 1
c) 3 : 1 
d) 1 : 9 

Answer Key:

a) 36 : 1 

 
15. In the reaction,
Fe (OH)₃ (s) ⇌ Fe³⁺(aq) + 3OH^–(aq),
if the concentration of OH^– ions is decreased by ¼ times, then the  equilibrium concentration of Fe⁺³ will
a) not changed
b) also decreased by ½ times
c) increase by 4 times
d) increase by 64 times

Answer Key:

d) increase by 64 times 

 
16. Consider the reaction where K_p = 0.5 at a particular temperature

PCl₅(g) ⇌ PCl₃ (g) + Cl₂ (g)

if the three gases are mixed in a container so that the partial pressure of each gas is initially 1 atm, then which one of the following is true
a) more PCl₃ will be produced
b) more Cl₂ will be produced
c) more PCl₅ will be produced
d) none of these

Answer Key:

c) more PCl₅ will be produced 

17. Equimolar concentrations of H₂ and I₂ are heated to equilibrium in a 1 litre flask. What percentage of initial concentration of H₂ has reacted at equilibrium if rate constant for both forward and reverse reactions are equal 
a) 33% 
b) 66%
c) (33)² % 
d) 16.5 % 

Answer Key:

a) 33%  

18. In a chemical equilibrium, the rate constant for the forward reaction is 2.5 x10² and the equilibrium constant is 50. The rate constant for the reverse reaction is, 
a) 11.5
b) 5
c) 2x 10 ²
d) 2x10^{- 3}

Answer Key:

b) 5 

 
19. Which of the following is not a general characteristic of equilibrium involving physical process
a) Equilibrium is possible only in a closed system at a given temperature
b) The opposing processes occur at the same rate and there is a dynamic but stable condition
c) All the physical processes stop at equilibrium
d) All measurable properties of the system remains constant

Answer Key:

c) All the physical processes stop at equilibrium 

20. For the formation of Two moles of SO₃(g) from SO₂ and O₂ the equilibrium constant is K₁. The equilibrium constant for the dissociation of one mole of SO₃ into SO₂and O₂ is
a) $\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{${\mathrm{K}}_1$}\right.$
b) ${\mathrm{K}}_1^2$
c)
d)$\frac{{\mathrm{K}}_1}{2}$

Answer Key:

c) 

 
21. Match the equilibria with the corresponding conditions,
i) Liquid ⇌ Vapour
ii) Solid ⇌ Liquid
iii) Solid ⇌ Vapour
iv) Solute (s) ⇌ Solute (Solution)
1) melting point
2) Saturated solution
3) Boiling point
4) Sublimation point
5) Unsaturated solution

Answer Key:

(b) 3    1    4    2

22. Consider the following reversible reaction at equilibrium, A+ B ⇌ C, If the concentration of the reactants A and B are doubled, then the equilibrium constant will

a) be doubled
b) become one fourth
c) be halved
d) remain the same

Answer Key:

d) remain the same 

 
23. [Co(H₂O)₆]₂+ (aq) (pink) + 4Cl^– (aq) ⇌ [CoCl₄]₂^– (aq) (blue)+ 6 H₂O (l) In the above reaction at equilibrium, the reaction mixture is blue in colour at room temperature. On cooling this mixture, it becomes pink in colour. On the basis of this information, which one of the following is true?
a) ΔH > 0 for the forward reaction
b) ΔH = 0 for the reverse reaction
c) ΔH < 0 for the forward reaction
d) Sign of the ΔH cannot be predicted based on this information. 

Answer Key:

a) ΔH > 0 for the forward reaction 

24. The equilibrium constants of the following reactions are :
N₂ + 3H₂ ⇌ 2NH₃      ; K₁
N₂ + O₂ ⇌ 2NO         ; K₂
H₂ + ½O₂ ⇌ H₂O       ; K₃
The equilibrium constant (K) for the reaction ;
2NH₃+5/2O₂$\stackrel{{\mathrm{K}}_{}}{\leftrightharpoons }$2NO+3H₂O

a) ${\mathrm{K}}_2^3\raisebox{1ex}{${\mathrm{K}}_3$}\!\left/ \!\raisebox{-1ex}{${\mathrm{K}}_2$}\right.$

b)${\mathrm{ K}}_1\raisebox{1ex}{${\mathrm{K}}_3^3$}\!\left/ \!\raisebox{-1ex}{${\mathrm{K}}_2$}\right.$

c) ${\mathrm{K}}_2\raisebox{1ex}{${\mathrm{K}}_3^3$}\!\left/ \!\raisebox{-1ex}{${\mathrm{K}}_1$}\right.$

d) $\raisebox{1ex}{${\mathrm{K}}_2{\mathrm{K}}_3$}\!\left/ \!\raisebox{-1ex}{${\mathrm{K}}_1$}\right.$

Answer Key:

c) ${\mathrm{K}}_2\raisebox{1ex}{${\mathrm{K}}_3^3$}\!\left/ \!\raisebox{-1ex}{${\mathrm{K}}_1$}\right.$

 

25. A 20 litre container at 400 K contains CO₂ (g) at pressure 0.4 atm and an excess of SrO (neglect the volume of solid SrO). The volume of the container is now decreased by moving the movable piston fitted in the container. The maximum volume of the container, when pressure of CO₂ attains its maximum value will be:
Given that : SrCO₃ (S) ⇌ SrO (S) + CO₂(g)
K_P = 1.6 atm (NEET 2017)
a) 2 litre 
b) 5 litre
c) 10 litre 
d) 4 litre

Answer Key:

b) 5 litre 

II. Short Answer Questions

11th Chemistry

III. Long Answer Questions

11th Chemistry

IV. Exercise

11th Chemistry