MCQs for Class 11 Chemistry with Answers Chapter 6 Thermodynamics

MCQs For Class 11 Chemistry With Answers

1. Which of the following are not state functions?
(I) q + w           (II) q                (III) w              (IV) H – TS
(a) (I), (II) and (III)        (b) (II) and (III)                         (c) (I) and (IV)              (d) (II), (III) and (IV)
Ans 1. (b)
State functions or state variables are those which depend only on the state of the system and not on how the state was reached.

q + w = ∆U (internal energy), H – TS = G (free energy), Both are State functions.
Path function depends on the path followed during a process. Work and heat are the path functions.

2. In a closed insulated container a liquid is stirred with a paddle to increase the temperature, which of the following is true?
(a) ΔE = W ≠ 0, q = 0    (b) ΔE = W = q ≠ 0        (c) ΔE = 0, W = q ≠ 0    (d) W = 0, ΔE = q ≠ 0
Ans 2. (a)
The mathematical form of the first law of thermodynamics: q = ΔE + W
Since the system is closed and insulated, q = 0
Paddle work is done on the system. ؞ W ≠ 0.
Temperature and hence internal energy of the system increases.  ΔE ≠ 0.

3. Which of the following is the correct equation?
(a) ΔU = ΔW + ΔQ       (b) ΔU = ΔQ – W          (c) ΔW = ΔU + ΔQ       (d) None of these
Ans 3. (b)
This is the mathematical relation of the first law of thermodynamics. Here ΔU = change in internal energy;
ΔQ = Heat absorbed by the system and W = work done by the system.

4. Which of the following does not come under the preview of thermodynamics?
(a) Predicting the feasibility of chemical change
(b) Predicting the extent of the chemical change
(c) Rate at which a chemical change occurs at a particular set of conditions
(d) Effect of temperature on the extent of reaction
Ans 4. (c) Rate at which a chemical change occurs at a particular set of conditions

5. Which among the following state functions is an extensive property of the system?
(a) Temperature            (b) Volume       (c) Refractive index       (d) Viscosity
Ans 5. (b) Volume

6. A chemical process is carried out in a thermostat maintained at 25°C. The process may be termed as
(a) Isobaric process       (b) Isoentropic process              (c) Adiabatic process     (d) Isothermal process
Ans 6. (d) Isothermal Process

7. Heat produced in calories by the combustion of one gram of carbon is called
(a) Heat of combustion of carbon
(b) Heat of formation of carbon
(c) Calorific value of carbon
(d) Heat of production of carbon
Ans 7. (c) It is the definition of calorific value.

8. Conditions of standard state used in thermochemistry is
(a) 0 ⁰C and 1 atm         (b) 20 ⁰C and 1 atm       (c) 25 ⁰C and 1 atm        (d) 0 K and 1 atm
Ans 8. (c) 25 ⁰C and 1 atm

9. The correct option for free expansion of an ideal gas under adiabatic condition is
(a) q = 0, ΔT = 0 and w = 0
(b) q = 0, ΔT < 0 and w > 0
(c) q < 0, ΔT = 0 and w = 0
(d) q > 0, ΔT > 0 and w > 0
Ans 9. (a)
For free expansion of an ideal gas, P_ex = 0, w = –P_exΔV = 0 For adiabatic process, q = 0 According to first law of thermodynamics,
ΔU = q + w = 0.
As internal energy of an ideal gas is a function of temperature, ΔU = 0, ؞ ΔT = 0

10. Under isothermal conditions, a gas at 300 K expands from 0.1 L to 0.25 L against Steroid Acne: Causes, Treatment and Prevention Tips – Health and Natural Healing Tips boldenone undecylenate for sale anabolic steroid use female, side effects of anabolic steroids in females include – inspire notion a constant external pressure of 2 bar. The work done by the gas is [Given that 1 L bar = 100 J]
(a) 30 J                         (b) –30 J                       (c) 5 kJ                         (d) 25 J
Ans 10. (b)
The expansion of a gas against a constant external pressure is an irreversible process. The work done in an irreversible process
= – P_ext ΔV = – P_ext (V₂ – V₁) = –2 (0.25 – 0.1) = – 2 × 0.15 L bar
= – 0.30 × 100 J = – 30 J

MCQs For Class 11 Chemistry With Answers

11. A gas expands isothermally and reversibly. The work done by the gas is
(a) Zero
(b) Maximum
(c) Minimum
(d) Cannot be predicted
Ans 11. (b) Maximum

12. Which is correct about isothermal expansion of an ideal gas?
(a) W_rev = W_irr
(b) W_rev + W_irr = 0
(c) W_rev > W_irr
(d) q_rev = q_irr
Ans 12. (c) W_rev > W_irr

13. A mixture of two moles of carbon monoxide and one mole of oxygen, in a closed vessel is ignited to convert the carbon monoxide to carbon dioxide. If ΔH is the enthalpy change and DE is the change in internal energy, then
(a) ΔH > ΔE
(b) ΔH < ΔE
(c) ΔH = ΔE
(d) The relationship depends on the capacity of the vessel
Ans 13. (b)
The formation of CO₂ from CO is an exothermic reaction; heat is evolved from the system, i.e., energy is lowered. Thus, exothermic reactions occur spontaneously on account of the decrease in enthalpy of the system. Thus, ΔE > ΔH.

14. Which of the following is always negative for an exothermic reaction?
(a) ΔH                          (b) ΔS                           (c) ΔG                          (d) None of these
Ans 14. (a) ΔH.

15. The work done during the expansion of a gas from a volume of 4 dm³ to 6 dm³ against a constant external pressure of 3 atm is (1 L atm = 101.32 J)
(a) – 6 J                        (b) – 608 J                    (c) + 304 J                    (d) – 304 J
Ans 15. (b)
Work = – P_ext × volume change = –3 × (6 – 4) × 101.32 = 6 × 101.32 = – 607.92 J ≈ – 608 J

16. For the reaction, C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l) which one is true?
(a) ΔH = ΔE – RT         (b) ΔH = ΔE + RT         (c) ΔH = ΔE + 2RT       (d) ΔH = ΔE – 2RT
Ans 16. (a)
ΔH = ΔE + PΔV also PV = nRT (ideal gas equation) or PΔV = Δ_ng RT
Δ_ng = Change in number of gaseous moles
ΔH = ΔE + Δ_ng RT ⇒ Δ_ng = 2 – 3 = –1 ⇒ ΔH = ΔE – RT

17. One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1 liter to 10 liters. The DE for this process is (R = 2 cal mol^–1 K^–1)
(a) 1381.1 cal                (b) zero                         (c) 163.7 cal                  (d) 9 L atm
Ans 17. (b)
Change in internal energy depends upon temperature. At constant temperature, the internal energy of the gas remains constant, so  ΔE = 0.

MCQs For Class 11 Chemistry With Answers

18. For the reaction, N₂ + 3H₂ → 2NH₃, ΔH =?

(a) ΔE + 2RT                (b) ΔE – 2RT                (c) ΔH = RT                  (d) ΔE – RT
Ans 18. (b)
_Δng = 2 – 4 = –2, ΔH = ΔE – 2RT

19. Standard enthalpy of vaporization D_vapH° for water at 100°C is 40.66 kJ mol^–1. The internal energy of vaporization of water at 100°C (in kJ mol^–1) is
(a) +37.56                     (b) – 43.76                    (c) + 43.76                    (d) + 40.66
(Assume water vapour to behave like an ideal gas)
Ans 19. (a)
_ΔvapH° = 40.66 kJ mol^–1
T = 100 + 273 = 373 K,
ΔE = ?
ΔH = ΔE + Δ_ng RT ⇒ ΔE = ΔH – Δ_ng RT
_Δng = Number of gaseous moles of products – Number of gaseous moles of reactants
H₂O (l) ↔ H₂O (g)
_Δng = 1 – 0 = 1
ΔE = ΔH – RT
ΔE = (40.66 × 10³) – (8.314 × 373) = 37559 J/mol = 37.56 kJ/mol

20. Which of the following statement is false?
(a) Internal energy of an ideal gas depends only on the temperature.
(b) The relation between ΔU and ∆H is ∆H = ΔU + PΔV.
(c) Heat of a reaction at constant pressure is equal to H_R – H_P.
(d) Heats of reaction at constant pressure (∆H) and at constant volume (ΔU) are related as ∆H – ΔU = Δ_ngRT.
Ans 20. (c) Heat of a reaction at constant pressure is equal to H_R – H_P.

MCQs For Class 11 Chemistry With Answers