CBSE Class 11 Chemistry Thermodynamics MCQs Set D

Question. The succeeding operations that enable this transformation of states are 
(a) heating, cooling, heating, cooling
(b) cooling, heating, cooling, heating
(c) heating, cooling, cooling, heating
(d) cooling, heating, heating, cooling
Answer: c

Question. A gas expands from a volume of 1m³ to a volume of 2m³ against an external pressure of 10⁵ Nm^-2 . The work done by the gas will be 
(a) 10² kJ
(b) 10² J
(c) 10³ J
(d) 10⁵ kJ
Answer: a

Question. A gas undergoes a thermodynamical process but the volume of the gas does not change. What is the nature of this process ? 
(a) Isothermal
(b) Adiabatic
(c) Isobaric
(d) Isochoric
Answer: d

Question. An ideal gas expands in volume from 1 x 10^-3 m³ to 1 x 10^-2 m³ at 300 K against a constant pressure of 1 x 10⁵ Nm^-2 . The work done is
(a) – 9001
(b) – 900kJ
(c) 270kJ
(d) 900kJ
Answer: a

Question. An adiabatic process occurs in 
(a) open system
(b) closed system
(c) isolated system
(d) in all the given system
Answer: c

Question. Which one of the following is an exothermic reaction?
(a) N₂ (g) + O₂ (g )+ 180. 8kJ → 2NO(g) 
(b) N₂ (g)+ 3H₂ (g) – 92kJ → 2NH₃ (g)
(c) C(g) + H₂O(g) → CO(g) + H₂ (g) – 131.1 kJ
(d) C(graphite)+2S(s) → CS₂(l) – 91.9 kJ
Answer: b

Question. At 25°C, for the combustion of 1 mole of liquid benzene, the heat ofreaction at constant pressure is given by C₆H₆ (/) +15/2 O₂ (g) → 6CO₂ (g)+ 3H₂O (/),
(ΔH = 780980cal)
Calculate the heat of reaction at constant volume 
(a) 780.086 kcal
(b) – 780.086 kcal
(c) – 390.043 kcal
(d) 390.043 kcal
Answer: a

Question. A piston filled with 0.04 mole of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 37.0°C. As it does so, it absorbs 208 J of heat. The values of q and W for the process will be (R = 8.314 J/mol K, In 7.5 = 2.01) 
(a) q = + 208 J, W = – 208 J
(b) q = – 208 J, W = – 208 J
(c) q = – 208 J, W = + 208 J
(d) q = + 208 J, W = + 208 J
Answer: a

Question. IfC (s)+ O₂(g) → CO₂ (g);ΔH = r and l CO (g)+ 1/2 O₂ → CO₂ (g); ΔH =s, then the heat of 2 formation of CO is
(a) r+s
(b) r – s
(c) s – r
(d) rs
Answer: b

Question. C(s) + O₂ (g) → CO₂(g); ΔH = –94kcal
2CO(g) + O₂ → 2CO₂ (g); ΔH = –135.2 kcal
The heat of formation of CO (g) is 
(a) – 26.4 kcal
(b) 41.2 kcal
(c) 26.4 kcal
(d) 229.2 kcal
Answer: a

Question. Internal energy is sum of 
(a) kinetic energy and potential energy
(b) all types of energy of the system
(c) energy of internal system
(d) None of the above
Answer: b

Question. At 27° C one mole of an ideal gas is compressed isothermally and reversible from a pressure of 2 attn to 10 attn. The value of ΔE and q are ( R = 2 cal)
(a) 0, –965.84cal
(b) –965.84cal, –865.58cal
(c) + 865.58cal, –865.58cal
(d) +965.84cal, + 865.58cal
Answer: a

Question. Hess’s law is based on
(a) law of conservation of mass
(b) law of conservation of energy
(c) first law ofthem1odynamics
(d) None of the above
Answer: b

Question. The internal energy changes when a system goes from state A to B is 40 kJ/mol. If the system goes from A to B by a reversible path and returns to state A by an i.tTeversible path, what would be the net change in internal energy ?
(a) 40 kJ
(b) > 40 kJ 
(c) < 40 kJ
(d) Zero
Answer: d

Question. Mark out the enthalpy of formation of carbon monoxide (CO)
Given, C(s) + 1/2 O₂ (g) → CO(g),
ΔH = – 39.3 kJ/rnol
CO(g) + 1/2 O₂ (g) → CO₂ (g), ΔH = –282.8 kJ/ mol
(a) 110.5 kJ/mol
(b) 676.1 kJ/mol
(c) 282.8 kJ/mol
(d) 300.0 kJ/mol
Answer: a

Question. In an adiabatic process
(a) p.ΔV = 0
(b) q =+W
(c) ΔE = q
(d) q = 0
Answer: d

Question. A plot of In k against 1/T (abscissa) is expected to be a straight line with intercept on coordinate axis equal to 
(a) ΔS°/2.303R
(b) ΔS°/RE
(c) -ΔS°/R
(d) R x ΔS°
Answer: b

Question. A container of 1.0 L capacity filled with 1.0 mole of ideal gas is connected to an evacuated vessel of 9.0 L. Calculate change in entropy. (R = l.987 cal) 
(a) 0.188cal. K^-1 mol^-1
(b) 0.4576cal.K^-1 mol^-1
(c) 4.576cal. K^-1 mol^-1
(d) 4.366cal. K^-1 mol^-1
Answer: d

Question. If t.Gfor a reaction is negative, you infer that the change is
(a) spontaneous
(b) non-spontaneous
(c) reversible
(d) irrevrsible
(e) equilibrium
Answer: a

Question. Using the data provided, calculate the multiple bond energy (kJ mol^-1 )of a C = Cbond C₂H₂ . The energy is
(take the bond energy of a C—H bond as 350 kJ mol^-1)
2C (s)+ H₂ (g) → C₂H₂ (g); ΔH = 225 kJ mol^-1
2C(s) → 2C(g); ΔH = 1410 kJ mol^-1
H₂ (g) → 2H(g); ΔH= 330 kJ mol^-1
(a) 1165
(b) 837
(c) 865
(d) 815 
Answer: d

Question. The Gibbs energy for the decomposition of Al₂O₃ at 500°C is as follows
2/3 Al₂O₃ ➔ 4/3 Al +O₂ , Δ_rG° = + 966 kJ mol^-1 
The potential difference needed for electrolytic reduction of Al₂O₃ at 500°C is at least 
(a) 4.5 V
(b) 3.0 V
(c) 2.5 V
(d) 5.0 V
Answer: c

Question. Identify the correct statement from the following in a chemical reaction. 
(a) The entropy always increases
(b) The change in entropy along with suitable change in enthalpy decides the rate of reaction
(c) The enthalpy always decreases
(d) Both the enthalpy and the entropy remain constant 
Answer: d

Question. For an isolated system, ΔU = 0, then
(a) ΔS = 0
(b) ΔS <0
(c) ΔS > 0
(d) The values of ΔS cannot be predicted
Answer: c

Question. For the reaction at 298 K
A(g) + B(g) ⇌ C(g) + D(g) 
ΔH° = – 29.8 kcal, ΔS° = – 0.100 kcal K^-1
What is the value of ΔG° ?
(a) l
(b) 0
(c) 2
(d) 4
Answer: b

Question. During which phenomenon does entropy decrease ?
(a) Crystallisation of sucrose from its solution
(b) Melting of ice
(c) Sublimation of camphor
(d) Rusting of iron
Answer: a

Question. Among the following for spontaneity of chemical reaction there should be 
(a) decrease in entropy and increase in free energy
(b) decrease in entropy and free energy both
(c) increase in entropy and decrease in free energy
(d) increase in entropy and free energy both
Answer: c

Question. The incorrect expression an1ong the following is t.G
(a) ΔG_system / ΔS_system= – T 
(b) In 1sotherrmal process, W_reversible = – nRT ln V_f/v_i
(c) In K = ΔG° – TΔS / RT
(d) K = e –^ΔG°/RT
Answer: c

Question. Which of the following reactions define ΔG°_f ? 
(a) C(diamond) + O₂ (g) → CO₂ (g) 
(b) 1/2 H₂(g)+ 1/2 F₂(g) → HF(g)
(c) H₄P₂O7 + H₂O → 2H₃PO₄
(d) SO₂ (g) + 1/2 O₂ (g) → SO₃ (g)
Answer: b

Question. If ΔG is negative, the reaction will be 
(a) at equilibrium
(b) not possible
(c) Both (a) and (b)
(d) possible
Answer: d

Question. Which of the following processes is associated with decrease in entropy ? 
(a) Vaporisation ofa mole of water into steam at its b.p.
(b) Dissociation of a mole of common salt in water at 300K
(c) Mixing of two partially miscible liquids
(d) Crystallisation of a salt from its saturated solution
Answer: d

Question. For a particular reversible reaction at temperature T, /ΔH and ΔS were found to be both +ve. lfT_e is the temperature at equilibrium, the reaction would be spontaneous when
(a) T_e > T
(b) T > T_e 
(c) T_e is 5 times T
(d) T = T_e
Answer: b

Question. A gas expands isothermally against a constant external pressure of 1 atm from a volume of 10 dm³ to a volwne of 20 dm³ . It absorbs 800 J of thermal energy from its surroundings. The ΔU is
(a) –3121
(b) +123J
(c) –213 J
(d) + 231 J
Answer: c

Question. An ideal gas is allowed to expand both reversibly and ineversibly in an isolated system. If T_i is the mitial temperatw·e and T_f is the final temperature, which of the following statements is correct ? 
(a) (T_f)_irrev > (T_f)_rev
(b) T_f > T_i for reversible process but T_f = T_i for irreversible process
(c) (T_f)_rev = (T_f) irrev
(d) T_f = T_i for both reversible and irreversible processes
Answer: a