CBSE Class 11 Chemistry Thermodynamics MCQs Set B

Question: In an endothermic reaction, the value of ΔH is
a) negative
b) positive
c) zero
d) constant. 
Answer: b

Question: One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1 litre to 10 litres. The ΔE 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 
Answer: b

Question: 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 
Answer: a

Question: In which case change in entropy is negative?
a) 2H_(g) → H_2(g)
b) Evaporation of water
c) Expansion of a gas at constant temperature
d) Sublimation of solid to gas 
Answer: a

Question: If the bond energies of H–H, Br–Br, and H–Br are 433, 192 and 364 kJ mol^–1 respectively, the ΔH° for the reaction H_2(g) + Br_2(g) → 2HBr_(g) is
a) –261 kJ
b) +103 kJ
c) +261 kJ
d) –103 kJ
Answer: d

Question: A reaction occurs spontaneously if
a) TΔS < ΔH and both ΔH and ΔS are +ve
b) TΔS > ΔH and DH is +ve and ΔS is –ve
c) TΔS > ΔH and both ΔH and ΔS are +ve
d) TΔS = ΔH and both ΔH and ΔS are +ve 
Answer: c

Question: If the enthalpy change for the transition of liquid water to steam is 30 kJ mol^–1 at 27°C, the entropy change for the process would be
a) 10 J mol^–1 K^–1
b) 1.0 J mol^–1 K^–1
c) 0.1 J mol^–1 K^–1
d) 100 J mol^–1 K^–1
Answer: d

Question: Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE?
a) 2CO_(g) + O_2(g) → 2CO_2(g)
b) H_2(g) + Br_2(g) → 2HBr_(g)
c) C(s) + 2H₂O_(g) → 2H₂(g) + CO_2(g)
d) PCl_5(g) → PCl_3(g) + Cl_2(g) 
Answer: b

Question: The enthalpy and entropy change for the reaction: Br_2(l) + Cl_2(g) → 2BrCl_(g) are 30 kJ mol^–1 and 10⁵ J K^–1 mol^–1 respectively. The temperature at which the reaction will be in equilibrium is
a) 300 K
b) 285.7 K
c) 273 K
d) 450 K 
Answer: b

Question: For which one of the following equations is DH°reaction equal to ΔH°f for the product?
a) N_2(g) + O_3(g) → N₂O_3(g)
b) CH4_(g) + 2Cl_2(g) → CH₂Cl_2(l) + 2HCl_(g)
c) Xe_(g) + 2F_2(g) → XeF_4(g)
d) 2CO_(g) + O2_(g) → 2CO_2(g) 
Answer: c

Question: Heat required to raise the temperature of I mole of a substance by 1° is called
a) specific heat
b) molar beat capacity
c) water equivalent
d) specific gravity
Answer: b

Question: In which of the following process, maximum increase in entropy is observed ? 
a) Melting of ice
b) Sublimation of naphthalene
c) Condensation of water
d) Dissolution of salt in water 
Answer: b 

Question: Hess's law states that 
a) the standard enthalpy ofan overall reaction is the sum of the enthalpy changes in individual reactions
b) enthalpy of formation of a compound is same as the enthalpy of decomposition of the compound into constituent elements, but with opposite sign
c) at constant temperature the pressure of a gas is inversely proportional to its volume
d) the mass of a gas dissolved per litre of a solvent is proportional to the pressure of the gas in equilibrium with the solution.
Answer: a

Question: At 298 K the entropy of rhombic sulphur is 32.04 J/mol K and that of monoclinic sulphur is 32.68 J/mol K. The heat of their combustion are respectively -298246 and -297948 J mol^-1 .ΔG for the reactions; S_rhombic → S_monoclinic will be 
a) 107.28 J
b) 10.728 J
c) 107.28 kJ
d) 10728 J
Answer: a 

Question: The bond dissociation energies of X₂, Y₂ and XY are in the ratio of 1 : 0.5 : 1. DH for the formation of XY is –200 kJ mol^–1. The bond dissociation energy of X₂ will be
a) 200 kJ mol^–1
b) 100 kJ mol^–1
c) 800 kJ mol^–1
d) 400 kJ mol^–1
Answer: c

Question: Based on the first law of thermodynamics, which one of the following is correct ? 
a) For an isochoric process= ΔE = - Q
b) For an adiabatic process = ΔE = - W
c) For an isothermal process = Q = + W
d) For a cyclic process = Q = - W
Answer: d

Question: 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
Answer: a

Question: Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction?
a) Exothermic and increasing disorder
b) Exothermic and decreasing disorder
c) Endothermic and increasing disorder
d) Endothermic and decreasing disorder 
Answer: a

Question: If ΔH is the change in enthalpy and ΔE, the change in internal energy accompanying a gaseous reaction, then
a) ΔH is always greater than ΔE
b) ΔH < ΔE only if the number of moles of the products is greater than the number of moles of the reactants
c) ΔH is always less than ΔE
d) ΔH < ΔE only if the number of moles of products is less than the number of moles of the reactants.
Answer: d

Question: Bond dissociation enthalpy of H₂, Cl₂ and HCl are 434, 242 and 431 kJ mol^–1 respectively. Enthalpy of formation of HCl is
a) –93 kJ mol^–1
b) 245 kJ mol^–1
c) 93 kJ mol^–1
d) –245 kJ mol
Answer: a

Question: Which is an extensive property?
a) Temperature
b) Chemical potential
c) Gibb's free energy
d) Molar volume
Answer: c

Question: Entropy of the universe is
a) constant
b) zero
c) continuously decreasing
d) continuously increasingVVVD
Answer: d

Question: Standard enthalpy and standard entropy changes for the oxidation of ammonia at 298 K are –382.64 kJ mol^–1 and –145.6 J mol^–1, respectively. Standard Gibbs’ energy change for he same reaction at 298 K is
a) – 221.1 kJ mol^–1
b) – 339.3 kJ mol^–1
c) – 439.3 kJ mol^–1
d) – 523.2 kJ mol^–1
Answer: b

Question: How many joules of beat are absorbed when 70. O g of water is completely vaporised at its boiling point ? ( L_v = 2260 kJ/kg) 
a) 23352
b) 7000
c) 15813
d) 158200 
Answer: d

Question: Equal volumes of two monatomic gases, A and B at same temperature and pressure are mixed. The ratio of specific heats (CP/CV) of the mixture will be
a) 0.83
b) 1.50
c) 3.3
d) 1.67
Answer: d

Question: A reaction having equal energies of activation for forward and reverse reactions has
a) ΔH = 0
b) ΔH = DG = ΔS = 0
c) ΔS = 0
d) ΔG = 0 
Answer: a

Question: For a reversible reaction,X(g) + 3Y(g) ⇌ 2Z(g); ΔH = - 40 kJ, the standard entropies of X, Y and Z are 60, 40 and 50 JK^-1 mol^-1 respectively. The temperature at which the above reaction attains equilibrium is about
a) 400 K
b) 500 K
c) 273 K
d) 373 K
Answer: b

Question: During isothermal expansion of an ideal gas, its
a) internal energy increases
b) enthalpy decreases
c) enthalpy remains unaffected
d) enthalpy reduces to zero.
Answer: c

Question: Under isothermal conditions, a gas at 300 K expands from 0.1 L to 0.25 L against 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
Answer: b

Question: An ideal gas expands isothermally from 10^–3 m³ to 10^–2 m³ at 300 K against a constant pressure of 10⁵ N m^–2. The work done on the gas is
a) +270 kJ
b) –900 J
c) +900 kJ
d) –900 kJ
Answer: b

Question: When 1 mol of gas is heated at constant volume temperature is raised from 298 to 308 K. Heat supplied to the gas is 500 J. Then which statement is correct?
a) q = w = 500 J, ΔE = 0
b) q = ΔE = 500 J, w = 0
c) q = w = 500 J,ΔE = 0
d) ΔE = 0, q = w = –500 J
Answer: b

Question: Which of the following statements is correct for the spontaneous adsorption of a gas?
a) ΔS is negative and, therefore ΔH should be highly positive.
b) ΔS is negative and therefore, ΔH should be highly negative.
c) ΔS is positive and therefore, ΔH should be negative.
d) ΔS is positive and therefore, ΔH should also be highly positive. 
Answer: b

Question: What will be the temperature at which
ΔG = -5.2kJ mol^-1, ΔH = 145.6 kJ mol^-1 and
ΔS = 216JK^-1 mol^-1 for a chemical reaction?
a) 650 K
b) 425°C 
c) 525 K
d) 625°C
Answer: b

Question: For a given reaction, ΔH = 35.5 kJ mol^–1 and DS = 83.6 J K^–1 mol^–1. The reaction is spontaneous at (Assume that ΔH and ΔS do not vary with temperature.)
a) T > 425 K
b) all temperatures
c) T > 298 K
d) T < 425 K
Answer: a

Question: For vaporization of water at 1 atmospheric pressure, the values of ΔH and ΔS are 40.63 kJ mol^–1 and 108.8 J K^–1 mol^–1, respectively. The temperature when Gibbs’ energy change ΔG) for this transformation will be zero, is
a) 273.4 K
b) 393.4 K
c) 373.4 K
d) 293.4 K 
Answer: c

Question: For a reaction ΔH = (+3 kJ),ΔS = (+ l0 J/K) beyond which temperature this reaction will be spontaneous ?
a) 300 K
b) 200 K
c) 273 K
d) 373 K
Answer: a 

Question: Which of the following is correct option for free expansion of an ideal gas under adiabatic condition?
a) q = 0, ΔT ≠ 0, w = 0
b) q ≠ 0, ΔT = 0, w = 0
c) q = 0, ΔT = 0, w = 0
d) q = 0, ΔT < 0, w ≠ 0
Answer: c

Question: The heat of combustion of carbon to CO₂ is –393.5 kJ/mol. The heat released upon formation of 35.2 g of CO₂ from carbon and oxygen gas is None
a) + 315 kJ
b) – 630 kJ
c) – 3.15 kJ
d) – 315 kJ
Answer: c

Question: The correct thermodynamic conditions for the spontaneous reaction at all temperatures is
a) ΔH < 0 and ΔS > 0
b) ΔH < 0 and ΔS < 0
c) ΔH < 0 and ΔS = 0
d) ΔH > 0 and ΔS < 0
Answer: a

Question: Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be
a) infinite
b) 3 Joules
c) 9 Joules
d) zero.
Answer: d