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Multiple Choice Questions and Answers on Class 11 Chemistry Chapter 6 Thermodynamics

(1) Standard enthalpy of vapourisation ΔHvap for water at 100oC is 40.66 kJmol-1. The internal energy of vapourisation of water at 100°C (in kJmol-1) is (Assume water vapour to behave like an ideal gas)
[A] 43.76
[B] 40.66
[C] 37.56
[D] -43.76
Answer: 37.56
(2) Which of the following salts will have maximum cooling effect when 0.5 mole of the salt is dissolved in same amount of water. Integral heat of solution at 298 K is given for each salt?
[A] KNO3 (∆H = 35.4 kJ mol-1)
[B] NaCl (∆H = 5.35 kJ mol-1)
[C] HBr (∆H = -83.3 kJ mol-1)
[D] KOH ( ∆H = -55.6 kJ mol-1)
Answer: KNO3 (∆H = 35.4 kJ mol-1)

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(3) The temperature of the system decreases in an ______.
[A] Adiabatic Compression
[B] Isothermal Expansion
[C] Isothermal Compression
[D] Adiabatic Expansion
Answer: Adiabatic Expansion
(4) A system absorb 10 kJ of heat at constant volume and its temperature rises from 270°C to 370°C. The value of ∆ U is
[A] 100 kJ
[B] 10 kJ
[C] 0 kJ
[D] 1 kJ
Answer: 10 kJ
(5) Based on the first law of thermodynamics, which one of the following is correct?
[A] For an isothermal process, q = +w
[B] For an isochoric process, ΔU = -q
[C] For an adiabatic process, ΔU = -w
[D] For a cyclic process, q = -w
Answer: For a cyclic process, q = -w
(6) The amount of the heat released when 20 ml 0.5 M NaOH is mixed with 100 ml 0.1 M HCl is x kJ. The heat of neutralization is
[A] -100 × kJ/mol
[B] -50 × kJ/mol
[C] 100 × KJ/mol
[D] 50 × kJ/mol
Answer: -100 × kJ/mol
(7) The enthalpies of combustion of carbon and carbon monoxide are -393.5 and -283.0 kJ mol-1 respectively. The enthalpy of formation of carbon monoxide is:
[A] -676 kJ
[B] 110.5 kJ
[C] -110.5 kJ
[D] 676.5 kJ
Answer: -110.5 kJ
(8) Which thermodynamic function accounts automatically for enthalpy and entropy both?
[A] Helmholtz Free Energy (A)
[B] Internal Energy (E)
[C] Work Function
[D] Gibbs Free Energy
Answer: Gibbs Free Energy
(9) The bond energy (in kcal mol-1) of a C-C single bond is approximately
[A] 1
[B] 10
[C] 83-85
[D] 1000
Answer: 83-85
(10) In which of the following process, a maximum increase in entropy is observed?
[A] Dissolution of Salt in Water
[B] Condensation of Water
[C] Sublimation of Naphthalene
[D] Melting of Ice
Answer: Sublimation of Naphthalene
(11) An ideal gas is taken around the cycle ABCA as shown in P-V diagram The next work done by the gas during the cycle is equal to:

[A] 12P1V1
[B] 6P1V1
[C] 5P1V1
[D] P1V1
Answer: 5P1V1
(12) A system absorb 10 kJ of heat at constant volume and its temperature rises from 270 C to 370 C. The value of ∆ U is
[A] 100 kJ
[B] 10 kJ
[C] 0 kJ
[D] 1 kJ
Answer: 10 kJ
(13) In a system where ∆E = -51.0 kJ, a piston expanded against a pext of 1.2 atm giving a change in volume of 32.0 L. What was the change in heat of this system?
[A] -36 kJ
[B] -13 kJ
[C] -47 kJ
[D] 24 kJ
Answer: -47 kJ
(14) Calculate the heat required to make 6.4 Kg CaC2 from CaO(s) and C(s) from the reaction: CaO(s) + 3 C(s) → CaC2(s) + CO (g) given that ∆f Ho (CaC2) = -14.2 kcal. ∆f H° (CO) = -26.4 kcal.
[A] 5624 kcal
[B] 1.11 × 104 kcal
[C] 86.24 × 10³
[D] 1100 kcal
Answer: 1.11 × 104 kcal
(15) Which of the following is true for the reaction? H2O (l) ↔ H2O (g) at 100° C and 1 atm pressure
[A] ∆S = 0
[B] ∆H = T ∆S
[C] ∆H = ∆U
[D] ∆H = 0
Answer: ∆S = 0
(16) In a reversible process the system absorbs 600 kJ heat and performs 250 kJ work on the surroundings. What is the increase in the internal energy of the system?
[A] 850 kJ
[B] 600 kJ
[C] 350 kJ
[D] 250 kJ
Answer: 350 kJ
(17) The species which by definition has ZERO standard molar enthalpy of formation at 298 K is
[A] Br2(g)
[B] Cl2(g)
[C] H2O(g)
[D] CH4(g)
Answer: Cl2(g)
(18) The enthalpy of vaporisation of a substance is 8400 J mol-1 and its boiling point is –173°C. The entropy change for vaporisation is :
[A] 84 J mol-1K-1
[B] 21 J mol-1K-1
[C] 49 J mol-1K-1
[D] 12 J mol-1K-1
Answer: 84 J mol-1K-1
(19) One mole of which of the following has the highest entropy?
[A] Liquid Nitrogen
[B] Hydrogen Gas
[C] Mercury
[D] Diamond
Answer: Hydrogen Gas
(20) Third law of thermodynamics provides a method to evaluate which property?
[A] Absolute Energy
[B] Absolute Enthalpy
[C] Absolute Entropy
[D] Absolute Free Energy
Answer: Absolute Entropy

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