# MCQ | Thermochemistry

Practice Test – I

In each of the objective question, FOUR alternative(s) are given of which one or more than one is/are correct(s). Select the correct alternative(s).

Q:1. Work done in reversible isothermal process is given by

(A) $2.303 R T log\frac{V_2}{V_1}$

(B) $\frac{n R}{\gamma -1}(T_2 – T_1)$

(C) $2.303 R T log\frac{V_1}{V_2}$

(D) None

Ans: (A)

Q:2. Work done in reversible adiabatic process is given by

(A) $2.303 R T log\frac{V_1}{V_2}$

(B) None

(C) $2.303 R T log\frac{V_2}{V_1}$

(D) $\frac{n R}{\gamma -1}(T_2 – T_1)$

Ans: (B)

Q:3. Entropy change of vaporisation at constant pressure is given by

(A) $\Delta S_v = \frac{\Delta H_v}{T}$

(B) $\Delta S_v = \frac{\Delta E_v}{T}$

(C) $\Delta S_v = \frac{\Delta H_v}{\Delta T}$

(D) None

Ans: (A)

Q:4. The work done during the process when 1 mole of gas is allowed to expand freely into vaccum is

(A) 0

(B) +ve

(C) –ve

(D) Either of these

Ans: (A)

Q:5. 1 mole of an ideal gas at 25°C is subjected to expand reversibly ten times of its initial volume. The change in entropy of expansion is

(A) 19.15 JK–1 mol–1

(B) 16.15 KJ–1 mol

(C) 22.15 JK–1 mol–1

(D) None

Ans: (A)

Q:6. The entropy change for the reaction given below is

2H2(g) + O2(g) → 2H2O(l)

is … at 300 K. Standard entropies of H2(g). O2(g) and H2O9l) are 126.6, 201.20 and 68.0 JK–1 mol–1 respectively.

(A) –318.4 JK–1 mol–1

(B) 318.4  JK–1 mol–1

(C) 31.84  JK–1 mol–1

(D) None

Ans: (A)

Q:7. The enthalpy of neutralisation of the given reaction

H2SO4 + 2NaOH →Na2SO4 + 2H2O + y kcal is

(A) y kcal

(B) –y kcal

(C) + y/2 kcal

(D) –y/2 kcal

Ans: (D)

Q:8. When solute remains in equilibrium with given solvent then

(A) DHhydration = Lattice energy

(B) DHhydration < Lattice energy

(C) DHhydration > Lattice energy

(D) None

Ans: (A)

Q:9. At equilibrium condition, the value of Gibbs free energy change, ΔG is

(A) Equal to zero

(B) Greater than one

(C) Less than one

(D) Equal to one

Ans: (A)

Q:10. For spontaneous reaction the value of change of Gibbs free energy, ΔG is

(A) Negative

(B) Positive

(C) Greater than one

(D) One

Ans: (A)

Q:11. For isochoric process, the change in

(A) Volume of zero

(B) Pressure of zero

(C) Internal energy is zero

(D) None

Ans: (A)

Q:12. Which of the following is the heat of combustion ?

(A) C(graphite) + 1/2 O2(g) → CO(g) + x cal

(B) C(diamond) + O2(g) → CO2(g) + y cal

(C) C(diamond) + 1/2 O2(g) → CO(g) + z cal

(B) None

Ans: (D)

Q:13. Heat of reaction of constant p or constant v varies with temperature as given by Kirchoff’s equation is/are

(A) ΔH2 = ΔH1 + ΔCP (T2– T1)

(B) ΔE2 = ΔE1 + ΔCP (T2 – T1)

(C) H2 = H1 + DCp (T2 – T1)

(D) ΔE2 = ΔE1 + Cp (T2 – T1)

Ans: (A) (B)

Q:14. For the combustion reaction at 298 K

H2(g) + (1/2) O2(g)  → H2O (l)

Which of the following alternative(s) is/are correct

(A) ΔH = ΔE

(B) ΔH > ΔE

(C) ΔH < ΔE

(D) ΔH &  ΔE has no relation with each there

Ans: (B)

Q:15. The temperature of a 5 ml of strong acid increases by 5°C when 5 mol of a strong base is added to it. If 10 ml of each are mixed, temperature should increase by

(A) 5°C

(B) 10°C

(C) 15°C

(D) Cannot be known

Ans: (A)

Q:16. If H2(g) = 2H(g); ΔH = 104 cal, then heat of atomisation of hydrogen is

(A) 52 kcal

(B) 104 kcal

(C) 208 kcal

(D) None of these

Ans: (A)

Q:17. Given N2(g) + 3H(g) = 2NH3(g); ΔH0 = –22 kcal. The standard enthalpy of formation of NH3 gas is

(A) –11 kcal/mol

(B) 11 kcal/mol

(C) –22 kcal/mol

(D) 22 kcal/mol

Ans: (A)

Q:18. Heat of combustion of CH4, C2H4, C2H6 are –890, –1411 and –1560 kJ/mol respectively. Which has the lowest calorific fuel value in kJ/g.

(A) CH4

(B) C­2H4

(C) C­2H6

(D) All same

Ans: (B)

Q:19. ΔH for CaCO3(s) → CaO(s) + CO2(g) is 176 kJ mol–1 at 1240 K. The DE for the change is equal to

(A) 160 kJ
(B) 165.6 kJ

(C) 186.3 kJ

(D) 180.0 kJ

Ans: (B)

Q:20. Cdiamond + O2(g) → CO2(g); ΔH = –395 kJ       ..(i)

Cgraphite + O2(g) → CO2(g);    ΔH = –393.5 kJ        ..(ii)

The ΔH, when diamond is formed from graphite is

(A) –1.5 kJ

(B) +1.5 kJ

(C) +3.0 kJ

(D) –3.0 kJ

Ans: (B)

Q:21. The temperature at which the reaction,

Ag2O(s) → 2Ag(s) + (1/2) O2(g)

Is at equilibrium is …; Given ΔH = 30.5 kJ mol–1 and ΔS = 0.066 kJ K–1 mol–1

(A) 462.12 K
(B) 362.12 K

(C) 262.12 K

(D) 562.12 K

Ans: (A)

Q:22. If 50 calorie are added to a system and system does work of 30 calorie on surroundings, the change in internal energy of system is

(A) 20 cal

(B) 50 cal

(C) 40 cal

(D) 30 cal

Ans: (A)

Q:23. If S0 for H2, Cl2 and HCl are 0.13, 0.22 and 0.19 kJ K–1 mol–1 respectively. The total change in standard entropy for the reaction H2 + Cl2 → 2HCl is

(A) 30 JK–1mol–1

(B) 40 JK–1mol–1

(C) 60 JK–1mol–1

(D) 20 JK–1mol–1

Ans: (A)

Q:24. If H+ + OH → H2O + 13.7 kcal then the heat of neutralisation for complete neutralisation of 1 mole of H2SO4 by base will be

(A) 13.7 kcal

(B) 27.4 kcal

(C) 6.85 kcal

(D) 3.425 kcal

Ans: (B)

Q:25. Heat evolved in the reaction H2 + Cl2 → 2HCl is 182 kJ. Bond energies of H – H and Cl – Cl are 430 and 242 kJ/mol respectively. The H – Cl bond energy is

(A) 245 kJ moil–1

(B) 427 kJ mol–1

(C) 336 kJ mol–1

(D) 154 kJ mol–1

Ans: (A)

Q:26. Heat or formation of H2O(g) at 1 atm and 25°C is –243 kJ.  ΔE for the reaction H2(g) + 30 JK–1mol–1  (1/2)O(g) → H2O(g) at 25°C is

(A) 241.8 kJ

(B) –241.8 kJ

(C) –243 kJ

(D) 243 kJ

Ans: (B)

Q:27. The H – H bond energy is 430 kJ mol–1 and Cl – Cl bond energy is 240 kJ mol–1. DH for HCl is –90 kJ. The H – Cl bond energy is about.

(A) 425 kJ mol–1

(B) 213 kJ mol–1

(C) 360 kJ mol–1

(D) 180 kJ mol–1

Ans: (A)

Q:28. The enthalpies of combustion of carbon and carbon monoxide are –390 kJ and –278 kJ respectively. The enthalpy of formation of CO in kJ is

(A) 668

(B) 112

(C) –112

(D) –668

Ans: (C)

Q:29. Under the same conditions how many ml of 1 M KOH and 0.5 M H2SO4 solutions, respectively when mixed for a total volume of 100 ml produce the highest rise in temperature

(A) 67 : 33

(B) 33 : 67

(C) 40 : 60

(D) 50 : 50

Ans: (D)

Q:30. ΔH of sublimation of a solid is equal to

(A) ΔHfusion + ΔHcondensation

(B) ΔHcondensation + ΔHsublimation

(C) ΔHcondensation – ΔHfusion

(D) ΔHvaporisation + ΔHfusion

Ans: (D)

Q:31. The expression, ΔHsubo = ΔHfuso + ΔHvapo is true at all

(A)Temperatures

(B) Pressures

(C) Temperatures & pressures

(D) Temperature & 1 atm pressure conditions

Ans: (D)

Q:32. According to the equation

C6H6(l) +15/2 O2(g) → 3H2O (l) + 6 CO2(g)

ΔH = –3264.4 kJ mol–1, the energy evolved when 7.8 gm of benzene is burnt in air will be

(A) 163.22 kJ/mol–1

(B) 326.4 kJ/mol

(C) 32.64 kJ/mol–1

(D) 3.264 kJ/mol

Ans: (B)

Q:33. The product of combustion of an aliphatic thiol (RSH) at 298 K are

(A) CO2(g), H2O(g), & SO2(g)

(B) CO2(g), H2O(g), H2O(l) & SO2(g)

(C) CO2(l), H­2O(l) & SO2(g)

(D) CO2(g), H2O(l), SO2(l)

Ans: (A)

Q:34. Given ΔHioniz (HCN) = 45.2 kJ mol–1 & ΔHioniz (CH3COOH) = 2.1 kJ/mol

(A)pKa (HCN) = pKa (CH3COOH)

(B) pKa (HCN) > pKa (CH3COOH)

(C)pKa (HCN) < pKa (CH3COOH)

(D)pKa (HCN) = (45.17/2.07) pKa (CH3COOH)

Ans: (B)

Q:35. AB, A2 and B2 are diatomic molecules. If the bond enthalpies of A2, AB & B2 are `in the ratio 1:1:0.5 and enthalpy of formation of AB from A2 and B2 –100 kJ/mol–1. What is the bond enthalpy of A2?

(A) 400 kJ/mol

(B) 200 kJ/mol

(C) 100 kJ/mol

(D) 300 kJ/mol

Ans: (A)

Q:36. Which of the following corresponds to the definition of enthalpy of formation at 298 K?

(A)C(graphite) + 2H2(g) + 1/2 O2(l) CH3OH(g)

(B)C(diamond) + 2H2(g) + 1/2 O2(g) CH3OH (l)

(C)2C(graphite) + 4H2(g) + 4H2(g) + O2(g) 2CH3OH (l)

(D)C(graphite) + 2H2(g) + 1/2 O2(g) CH3OH(l)

Ans: (D)

Q:37. In which case, a reaction is possible at any temperature ?

(A) ΔH < 0, ΔS > 0

(B) ΔH < 0, ΔS < 0

(C) ΔH > 0, ΔS > 0

(D) None

Ans: (A)

Q:38. Which of the following has impossibilities of reaction of any temperature ?

(A) ΔH > 0, ΔS < 0

(B) ΔH > 0, ΔS > 0

(C) ΔH < 0, ΔS < 0

(D) None

Ans: (B)

Q:39. The temperature of 5 ml of a strong acid increases by 5° C when 5 ml of a strong base is added to it. If 10 ml of each is mixed, temperature should increase by

(A) 5° C

(B) 10° C

(C) 15° C

(D) Cannot be known

Ans: (A)

Q:40. Identify the intensive quantities from the following:

(A) Enthalpy

(B) Temperature

(C) Volume

(D) Refractive index