MCQs on Thermodynamics

MCQs on Thermodynamics

1. What will be the value of ΔH, if the forward and reverse reactions have the same energy of activation?

(a) ΔH = ΔG = ΔS = 0

(b) ΔS = 0

(c) ΔG = 0

(d) ΔH = 0

Answer: (d)

2. What will be the entropy change (ΔS), when an ideal gas undergoes a change in the pressure from p_i to p_f isothermally?

(a)

 

(b)

 

(c)

 

(d)

 

Answer: (a)

3. Find out the relationship between x, y and z considering below three reactions

(a) y = 2z – x

(b) x = y – z

(c) x = y + z

(d) z = x + y

Answer: (c)

4. What is the molar entropy change for melting of ice at 0℃, if ΔH_f = 1.435 kcal/mol?

(a) 0.526 cal/(mol K)

(b) 5.26 cal/(mol K)

(c) 10.52 cal/(mol K)

(d) 21.04 cal/(mol K)

Answer: (b)

5. What is the function of a catalyst in a chemical reaction?

(a) decrease rate constant of reaction

(b) increases activation energy of reaction

(c) reduces enthalpy of reaction

(d) does not affect the equilibrium constant of reaction

Answer: (d)

6. What will be the work done by 3 moles of an ideal gas when it expands spontaneously in a vacuum?

(a) zero

(b) infinite

(c) 3 joules

(d) 9 joules

Answer: (a)

7. Find the temperature at which the below reaction will be in equilibrium if the enthalpy and entropy change for the reaction is 30 kJ mol^-1 and 105 J K^-1 mol^-1 respectively

Br_2(l) + Cl_2(g) → 2BrCl_(g)

(a) 273 K

(b) 300 K

(c) 450 K

(d) 285.7 K

Answer: (d)

8. Which is true for the entropy of a spontaneous reaction?

(a) ΔS_(system) – ΔS_{(surroundings)} > 0

(b) ΔS_(system) + ΔS_{(surroundings)} > 0

(c) ΔS_{(surroundings)} > 0 only

(d) ΔS_(system) > 0 only

Answer: (b)

9. An ideal gas is expanded isothermally at 300 K from 1 litre to 10 litres. Find the ΔE for this process (R = 2 cal mol^-1 K^-1)

(a) 9 L atm

(b) 1381.1 cal

(c) zero

(d) 163.7 cal

Answer: (c)

10. ΔH for the reaction N₂ + 3H₂ ⇋ 2NH₃

(a) ΔE – 2RT

(b) ΔE + 2RT

(c) ΔE – RT

(d) ΔH = RT

Answer: (a)