Entropy MCQs

Entropy MCQs

Entropy quantifies the degree of randomness or disorder within a system and is represented by the thermodynamic function S. Greater entropy indicates more disorder in an isolated system. In a chemical reaction, changes in entropy reflect the rearrangement of atoms from reactants to products, with entropy increasing if the product’s structure is more disordered. Additionally, adding heat to a system raises randomness and, consequently, entropy. The change in entropy (ΔS) is greater at lower temperatures compared to higher temperatures when the same amount of heat is added.

For which of the following conditions a reaction will be spontaneous at all temperatures?

(a) ΔH < 0 and ΔS < 0

(b) ΔH < 0 and ΔS = 0

(c) ΔH < 0 and ΔS > 0
(d) both (b) and (c)

For spontaneous adsorption of gas

(a) ΔS is negative so ΔH should be highly positive
(b) ΔS is negative so ΔH should be highly negative
(c) ΔS is positive so ΔH should also be highly positive
(d) ΔS is positive so ΔH should be negative

Which of the following is the correct criterion for a spontaneous process?

(a) ΔSsystem – ΔSsurroundings > 0
(b) ΔSsurroundings > 0 only
(c) ΔSsystem + ΔSsurroundings > 0
(d) ΔSsystem > 0 only

At which of the following temperatures will the reaction Br2 (l) + Cl2 (g) → 2BrCl(g) be at equilibrium if ΔH = 30 kJ mol⁻¹ and ΔS = 170 J K⁻¹ mol⁻¹?

(a) 450 K
(b) 300 K
(c) 273 K
(d) 285.7 K

At which of the following temperatures will the reaction C(graphite) + CO2 (g) → 2CO(g) occur spontaneously if ΔH = 170 kJ and ΔS = 170 J K⁻¹?

(a) 710 K
(b) 1110 K
(c) 910 K
(d) 510 K

Which of the following is true for the entropy of an isolated system?

(a) It can never increase
(b) It can never decrease
(c) It can never be zero
(d) None of the above

Which of the following is correct for the net entropy change in an irreversible process?

(a) It is positive
(b) It is negative
(c) It is zero
(d) All of the above

For a spontaneous reaction

(a) ΔS must be negative
(b) (ΔH – TΔS) must be negative
(c) ΔH must be negative
(d) (ΔH + TΔS) must be negative

Calculate ΔG for the reaction X2O4 (l) → 2XO2 (g) if ΔU = 2.1 kcal and ΔS = 20 cal K⁻¹ at 300°K.

(a) – 9.3 kcal
(b) – 2.7 kcal
(c) 2.7 kcal
(d) 9.3 kcal

What is the unit of entropy?

(a) J mol⁻¹
(b) J K mol⁻¹
(c) J⁻¹ K⁻¹ mol⁻¹
(d) J K⁻¹ mol⁻¹