﻿ Medical Entrance Exam Question and Answers | Thermodynamics - Zigya

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# Thermodynamics

#### Multiple Choice Questions

1.

Which of the following statements is correct for a reversible process in a state of equilibrium?

• ΔG = -2.303RT log K
• ΔG = 2.303RT log K

• ΔG0 = -2.303RT log K

• ΔG0 = -2.303RT log K

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2.

A reaction having equal energies of activation for forward and reverse reactions has

• ΔS =0
• ΔG =0
• ΔH = 0
• ΔH = 0
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3.

In which of the following reactions, standard reaction entropy changes (ΔSo) is positive and standard Gibb's energy change (ΔGo) decreases sharply with increasing temperature?

• C (graphite) +1/2 O2 (g) → CO (g)

• CO (g) +1/2 (g) → CO2 (g)

• Mg(s)  +1/2O2 (g) → MgO (s)

• Mg(s)  +1/2O2 (g) → MgO (s)

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4.

The enthalpy of fusion of water is 1.435 Kcal/mol. The molar entropy change for the melting of ice of at 0o C is

• 10.52 cal/(mol K)

• 21.04 cal/(mol K)

• 5.260 cal/ (mol K)

• 5.260 cal/ (mol K)

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5.

Standard enthalpy of vaporisation ΔvapHθ for water for water at 100oC is 40.66 kJ mol-1. The internal energy of vaporisation of water at 100o C (in KJ mol-1) is

(Assume water vapour to behave like an ideal gas.)

• +37.56

• -43.76

• +43.76

• +43.76

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6.

If the enthalpy change for the transition of liquid water to steam is 30kJ mol-1 at 27oC, the entropy change for the process would be.

• 1.0 J mol- K-1

• 0.1 J mol-1 K-1

• 100 J  mol-1 K-1

• 10 J mol-1 K-1

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7.

Which of the following is the correct option for free expansion of an ideal gas under an adiabatic condition?

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8.

Enthalpy change for the reaction,

4H (g) → 2H2 (g) is - 869.6 kJ

The dissociation energy of H - H bond is

• -869.6 kJ

• +434.8 kJ

• +217.4 kJ

• +217.4 kJ

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9.

The heat of combustion of carbon to CO2 is -395.5 kJ/mol. The heat released upon the formation of 35.2 g CO2 from carbon and oxygen gas is

• -315 kJ

• +315 kJ

• -630 kJ

• -630 kJ

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10.

The formation of the oxide ion O2- (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below,

Thus, the process of formation of O2- in the gas phase is unfavourable even though O2- is isoelectronic with neon. It is due to the fact that

• electron repulsion outweighs the stability gained by achieving a noble gas configuration

• O- ion has comparatively smaller size that oxygen atom

• oxygen is more electronegative

• oxygen is more electronegative

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