The occurrence of a reaction is impossible if:

1. ΔH is +ve ; ΔS is also + ve but ΔH < TΔS

2. ΔH is – ve ; ΔS is also – ve but ΔH > TΔS

3. ΔH is – ve ; ΔS is + ve

4. ΔH is + ve ; ΔS is – ve

The enthalpy and entropy change for a chemical reaction are

–2.5 × 10³ cal and 7.4 cal deg^–1 respectively.  Predict the reaction at 298 K is

1. Spontaneous

2. Reversible

3. Irreversible

4. Non-spontaneous

Which of the following is true for the reaction $H_{2}O\left(l\right)\underset{}{\overset{}{\rightleftharpoons }}{H}_{2}O\left(g\right)$ at 100°C and 1 atmosphere

1. ΔE = 0

2. ΔH = 0

3. ΔH = ΔE

4. ΔH = TΔS

The enthalpy of vapourization water is 386 kJ. What is the entropy of water

(1) 0.5 kJ

(2) 1.03 kJ

(3) 1.5 kJ

(4) 22.05 kJ

Mark the correct statement regarding entropy.

An engine operating between 150°C and 25°C takes 500 J heat from a higher temperature reservoir if there are no frictional losses, then work done by engine is [MH CET 1999]

(1) 147.7 J

(2) 157.75 J

(3) 165.85 J

(4) 169.95 J

The standard entropies of CO₂(g), C(s) and O₂(g) are 213.5, 5.690 and 205 JK^–1 respectively. The standard entropy of formation of CO₂(g) is

(1) 1.86 JK^–1

(2) 1.96 JK^–1

(3) 2.81 JK^–1

(4) 2.86 JK^–1

Equal volumes of monoatomic and diatomic gases at same initial temperature and pressure are mixed. The ratio of specific heats of the mixture (C_p/C_v) will be [AFMC 2002]

(1) 1

(2) 2

(3) 1.67

(4) 1.5

The unit of entropy is -

1. J mol^–1

2. JK mol^–1

3. J mol^–1 K^–1

4. J^–1 K^–1 mol^–1

The entropy changed involved in the conversion of 1 mole of liquid water at 373 K to vapour at the same temperature will be $[\Delta H_{\text{vap}}=2.257kJ/gm]$ [MP PET 2002]

(1) 0.119 kJ

(2) 0.109 kJ

(3) 0.129 kJ

(4) 0.120 kJ