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

Subtopic:  Gibbs Energy Change |
 84%
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Which of the following is true for the reaction H2O(l)H2O(g) at 100°C and 1 atmosphere

1. ΔE = 0

2. ΔH = 0

3. ΔH = ΔE

4. ΔH = TΔS

Subtopic:  Gibbs Energy Change |
 68%
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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

Subtopic:  Spontaneity & Entropy |
 78%
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Identify the correct statement regarding entropy [CBSE PMT 1998; BHU 2001]

1. At 0°C, the entropy of a perfectly crystalline substance is taken to be zero

2. At absolute zero temperature, the entropy of a perfectly crystalline substance is +ve

3. At absolute zero temperature, the entropy of all crystalline substances is taken to be zero

4. At absolute zero temperature, the entropy of a perfectly crystalline substance is taken to be zero

Subtopic:  Spontaneity & Entropy |
 62%
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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

Subtopic:  First Law of Thermodynamics |
 53%
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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

Subtopic:  Thermochemistry |
 76%
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Equal volumes of monoatomic and diatomic gases at same initial temperature and pressure are mixed. The ratio of specific heats of the mixture (Cp/Cv) will be [AFMC 2002]

(1) 1

(2) 2

(3) 1.67

(4) 1.5

Subtopic:  Cp & Cv |
 51%
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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

Subtopic:  Spontaneity & Entropy |
 85%
From NCERT
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The entropy changed involved in the conversion of 1 mole of liquid water at 373 K to vapour at the same temperature will be [ΔHvap=2.257kJ/gm] [MP PET 2002]

(1) 0.119 kJ

(2) 0.109 kJ

(3) 0.129 kJ

(4) 0.120 kJ

Subtopic:  Spontaneity & Entropy |
 74%
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When a liquid boils, there is [JIPMER 2002]

(1) An increase in entropy

(2) A decrease in entropy

(3) An increase in heat of vaporization

(4) An increase in free energy

Subtopic:  Spontaneity & Entropy |
 87%
From NCERT
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