# Thermodynamics is not concerned about: 1. Energy changes involved in a chemical reaction. 2. The extent to which a chemical reaction proceeds. 3. The rate at which a reaction proceeds. 4. The feasibility of a chemical reaction.

Subtopic:  Thermodynamics' Properties and process |
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If for a certain reaction ${∆}_{r}H$ is 30 kJ mol–1 at 450 K, the value of ${∆}_{r}S$ (in JK–1 mol–1) for which the same reaction will be spontaneous at the same temperature is:

1. 70

2. –33

3. 33

4. –70

Subtopic:  Spontaneity & Entropy |
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NEET - 2020
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Identify the correct statement regarding entropy:

 1 At absolute zero of temperature, the entropy of all crystalline substances is taken to be zero 2 At absolute zero of temperature, the entropy of a perfectly crystalline substance is +ve 3 At absolute zero of temperature, the entropy of a perfectly crystalline substance is taken to be zero 4 At 0 °C , the entropy of a perfectly crystalline substance is taken to be zero
Subtopic:  2nd & 3rd Law of Thermodynamics |
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AIPMT - 1998
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When 1 mol gas is heated at constant volume, the temperature is raised from 298 to 308 K. Heat supplied to the gas is 500 J. The correct statement among the following is:
1.  q = w = 500 J, ∆U = 0
2.  q = ∆U = 500 J, w = 0
3.  q = w = 500 J, ∆U = 0
4.  ∆U = 0, q = w = – 500 J

Subtopic:  First Law of Thermodynamics |
86%
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AIPMT - 2001
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Match the item in column I and in column II.

 Column I Column II a. No heat is absorbed by the system from the surroundings, but work (w) is done on the system. i. ∆U = q – w, closed system. b. No work is done on the system, but q amount of heat is taken out from the system and given to the surroundings. ii. ∆U = wad, a wall is adiabatic. c. w amount of work is done by the system and q amount of heat is supplied to the system. iii. ∆U  = –q, thermally conducting walls.

 1 a = i; b = ii; c = iii 2 a = ii; b = i; c = iii 3 a = ii; b = iii; c = i 4 a = iii; b = ii; c = i
Subtopic:  First Law of Thermodynamics |
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Two litres of an ideal gas at a pressure of 10 atm expands isothermally at 25 °C into a vacuum until its total volume is 10 litres. The amount of heat absorbed during expansion is:

1. 80 J

2. -80 J

3. Zero

4. 50 J

Subtopic:  First Law of Thermodynamics |
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If water vapour is assumed to be a perfect gas, molar enthalpy change for vapourisation of 1 mol of water at 1 bar and 100°C is 41kJ mol–1. The internal energy change, when 1 mol of water is vapourised at 1 bar pressure and 100°C is:

1. 35.5 kJ mol–1

2. 37.9 kJ mol–1

3.  41 kJ mol–1

4. 44.2 kJ mol–1

Subtopic:  Enthalpy & Internal energy |
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A swimmer coming out from a pool is covered with a film of water weighing about 18g. The internal energy of vaporization at 298K. is-

vap H for water at 298K= 44.01kJ mol–1

1. 38.63 kJ
2. 43.82 J
3. 41.53 kJ
4. 40.33 J



Subtopic:  Enthalpy & Internal energy |
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The combustion of one mole of benzene takes place at 298 K and 1 atm. After combustion, CO2(g) and H2O (l)
are produced and 3267.0 kJ of heat is liberated.
The standard enthalpy of formation,
fH of benzene is:
(Standard enthalpies of formation of CO
2(g) and  are –393.5 kJ mol–1 and – 285.83 kJ mol–1 respectively.)

1. 54. 24 kJ mol-1
2. 48. 51 kJ mol-1
3. 66. 11 kJ mol-1
4. 15. 21 kJ mol-1
${}^{}$

Subtopic:  Hess's Law |
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For the oxidation of iron,

4Fe(s) + 3O2 (g) →  2Fe2O3 (s)
entropy change is -549.4 JK-1 mol-1 at 298 K.

(${∆}_{r}{H}^{\Theta }$ for this reaction is )

The reaction is:

1. Spontaneous reaction

2. Non-spontaneous reaction

3. Reaction is an equilibrium

4. Cannot predict

Subtopic:  Spontaneity & Entropy |
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