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 |
 63%
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Two litres of an ideal gas at a pressure of 10 atm expands isothermally at 25 °C against a constant external pressure of 1 atm until its total volume is 10 litres. The amount of heat absorbed during expansion is-

1. 80 atm L

2. -80 atm L

3. -8 atm L

4. 8 atm L

 

.

Subtopic:  First Law of Thermodynamics |
From NCERT
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Two litres of 1 mol 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:
(Given: log 5 = 0.699)

1. 51. 39 atm L

2. 39.36 atm L

3. 37. 34 atm ml

4. 26. 49 atm L

Subtopic:  First Law of Thermodynamics |
 59%
From NCERT
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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 |
 58%
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1g of graphite is burnt in a bomb calorimeter in excess of oxygen at 298 K and 1 atmospheric pressure according to the equation

C (graphite) + O2(g) → CO2(g)

During the reaction, the temperature rises from 298 K to 299 K. If the heat capacity of the bomb calorimeter is 20.7kJ/K, the enthalpy change for the above reaction at 298 K and 1 atm is-

1. – 2.48 ×102 kJ mol–1

2. – 3.45 ×102 kJ mol–1

3. – 1.65 ×102 kJ mol–1

4. – 1.88 ×102 kJ mol–1

Subtopic:  Enthalpy & Internal energy |
 54%
From NCERT
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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 |
 68%
From NCERT
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Assuming the water vapour to be a perfect gas. When 1 mol of water at 100°C and 1 bar pressure is converted to ice at 0°C, the change in internal energy is-

(The enthalpy of fusion of ice = 6.00 kJ mol-1 , heat capacity of water = 4.2 J/g°C)

1. 13.56 kJ mol-1

2. -12.16 kJ mol-1

3. -13.56 kJ mol-1

4. 12.16 kJ mol-1

Subtopic:  Thermochemistry |
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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 H2O (l) 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 |
 68%
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The incorrect statement(s) among the following statements is/are -

i. When liquid crystallizes into a solid, entropy increases.
ii. When the temperature of a crystalline solid is raised from 0 K to 115 K then entropy increases.
iii. 2 NaHCO3 (s) →Na2CO(s) +CO2(g)+H2O(g); Entropy  increases.
iv. H2(g)→2H(g) ; Entropy  decreases.


1. (i), (iv)
2. (ii), (iv)
3. (iii), (iv)
4. (i), (iii)

Subtopic:  Spontaneity & Entropy |
 82%
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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.

(rHΘ for this reaction is -1648 × 103 J mol-1)

The reaction is-

1. Spontaneous reaction

2. Non-spontaneous reaction

3. Reaction is an equilibrium

4. Cannot predict

Subtopic:  Spontaneity & Entropy |
 75%
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