The enthalpy of vaporization of benzene is +35.3 kJ/mol at its boiling point of 80°C. The entropy change in the transition of vapour to liquid at its boiling point is

1. -100

2. +100

3. +342

4. -342

Subtopic:  Enthalpy & Internal energy |
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A piece of metal weighing 100 g is heated to 80°C  and dropped into 1 kg of cold water in an insulated container at 15°C. If the final temperature of the water in the container is 15.69°C, the specific heat of metal in J/g.°C is

1. 0.38

2. 0.24

3. 0.45

4. 0.13

Subtopic:  Enthalpy & Internal energy |
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The maximum work (in kJ mol-1) that can be derived from complete combustion of 1 mol of CO at 298 K and 1 atm is

[standard enthalpy of combustion of CO=-283.0 kJ mol-1; standard molar entropies at 298 K: SO2=205.1 J mol-1, SCO=197.7 J mol-1SCO2=213.7 J mol-1]

1. - 257

2. 227

3. 257

4. 127

Subtopic:  Gibbs Energy Change |
 53%
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An ideal gas is taken through the cycle ABC as shown in figure, if net heat supplied to the gas in the cycle is 5 J, the work done by the gas in the process CA is

1. -5 J

2. -10 J

3. -15 J

4. -20 J

Subtopic:  2nd & 3rd Law of Thermodynamics |
 59%
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The amount of heat required to raise the temperature of 1 mole diatomic gas by 1°C at constant pressure is 60 cal. The amount of heat which goes as internal energy of the gas is nearly

1. 60 cal

2. 30 cal

3. 42.6 cal

4. 49.8 cal

Subtopic:  Cp & Cv |
 53%
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The reaction 3O2(g)2O3(g) is endothermic. What can be concluded about the average energy per bond in O2 and O3?

1. The average energy per bond in O2 is greater than that in O3

2. The average energy per bond in O2 is less than that in O3

3. The average energy per bond in O2 is equal to that is O3

4. Number conclusion can be drawn about the average bond energies from this information done

Subtopic:  Enthalpy & Internal energy |
 60%
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4.8 g of C(diamond) on complete combustion evolves 1584 kJ of heat. The standard heat of formation gaseous carbon is 725 kJ/mol. The energy required for the process

(i) C(graphite)C(gas)

(ii) C(diamond)C(gas)are

1. 725, 727

2. 727, 725

3. 725, 723

4. None of these

Subtopic:  Hess's Law |
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The enthalpies of the following reactions are shown alongwith.

12H2g+12O2gOHg ; H=42.09 kJ mol-1
H2g2Hg;                      H=435.89 kJ mol-1
O2g2Og;                      H=495.05 kJ mol-1

Calculate the O-H bond energies for the hydroxyl radical.

1. 223.18 kJ mol-1

2. 423.38 kJ mol-1

3. 513.28 kJ mol-1

4. 113.38 kJ mol-1

Subtopic:  Thermochemistry |
 76%
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The enthalpies of formation of CO2(g) and CO(g) at 298 K are in the ratio 2.56 : 1. For the reaction,

CO2(g)+C(s)2CO(g), H=177.5kJ,
Hf of CO(g)  is-

1. -150.6 kJ mol-1

2. -113.78 kJ mol-1

3. -130.2 kJ mol-1

4. -141.8 kJ mol-1

Subtopic:  Enthalpy & Internal energy |
 61%
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The bond energies ofCC, C-H, H-H and C=C are 198, 98, 103 and145 kcal respectively. The enthalpy change of the reaction HCCH+H2C2H4 is:

1. 48 kcal

2. 96 kcal

3. -40 kcal

4. -152 kcal

Subtopic:  Enthalpy & Internal energy |
 76%
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