N2 + 3 H2  2NH3 ; rH° = -92.4 kJ mol-1. The standard enthalpy of formation of NH3 gas in the above reaction would be-

1. -92.4 J (mol)-1 2. -46.2 kJ (mol)-1
3. +46.2 J (mol)-1 4. +92.4 kJ (mol)-1


Subtopic:  Thermochemistry |
 81%
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The standard enthalpy of the formation of CH3OH(l)  from the following data is:

\(\small{\mathrm{CH}_3 \mathrm{OH}_{(l)}+\frac{3}{2} \mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{CO}_2(\mathrm{g})+2 \mathrm{H}_2 \mathrm{O}_{(l)} \text {; }}\)
\( \Delta_{\mathrm{r}} \mathrm{H}^{\circ}=-726 \mathrm{~kJ} \mathrm{~mol}{ }^{-1}\)
\(\small{\mathrm{C}(\mathrm{s})+\mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{CO}_2(\mathrm{g}) \text {; } }\)
\(\Delta_{\mathrm{c}} \mathrm{H}^{\circ}=-393 \mathrm{~kJ} \mathrm{~mol}{ }^{-1}\)
\(\small{\mathrm{H}_{2(\mathrm{g})}+\frac{1}{2} \mathrm{O}_{2(\mathrm{g})} \rightarrow \mathrm{H}_2 \mathrm{O}_{(l)} \text {; } } \)
\(\Delta_{\mathrm{f}} \mathrm{H}^{\circ}=-286 \mathrm{~kJ} \mathrm{~mol}^{-1}\)
 
1. −239 kJ mol−1 2. +239 kJ mol−1
3. −47 kJ mol−1 4. +47 kJ mol−1
Subtopic:  Thermochemistry |
 61%
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vapH° (CCl4) = 30.5 kJ mol-1
fH° (CCl4) = - 135.5 kJ mol-1
aH° (C) = 715.0 kJ mol-1
aH° (Cl2)= 242 kJ mol-1

The enthalpy change for the reaction

 CCl4 (g)  C(g) + 4Cl (g) would be -

1. 326 kJ mol-1
2. 1304 kJ mol-1
3. -328 kJ mol-1
4. -1304 kJ mol-1

Subtopic:  Thermochemistry |
 65%
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For an isolated system with ∆U = 0, the ∆S value will be-

1. Positive 2. Negative
3. Zero 4. Not possible to define
Subtopic:  Classification of System, Extensive & Intensive Properties |
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For the reaction at 298 K,

2A + B → C

ΔH = 400 kJ mol−1 and ΔS = 0.2 kJ K−1 mol−1. The reaction will become spontaneous at-

1. 1500 K
2. 2000 K
3. 100 K
4. 1900K

Subtopic:  Spontaneity & Entropy |
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For the reaction  2A(g) + B(g) → 2D(g) ; ∆U° = - 10.5 kJ and  ∆S° = - 44.1 J K-1, the value of ∆G°  for the given reaction would be-

1. 1.6 J

2. -0.16 kJ

3. 0.16 kJ

4. 1.6 kJ

Subtopic:  Gibbs Energy Change |
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The equilibrium constant for a reaction is 10. The value of G° will be:

(R = 8.314 J K-1 mol-1 ; T = 300 K)

1. -5.74 kJ mol-1
2. - 5.74 J mol-1
3. + 4.57 kJ mol-1
4. -57.4 kJ mol-1

Subtopic:  Gibbs Energy Change |
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The enthalpy of formation of COg, CO2g, N2Og , and N2O4g are

–110 kJ mol-1, – 393 kJ mol-1, 81 kJ mol-1, and 9.7 kJ mol-1 respectively.

The value of rH for the reaction would be-

N2O4g+3COgN2Og+3CO2g

1. -777.7 kJ mol-1
2.  +777.7 kJ mol-1
3.  +824.9 kJ mol-1
4. - 345.4 kJ mol-1

Subtopic:  Thermochemistry |
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The amount of heat needed to raise the temperature of 60.0 g of aluminium from 35°C to 55°C would be -

(Molar heat capacity of Al is 24 J mol-1 K-1)

1. 1.07 J
2. 1.07 kJ
3. 106.7 kJ
4. 100.7 kJ

Subtopic:  Thermodynamics' Properties and process |
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The reaction of cyanamide, NH2CN (s) with dioxygen, was carried out in a bomb calorimeter, and ∆U was found to be -742.7 kJ mol-1 at 298 K.
\(\small{\mathrm{NH}_2 \mathrm{CN}(\mathrm{s})+\frac{3}{2} \mathrm{O}_2(\mathrm{g}) \rightarrow \mathrm{N}_2(\mathrm{g})+\mathrm{CO}_2(\mathrm{g})+\mathrm{H}_2 \mathrm{O}(\mathrm{l})}\)

The enthalpy change for the reaction at 298 K would be -

1. -741.3 kJ mol-1
2. + 753.9 kJ mol-1
3. + 772. 7 kJ mol-1
4. -845. 1 kJ mol-1

Subtopic:  Enthalpy & Internal energy |
 73%
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