The standard enthalpy of vaporisation vapH° for water at 100°C is 40.66 kJ mol-1. The

internal energy of vaporisation of water at 100°C (in kJ mol-1) is- 

(Assume water vapour to behave like an ideal gas)

1. +37.56                   

2. -43.76

3. +43.76                   

4. +40.66

Subtopic:  Enthalpy & Internal energy |
 57%
From NCERT
NEET - 2012
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If the enthalpy change for the transition of liquid water to steam is 30 kJ mol-1 at 27°C,

the entropy change for the process would be

1. 1.0 J mol-1 K-1

2. 0.1 J mol-1K-1

3. 100 J mol-1K-1

4. 10 J mol-1K-1

Subtopic:  Enthalpy & Internal energy |
 81%
From NCERT
NEET - 2011
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Which of the following options correctly describes the free expansion of an ideal gas under adiabatic conditions?
1. \(\mathrm{q} \neq 0, \quad \Delta \mathrm{T}=0, \quad \mathrm{~W}=0\)
2. \(\mathrm{q}=0, \quad \Delta \mathrm{T}=0, \quad \mathrm{~W}=0\)
3. \(\mathrm{q}=0, \quad \Delta \mathrm{T}<0, \quad \mathrm{~W} \neq 0\)
4. \(\mathrm{q}=0, \quad \Delta \mathrm{T} \neq 0, \quad \mathrm{~W}=0\)

Subtopic:  Thermodynamics' Properties and process |
 68%
From NCERT
NEET - 2011
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Enthalpy change for the reaction,

 4H(g) 2H2(g) is -869.6 kJ

The dissociation energy of H-H bond is

1. -869.6 kJ                 

2. + 434.8 kJ

3. +217.4 kJ                 

4. -434.8 kJ

Subtopic:  Thermochemistry |
 63%
From NCERT
NEET - 2011
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From the following bond energies:

H-H bond energy: 431.37 kJ mol-1

C=C bond energy : 606.10 kJ mol-1

C-C bond energy : 336.49 kJ mol-1

C-H bond energy : 410.50 kJ mol-1

Enthalpy for the reaction,

C|H|H=C|H|H+H-HH-C|H|H-C|H|H-H

will be

1. 1523.6 kJ mol-1

2. -243.6 kJ mol-1

3. -120.0 kJ mol-1

4. 553.0 kJ mol-1

Subtopic:  Hess's Law |
 69%
From NCERT
NEET - 2009
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The values of H and S for the given reaction are 170 kJ and 170 JK–1, respectively.
\(\mathrm{C} \text { (graphite) }+\mathrm{CO}_2(\mathrm{~g}) \rightarrow 2 \mathrm{CO}(\mathrm{g})\)
This reaction will be spontaneous at:

1. 710 K

2. 910 K

3. 1110 K

4. 510 K

Subtopic:  Gibbs Energy Change |
 84%
From NCERT
NEET - 2009
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Which of the following are not state functions?

(I) q + W                        (II) q

(III) W                           (IV) H-TS

1. (I) and (IV)                     

2. (II), (III) and (IV)

3. (I) , (II) and (III)               

4.  (II) and (III)

Subtopic:  Classification of System, Extensive & Intensive Properties |
 71%
From NCERT
NEET - 2008
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Consider the following reactions :

(i) H+(aq) + OH-(aq) = H2O(l) H = -x1 kJ mol-1

(ii) H2(g) + 12O2(g) = H2O(l) H = -x2 kJ mol-1

(iii) CO2(g) + H2(g) = CO(g) + H2O(l) H = -x3 kJ mol-1

(iv) C2H5(g) + 52O2(g) = 2CO2(g) + H2O(l) H = -x4 kJ mol-1

Enthalpy of formation of H2O(l) is:

1. -x2 kJ mol-1 

2. +x3 kJ mol-1

3. -x4 kJ mol-1

4. -x1 kJ mol-1

Subtopic:  Enthalpy & Internal energy |
 75%
From NCERT
NEET - 2007
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Identify the correct statement for change of Gibbs energy for a system (Gsystem) at constant temperature and pressure:

(1) If Gsystem > 0, the process is spontaneous

(2) If Gsystem = 0, the system has attained equilibrium

(3) If Gsystem = 0, the system is still moving in a particular direction

(4) If Gsystem < 0, the process is not spontaneous

Subtopic:  Gibbs Energy Change |
 87%
NEET - 2006
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The enthalpy and entropy change for the reaction :

Br2 (l) + Cl2 (g) 2BrCl (g)

are 30 kJ mol-1 and 105 J K-1 mol-1 respectively.

The temperature at which the reaction will be in equilibrium is :

1. 285.7 K 2. 273.4 K
3. 450.9 K 4. 300.1 K
Subtopic:  Spontaneity & Entropy |
 82%
From NCERT
NEET - 2006
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