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 reaction, 

C(graphite) + CO2(g) 2CO(g) are 170 kJ and 170 JK-1, respectively. 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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Links
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The enthalpy of combustion of H2, cyclohexene (C6H10) and cyclohexane (C6H12) are -241, -3800 and -3920 kJ per mol respectively. Heat of hydrogenation of cyclohexene is:

(a) -121 kJ per mol

(b) +121 kJ per mol

(c) +242 kJ per mol

(d) -242 kJ per mol

Subtopic:  Thermochemistry |
 59%
NEET - 2006
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Consider the reactionat 300K

H2(9) + Cl2(9) →2HCI(g), ΔH° = — 185 KJ

If 3 mole of H2 completely react with 3 mol of Cl2 to form Cl, U° of the reaction will be

(1) Zero

(2) –185 KJ

(3) -555 KJ

(4) None

Subtopic:  2nd & 3rd Law of Thermodynamics |
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For a perfectly crystalline solid Cpm = aT3, where a is constant. If Cpm is 0.42 J/K–mol at 10 K, molar entropy at 10 K is

1. 0.42 J/K–mol

2. 0.14 J/K–mol

3. 4.2 J/K–mol

4. zero

Subtopic:  Spontaneity & Entropy |
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