A process among the following shows decrease in entropy is :

1. \(2 \text H \left(g\right)\rightarrow\text H_{2} \left(g\right)\)

2. Evaporation of water

3. Expansion of a gas at a constant temperature

4. Sublimation of solid to gas

Subtopic:  Gibbs Energy Change |
 82%
Level 1: 80%+
NEET - 2019
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Under the isothermal condition, a gas at \(300 \mathrm{~K}\) expands from \(0.1 \mathrm{~L}\) to \(0.25 \mathrm{~L}\) against a constant external pressure of 2 bar. The work done by the gas is:

1. \(30 ~\mathrm {J} \) 2. \(-30 ~\mathrm{J} \)
3. \(5~ \mathrm{kJ}\) 4. \(25~ \mathrm{J}\)
Subtopic:  2nd & 3rd Law of Thermodynamics |
 81%
Level 1: 80%+
NEET - 2019
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Assuming each reaction is carried out in an open container,
Reaction that shows ΔH=ΔE is :

1. H2(g)+Br2(g)2HBr(g)

2. C(s)+2H2O(g)2H2(g)+CO2(g)

3. PCl5(g)PCl3(g)+Cl2(g)

4. 2COg+O2g2CO2g

Subtopic:  Thermodynamics' Properties and process |
 81%
Level 1: 80%+
AIPMT - 2006
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The bond energy of H—H and Cl-Cl is 430 kJ
mol-1 and 240 kJ mol-1 respectively and ΔHf for HCl is -90 kJ mol-1. The bond enthalpy of HCl is:

1. 290 kJ mol-1

2. 380 kJ mol-1

3. 425 kJ mol-1

4. 245 kJ mol-1

Subtopic:  Thermochemistry |
 63%
Level 2: 60%+
AIPMT - 2007
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Bond dissociation enthalpy of H2, Cl2, and HCl are 434, 242, and 431 kJ mol1 respectively. Enthalpy of formation of HCl is:

1. 93 kJ mol-1
2. - 245 kJ mol-1
3. -93 kJ mol-1
4. 245 kJ mol-1

Subtopic:  Thermochemistry |
 66%
Level 2: 60%+
AIPMT - 2008
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The standard free energies of formation(in kJ/mol) at 298 K are -237.2, -394.4, and -8.2 for H2O(l), CO2(g), and pentane (g), respectively. The value of Ecell for the pentane-oxygen fuel cell is:

1. 1.968 V
2. 2.0968 V
3. 1.0968 V
4. 0.0968 V

Subtopic:  Gibbs Energy Change |
 52%
Level 3: 35%-60%
AIPMT - 2008
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For the gas phase reaction, 
 PCl5(g)PCl3(g)+Cl2(g)
which of the following conditions is correct?

1. ΔH = 0 and ΔS < 0

2. ΔH > 0 and ΔS > 0

3. ΔH < 0 and ΔS < 0

4. ΔH > 0 and ΔS < 0

Subtopic:  Gibbs Energy Change |
 83%
Level 1: 80%+
AIPMT - 2008
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The values of ΔH and ΔS for the given reaction are 170 kJ and 170 JK-1, respectively.
C(graphite) + CO2(g)→2CO(g) 
This reaction will be spontaneous at:

1. 710 K
2. 910 K
3. 1110 K
4. 510 K

Subtopic:  Gibbs Energy Change |
 88%
Level 1: 80%+
AIPMT - 2009
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Give 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 following reaction 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:  Thermochemistry |
 76%
Level 2: 60%+
AIPMT - 2009
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Standard entropies of X2, Y2 and XY3 are 60, 40 and 50JK-1mol-1 respectively. For the reaction 
12X2 + 32Y2   XY3 ; H = -30 kJ to be at equilibrium, the temperature should be:

1. 750 K

2. 1000 K

3. 1250 K

4. 500 K

Subtopic:  Gibbs Energy Change |
 79%
Level 2: 60%+
AIPMT - 2010
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