As an isolated box, equally partitioned, contains two ideal gasses A and B as shown:

 

When the partition is removed, the gases mix. The changes in enthalpy (∆H) and entropy (∆S) in the process, respectively, are

1. Zero, positive

2. Zero, negative

3. Positive, zero

4. Negative, zero

Subtopic:  Enthalpy & Internal energy |
 81%
Level 1: 80%+
Hints

The entropy change in the isothermal reversible expansion of 2 moles of an ideal gas from 10 to 100 L at 300 K is:
1. \(42.3 \mathrm{~J} \mathrm{~K}^{-1}\)
2. \(35.8 \mathrm{~J} \mathrm{~K}^{-1}\)
3. \(38.3 \mathrm{~J} \mathrm{~K}^{-1}\)
4. \(32.3 \mathrm{~J} \mathrm{~K}^{-1}\)

Subtopic:  Spontaneity & Entropy |
 74%
Level 2: 60%+
Hints

∆Hf0 (298K) of methanol is given by the chemical equation:

1. \(\mathrm{C}(\text { diamond })+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})}+2 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{l})}\)

2. \(\mathrm{CH}_{4(\mathrm{~g})}+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{g})}\)

3. \(\mathrm{CO}_{(\mathrm{g})}+2 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{l})}\)

4. \(\mathrm{C}(\text { graphite })+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})}+2 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{l})}\)

Subtopic:  Thermochemistry |
 78%
Level 2: 60%+
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A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 37.0ºC. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be-
(R = 8.314 J/mol K) (ln 7.5 = 2.01)

1. q = +208 J, w = -208 J 2. q = -208 J, w = -208 J
3. q = -208 J, w = + 208 J 4. q = +208 J, w = + 208 J
Subtopic:  First Law of Thermodynamics |
 83%
Level 1: 80%+
Hints

Entropy decreases during:

1. Crystallization of sucrose from solution

2. Rusting of iron

3. Melting of ice

4. Vaporization of camphor

Subtopic:  Spontaneity & Entropy |
 85%
Level 1: 80%+
Hints

Find the process showing negative entropy change:

1. Bromine (l)→Bromine(g)

2. C(s) + H2O(g) →CO(g) + H2(g)

3. N2(g,10 atm)→N2(g,1 atm) 

4. Fe ( 1mol, 400 K) → Fe( 1mol, 300 K)

Subtopic:  Spontaneity & Entropy |
 73%
Level 2: 60%+
Hints

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For the following given equations and ∆H° values, determine the enthalpy of reaction at 298 K for the reaction:

C2H4(g) + 6F2(g) → 2CF4(g) + 4HF(g)

H2(g) + F2(g) → 2HF(g)       ∆H1°= -537 kJ

C(s) + 2F2(g) →CF4(g)         ∆H2°=-680 kJ

2C(s) + 2H2(g) →C2H4(g)    ∆H3°= 52 kJ

1. –1165 kJ

2. –2486 kJ

3. +1165 kJ

4. +2486 kJ

Subtopic:  Enthalpy & Internal energy |
 83%
Level 1: 80%+
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When 4 g of iron is burnt in oxygen to form ferric oxide at constant pressure, 29.28 kJ of heat is evolved. Calculate the enthalpy of formation of ferric oxide.

(At. mass of Fe = 56) ?

1. -81.98 kJ

2. - 819.8 kJ

3. - 40.99 kJ

4.  +819.8 kJ

Subtopic:  Thermochemistry |
 59%
Level 3: 35%-60%
Hints

The standard Gibbs free energies of formation of H₂O(l), CO₂(g), and C₅H₁₂(g) at 298 K are
−237.2, −394.4 and −8.2 kJ mol⁻¹, respectively.

Calculate the standard cell potential (E°cell) of a pentane–oxygen fuel cell at 298 K.

(Given: Faraday constant, F = 96500 C mol⁻¹)

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
Hints

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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
Hints