If for a certain reaction rH is 30 kJ mol–1 at 450 K, the value of rS (in JK–1 mol–1) for which the same reaction will be spontaneous at the same temperature is:

1. 70

2. –33

3. 33

4. –70

Subtopic:  Spontaneity & Entropy |
 69%
From NCERT
NEET - 2020
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At standard conditions, if the change in the enthalpy for the following reaction is –109 kJ mol
H2(g)+Br2(g)2HBr(g) and the bond energy of H2 and Br2 is 435 kJ mol–1 and 192 kJ mol–1 respectively, what is the bond energy (in kJ mol–1) of HBr?

1. 368 2. 736
3. 518 4. 259
Subtopic:  Thermochemistry |
 53%
From NCERT
NEET - 2020
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Consider the following processes:

                                       ∆H (kJ/mol)
½ A → B                            + 150
3B → 2C + D                      –125
E + A → 2D                        +350

For B + D → E + 2C, ∆H will be-

1. 325 kJ/mol 

2. 525 kJ/mol

3. –175 kJ.mol 

4. –325 kJ/mol

Subtopic:  Enthalpy & Internal energy |
 72%
From NCERT
AIPMT - 2011
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For vaporization of water at 1 atmospheric pressure, the values of ∆H and ∆S are 40.63 kJ mol–1 and 108.8 JK–1 mol–1, respectively. The temperature when Gibbs energy change (∆G) for this transformation will be zero, is:

1. 393.4 K

2. 373.4 K

3. 293.4 K

4. 273.4 K

Subtopic:  Gibbs Energy Change |
 78%
From NCERT
AIPMT - 2010
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Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be:

1. 3 Joules

2. 9 Joules

3. Zero

4. Infinite

Subtopic:  First Law of Thermodynamics |
 90%
From NCERT
AIPMT - 2010
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The following two reactions are knownFe2O3(s)+3CO(g)2Fe(s)+3CO2(g);
H=-26.88 kJ
FeO(s)+CO(g)Fe(s)+CO2(g);
H=-16.5 kJ

The value of H for the following reaction

Fe2O3(s)+CO(g)2FeO(s)+CO2(g) is:

1. -43.3 kJ

2. -10.3 kJ

3. +6.2 kJ

4. +10.3 kJ

Subtopic:  Enthalpy & Internal energy |
 76%
From NCERT
AIPMT - 2010
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Match List – I (Equations) with List – II (Type of processes) and select the correct option.

List – I List – II
Equation  Type of processes
(a) Kp > Q  (i) Non-spontaneous
(b) ∆Gº < RT ln Q  (ii) Equilibrium
(c) Kp = Q  (iii) Spontaneous and endothermic
(d) T > \(\frac{\Delta H}{\Delta S}\) (iv) Spontaneous
 
Options: (a) (b) (c) (d)
1. (iii) (iv) (ii) (i)
2. (iv) (i) (ii) (iii)
3. (ii) (i) (iv) (iii)
4. (i) (ii) (iii) (iv)
Subtopic:  Spontaneity & Entropy | Gibbs Energy Change |
 63%
From NCERT
AIPMT - 2010
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A reaction occurs spontaneously if:

1. T∆S > ∆H and ∆H is +ve and ∆S are –ve

2. T∆S = ∆H and both ∆H and ∆S are +ve

3. T∆S < ∆H and both ∆H and ∆S are +ve

4. T∆S > ∆H and both ∆H and ∆S are +ve

Subtopic:  Spontaneity & Entropy |
 76%
From NCERT
AIPMT - 2005
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Which of the following pairs of chemical reactions is certain to result in a spontaneous reaction:

1. Endothermic and decreasing disorder

2. Exothermic and increasing disorder

3. Endothermic and increasing disorder

4. Exothermic and decreasing disorder

Subtopic:  Spontaneity & Entropy |
 76%
From NCERT
AIPMT - 2005
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Identify the correct statement regarding entropy:

1. At absolute zero of temperature, the entropy of all crystalline substances is taken to be zero
2. At absolute zero of temperature, the entropy of a perfectly crystalline substance is +ve
3. At absolute zero of temperature, the entropy of a perfectly crystalline substance is taken to be zero
4. At 0 °C , the entropy of a perfectly crystalline substance is taken to be zero
Subtopic:  2nd & 3rd Law of Thermodynamics |
 64%
From NCERT
AIPMT - 1998
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