# At constant pressure and temperature, the direction of any chemical reaction is one where the...... decrease. 1. Entropy                2. Enthalpy 3. Gibbs energy        4. None of the above

Subtopic:  Spontaneity & Entropy |
55%
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The work done by a mass less piston in causing an expansion $∆$V (at constant temperature), when the opposing pressure, P is variable, is given by:

1. W= $-\int \mathrm{P}∆\mathrm{V}$

2. W=0

3. W= -P$∆$V

4. none of these

Subtopic:  2nd & 3rd Law of Thermodynamics |
65%
From NCERT
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Entropy decreases during:

1. crystallization of sucrose from solution

2. rusting of iron

3. melting of ice

4. vaporization of camphor

Subtopic:  Spontaneity & Entropy |
72%
From NCERT
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Entropy change of vaporization at constant pressure is given by:

1.

2. $∆{\mathrm{S}}_{\mathit{\left(}v\mathit{\right)}}=\frac{∆{\mathrm{U}}_{v}}{\mathrm{T}}$

3.

4. None of the above

Subtopic:  Spontaneity & Entropy |
75%
From NCERT
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What is the entropy change for the reaction given below,

2H2 (g) + O2 (g) $\to$2H2O(l)

at temperature 300 K? Standard entropies of H2 (g), O2(g) and H2O(l) are 126.6, 201.20 and 68.0 JK-1mol-1 respectively.

1. -318.4 JK-1mol-1                           .

2. 318.4 JK-1mol-1

3. 31.84 JK-1mol-1

4. none of these

Subtopic:  Spontaneity & Entropy |
72%
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If S$°$ for H2, Cl2 and HCl are 0.13, 0.22 and 0.19 kJ K-1mol-1 respectively. The total change in standard entropy for the reaction, H2 + Cl2 $\to$2HCl is:

1. 30 J K-1mol-1

2. 40 J K-1mol-1

3. 60 J K-1mol-1

4. 20 J K-1mol-1

Subtopic:  Spontaneity & Entropy |
80%
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The direct conversion of A to B is difficult and thus it is converted by path A$\to$C$\to$D$\to$B. Given

(Where e.u. is the entropy unit)
then $∆{\mathrm{S}}_{\mathrm{A}\to \mathrm{B}}$ would be:

1. +60 e.u

2. +100 e.u

3. -60 e.u

4. -100 e.u

Subtopic:  Hess's Law |
60%
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In a flask, colourless N2O4(g) is in equilibrium with brown coloured NO2(g). At equilibrium when the flask is heated to 100$°$C, the brown colour deepens and on cooling it becomes less coloured. Which statement is incorrect about this observation?

1. The $∆$H for the reaction N2O4(g)$⇌$ 2NO2(g) is +ve

2. Paramagnetism increases on heating

3. The $∆$H-$∆$U at 100$°$C is equal to 200 cal

4. Dimerisation is reduced on heating

Subtopic:  First Law of Thermodynamics |
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Enthalpy of the reaction,

CH4(g) + 1/2O2(g) CH3OH(l), is negative. If the enthalpy of combustion of CH4 and CH3OH are x and y respectively, then
which relation is correct?

1. x>y

2. x<y

3. x=y

4. x$⩾$y

Subtopic:  Enthalpy & Internal energy |
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In the reaction, $∆$H and $∆$S both are positive. The condition under which the reaction would not be spontaneous is -

1. $∆$H>T$∆$S

2. $∆$S=$∆$H/T

3. $∆$H=T$∆$S

4. All of the above

Subtopic:  Gibbs Energy Change |
54%
From NCERT
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