Chapter 4

The entropy change for a phase transformation is : (a) \(\frac{\Delta U}{\gamma+d T}\) (b) \(\frac{\Delta T}{\Delta H}\) (c) \(\frac{\Delta H}{T}\) (d) \(\frac{\Delta H+\Delta G}{T}\)

What is the melting point of benzene if \(\Delta H_{\text {fusion }}=9.95 \mathrm{~kJ} / \mathrm{mol}\) and \(\Delta S_{\text {fusion }}=35.7 \mathrm{~J} / \mathrm{K}\) -mol? (a) \(278.7^{\circ} \mathrm{C}\) (b) \(278.7 \mathrm{~K}\) (c) \(300 \mathrm{~K}\) (d) \(298 \mathrm{~K}\)

Chloroform has \(\Delta H_{\text {vaporization }}=29.2 \mathrm{~kJ} / \mathrm{mol}\) and boils at \(61.2^{\circ} \mathrm{C} .\) What is the value of \(\Delta S_{\text {vaporization }}\) for chloroform? (a) \(87.3 \mathrm{~J} / \mathrm{mol}-\mathrm{K}\) (b) \(477.1 \mathrm{~J} / \mathrm{mol}-\mathrm{K}\) (c) \(-87.3 \mathrm{~J} / \mathrm{mol}-\mathrm{K}\) (d) \(-477.1 \mathrm{~J} / \mathrm{mol}-\mathrm{K}\)

Identify the correct statement regarding entropy (a) At absolute zero temperature, the entropy of perfectly crystalline substances is \(+\mathrm{ve}\) (b) At absolute zero temperature entropy of perfectly crystalline substance is taken to be zero (c) At \(0^{\circ} \mathrm{C}\) the entropy of a perfectly crystalline substance is taken to be zero (d) At absolute zero temperature, the entropy of all crystalline substances is taken to be zero

Calculate \(\Delta S\) for following process: $$ \underset{\text { at } 100 \mathrm{~K}}{X(s)} \longrightarrow \underset{\text { at } 200 \mathrm{~K}}{X(l)} $$ Given : Melting point of \(X_{(s)}=100 \mathrm{~K} ; \Delta H_{\text {Fusion }}=20 \mathrm{~kJ} / \mathrm{mol} ; C_{p, m}(X, l)=10 \mathrm{~J} / \mathrm{mol} \mathrm{K}\) (a) \(26.93 \mathrm{~J} / \mathrm{K}\) (b) \(206.93 \mathrm{~J} / \mathrm{K}\) (c) \(203 \mathrm{~J} / \mathrm{K}\) (d) \(206.93 \mathrm{~kJ} / \mathrm{K}\)

For the reaction \(2 \mathrm{H}(g) \longrightarrow \mathrm{H}_{2}(g)\), the sign of \(\Delta H\) and \(\Delta S\) respectively are : (a) \(+,-\) (b) \(+,+\) (c) \(-,+\) (d) \(-,-\)

Consider the following reaction. $$ \mathrm{C}_{6} \mathrm{H}_{6}(l)+\frac{15}{2} \mathrm{O}_{2}(g) \longrightarrow 6 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g) $$ signs of \(\Delta H, \Delta S\) and \(\Delta G\) for the above reaction will be (a) \(+,-,+\) (b) -, +, - (c) \(-,+,+\) (d) \(+,+,-\)

Consider the following reaction at temperature \(T\) : $$ \begin{aligned} &\mathrm{CH}_{2}=\mathrm{CH}_{2}(g)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}(g) \\ &\Delta_{r} H^{\circ}=-217.5 \mathrm{~kJ} / \mathrm{mol}, \quad \Delta_{r} S^{\circ}=-233.9 \mathrm{~J} / \mathrm{K}-\mathrm{mol} \end{aligned} $$ Reaction is supported by : (a) entropy (b) enthalpy (c) both (a) \& (b) (d) neither

For a process to be spontaneous at constant \(T\) and \(P\) : (a) \((\Delta G)_{\text {system }}\) must be negative (b) \((\Delta G)_{\text {system }}\) must be positive (c) \((\Delta S)_{\text {system }}\) must be positive (d) \((\Delta S)_{\text {system }}\) must be negative

Which of the following conditions regarding a chemical process ensures its spontaneity at all temperature? (a) \(\Delta H>0, \Delta G<0\) (b) \(\Delta H<0, \Delta S>0\) (c) \(\Delta H<0, \Delta S<0\) (d) \(\Delta H>0, \Delta S<0\)