Thermodynamics

When a solid melts reversibly :

• H decreases

• G increases

• E decreases

• S increases

Enthalpy is equal to :

• ${\mathrm{T}}^2{\left[\frac{\partial (\mathrm{G}/\mathrm{T})}{\partial \mathrm{T}}\right]}_P$

• $-{\mathrm{T}}^2{\left[\frac{\partial (\mathrm{G}/\mathrm{T})}{\partial \mathrm{T}}\right]}_{\mathrm{P}}$

• ${\mathrm{T}}^2{\left[\frac{\partial (\mathrm{G}/\mathrm{T})}{\partial \mathrm{T}}\right]}_V$

• $-{\mathrm{T}}^2{\left[\frac{\partial (\mathrm{G}/\mathrm{T})}{\partial \mathrm{T}}\right]}_{\mathrm{V}}$

Condition for spontaneity in an isothermal process is

• $∆\mathrm{A} + \mathrm{W} < 0$

• $∆\mathrm{G} + \mathrm{U} <0$

• $∆\mathrm{A} + \mathrm{U}>0$

• $∆\mathrm{G} -\mathrm{U}<0$

$$\begin{gathered} 2\mathrm{C}\left(\mathrm{s}\right) + 2{\mathrm{O}}_2\left(\mathrm{g}\right) \to 2{\mathrm{CO}}_2\left(\mathrm{g}\right); ∆\mathrm{H}= -787 \mathrm{kJ} ....\left(\mathrm{i}\right) \\ {\mathrm{H}}_2\left(\mathrm{g}\right) + \frac{1}{2}{\mathrm{O}}_2\left(\mathrm{g}\right) \to {\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right); ∆\mathrm{H} = -286 \mathrm{kJ} ...\left(\mathrm{ii}\right) \\ {\mathrm{C}}_2{\mathrm{H}}_2\left(\mathrm{g}\right) + 2\frac{1}{2}{\mathrm{O}}_2\left(\mathrm{g}\right) \to 2{\mathrm{CO}}_2\left(\mathrm{g}\right) + {\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right) ; ∆\mathrm{H}= -1310 \mathrm{kJ} ...\left(\mathrm{iii}\right) \end{gathered}$$

The heat of formation of acetylene is :

• -1802 kJ

• +1802 kJ

• +237 kJ

• -800 kJ

The standard molar heat of formation of ethane, CO₂ and water (l) are -21.1, -94.1 and -68.3 kcal respectively. The standard molar heat of combustion of ethane will be

• -372 kcal

• 162 kcal

• -240 kcal

• 183.5 kcal

For the reaction,

$2{\mathrm{H}}_2\left(\mathrm{g}\right) + {\mathrm{O}}_2\left(\mathrm{g}\right) \to 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right), ∆\mathrm{H}°= - 573.2 \mathrm{kJ}$

The heat of decomposition of water per mole is

• 286.6 kJ

• 573.2 kJ

• -28.66 kJ

• Zero

Hess's law is based on

• law of conservation of mass

• law of conservation of energy

• first law of thermodynamics

• None of the above

Which of the following is a path function?

• Internal energy

• Enthalpy

• Work

• Entropy

If for the cell reaction,

Zn + Cu²⁺ $\rightleftharpoons$ Cu + Zn²⁺;

entropy change $∆\mathrm{S}°$ is 96.5 J mol^-1K^-1, then temperature coefficient of the emf of a cell is

• 5 × 10^-4 VK^-1

• 1 × 10^-3 VK^-1

• 2 × 10^-3 VK^-1

• 9.65 × 10^-4 VK^-1

Cell reaction is spontaneous, when

• ${\mathrm{E}}_{\mathrm{red}}^{°} \mathrm{is} \mathrm{negative}$

• ${\mathrm{E}}_{\mathrm{red}}^{°} \mathrm{is} \mathrm{positive}$

• $∆\mathrm{G}° \mathrm{is} \mathrm{negative}$

• $∆\mathrm{G}° \mathrm{is} \mathrm{positive}$