Thermodynamics - Physical Chemistry - Chemistry Previous Year Questions

Among the following given substances, the one with zero $\Delta_f H^{\circ}$ is

The change in enthalpy $[\Delta H]$ in $\mathrm{kJ} \mathrm{mol}^{-1}$ for the reaction, $\mathrm{Mg}+2 \mathrm{~F} \longrightarrow \mathrm{MgF}_2$ is

Given, electron affinity of $\mathrm{F}=328 \mathrm{~kJ} \mathrm{~mol}^{-1}$,

IE ${ }_1$ of $\mathrm{Mg}=737 \mathrm{kJmol}^{-1}, \mathrm{IE}_2$ of $\mathrm{Mg}=1451 \mathrm{kJmol}^{-1}$

A certain mass of a gas was brought from state $A$ to $B$ by following three different paths, namely 1,2 and 3 , respectively. Which of the following relations is correct for the work done?

If 92 g Na reacts with water in open vessel at 300 K . What is the value of work done?

[Assume ideal nature of the gaseous product.]

The enthalpies of formation of gaseous $\mathrm{N}_2 \mathrm{O}$ and NO at 298 K are 82.0 and $90.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. The enthalpy change of the reaction

$\mathrm{N}_2 \mathrm{O}(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow 2 \mathrm{NO}(g)$ is

In. Observe the following properties.

1. Molar volume

II. Mass

III. Internal energy

IV. Volume

v. Enthalpy

VI. Temperature

VII. Density

The intensive properties in the above list are

Enthalpy of formation of $\mathrm{CO}(g), \mathrm{CO}_2(g)$ are -110 , $-393 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. The enthalpy of combustion of CO (in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) is

At $T(\mathrm{~K}) 2$ mole of an ideal gas is allowed to expand reversibly and isothermally from a pressure of 10 atmospheres to 1 atmosphere. The work done (in kJ ) is $\left(R=8.3 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\right)$

For the reaction at $25^{\circ} \mathrm{C}, X_2 \mathrm{O}_4(l) \longrightarrow 2 \mathrm{XO}_2(g), \Delta U$ and $\Delta S$ are 2.1 k cal and $20 \mathrm{cal} / \mathrm{K}$ respectively. What is $\Delta \mathrm{G}$ for the reaction at the same temperature? ( $R=2 \mathrm{cal} \mathrm{K}^{-1} \mathrm{~mol}^{-1}$ )

What will be the $\Delta U$ value, when one mole of oxygen $\left(\mathrm{O}_2\right)$ is going from $-20^{\circ} \mathrm{C}$ to $40^{\circ} \mathrm{C}$ at constant volume? (Molar heat capacity for oxygen $\simeq 20.8 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$ )

$\Delta H$ and $\Delta S$ for a reaction are $+30.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and 0.06 $\mathrm{kJK}^{-1} \mathrm{~mol}^{-1}$ at 1 atm pressure. The temperature at which free energy change is equal to zero and nature of the reaction below this temperature are

An air bag on adiabatic expansion undergoes $5 \%$ increase in its volume. The percentage change in pressure is $\left[\gamma_{\text {air }}=1.4\right]$

Given,

$$\mathrm{H}_2(g)+\frac{1}{2} \mathrm{O}_2(g) \longrightarrow \mathrm{H}_2 \mathrm{O}(l) ; \Delta H=-285 \mathrm{~kJ}$$

$$\begin{aligned} & \mathrm{N}_2 \mathrm{O}_5(g)+\mathrm{H}_2 \mathrm{O}(l) \longrightarrow 2 \mathrm{HNO}_3(l) ; \Delta H=-76.6 \mathrm{~kJ} \\ & \mathrm{~N}_2(g)+3 \mathrm{O}_2(g)+\mathrm{H}_2(g) \longrightarrow 2 \mathrm{HNO}_3(l) ; \\ & \Delta H=-348.2 \mathrm{~kJ} \end{aligned}$$

Calculate the $\Delta \mathrm{H}$ of $2 \mathrm{~N}_2(\mathrm{~g})+5 \mathrm{O}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{~N}_2 \mathrm{O}_5(\mathrm{~g})$.

The bond enthalpies of heavy hydrogen, $\mathrm{O}-\mathrm{O}$ and $\mathrm{D}-\mathrm{O}$ are $+400,+498$ and $+490 \mathrm{kJmol}^{-1}$, respectively. The $\Delta_r H^{\circ}$ of the reaction to produce $\mathrm{D}_2 \mathrm{O}$ is

In the reaction, $\mathrm{H}_2 \mathrm{O}(l) E \longrightarrow \mathrm{H}_2 \mathrm{O}(s)$ at $0^{\circ} \mathrm{C}$ and 1 atom, the internal energy change is $-41 \mathrm{~kJ} / \mathrm{mol}$. What will be the value of molar enthalpy change?

The correct order of " $\Delta H_f^{\circ}$ " values of diamond (I), graphite (II) and fullerene (III) is