Thermodynamics practice · Medium

White phosphorus is a tetra atomic solid $\mathrm{P}_4(\mathrm{s})$ at room temperature. Find average $(\mathrm{P}-\mathrm{P})$ bond enthalpy (in $\mathrm{kJ} / \mathrm{mol}$).
Given: $\Delta \mathrm{H}_{\text {sublimation}}$ of $\mathrm{P}_4(\mathrm{s})=59 \mathrm{~kJ} / \mathrm{mol}$
$\Delta \mathrm{H}_{\text {atomization}}$ of $\mathrm{P}_4(\mathrm{s})=1265 \mathrm{~kJ} / \mathrm{mol}$

The calorific value of fat is :

Assertion (A): The solubility of most salts in water increases with rise in temperature.
Reason (R): For most of the ionic compounds, $\Delta_{\text {sol }} H^{\circ}$ is positive and the dissociation process is endothermic.

Which law states entropy of all pure crystalline
solids is zero at absolute zero?

For non ideal solution showing positive deviation from Rault's law :

Statement I : Enthalpy changes are positive when $N{a_2}S{O_4}.10\,{H_2}O,\,CuS{O_4}.5{H_2}O$ and salts like $NaCl$, $KCl$ etc., which do not form hydrates are dissolved in water. But enthalpy changes are negative when anhydrous salts capable of forming hydrates are dissolved in water
Statement II : The difference in the behaviour is due to large differences in the molecular weight of hydrated and anhydrous salts. The substances with larger molecular weights usually show positive enthalpy changes on dissolution.

The value of $\Delta \mathrm{H}$ for cooling 2 mole of an ideal monoatomic gas from $225^{\circ} \mathrm{C}$ to $125^{\circ} \mathrm{C}$ to at constant pressure will be $\left[\right.$ given $\left.C_p=\frac{5}{2} R\right]$

Calculate the difference between heat of combustion of carbon monoxide gas at constant pressure and at constant volume at $27^{\circ} \mathrm{C}$ ? $(\mathrm{R}=$ 2 cal K $\mathrm{mol}^{-1}$ )

For spontaneous process:

Statement (S): Heat given out during neutralisation of $\mathrm{NaOH}$ and $\mathrm{HF}$ is $-13.7 \mathrm{~k~cal} / \mathrm{eq}$.

Explanation (E): $\mathrm{F}^{-}$ion is more easily hydrated and thus heat of neutralisation of $\mathrm{HF}$ and $\mathrm{NaOH}$ is more.

Calculate $\Delta H$ for the following reaction at $298 \mathrm{~K},$

$\mathrm{Fe}_2 \mathrm{O}_3(\mathrm{s})+3 \mathrm{CO}(\mathrm{g}) \rightarrow 2 \mathrm{Fe}(\mathrm{s})+3 \mathrm{CO}_2(\mathrm{g})$

from the following thermochemical equations.

(i) $3 \mathrm{Fe}_2 \mathrm{O}_3(\mathrm{s})+\mathrm{CO}(\mathrm{g}) \rightarrow 2 \mathrm{Fe}_3 \mathrm{O}_4(\mathrm{s})+\mathrm{CO}_2(\mathrm{g});\Delta H=-46.4 \mathrm{~kJ}$

(ii) $\mathrm{FeO} \text{(s)} +\mathrm{CO}(\mathrm{g}) \rightarrow \mathrm{Fe} \text{(s)} +\mathrm{CO}_2 \text{(g)}; \Delta H=9.0 \mathrm{~kJ}$

(iii) $\mathrm{Fe}_3 \mathrm{O}_4 \text{(s)} +\mathrm{CO}(\mathrm{g}) \rightarrow 3 \mathrm{FeO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{g}); \Delta H=-41.0 \mathrm{~kJ}$

The correct thermodynamic conditions for the process which is spontaneous only at low temperature is

Internal energy of an ideal gas depends on:

Which one among the following is the correct expression for isothermal reversible change?

Regarding the internal energy of the molecule, which of the following statement is correct

If enthalpy of combustion of $C$ (graphite) is $x({~kJ} / {mol})$ then enthalpy of formation (in ${kJ} / {mol}$ ) of ${CO}_2({~g})$ will be

(Given : Enthalpy of sublimation of $C(s)$ is ${y}\, {kJ} / {mol}$ )

When equal volumes of Helium and Neon at same temperature and pressure are mixed, the ratio $C_p: C_v$ of the mixture equals

The normal boiling point and $\Delta {H}_{\text {vap }}$ of a liquid ' ${X}$ ' are $400 {~K}$ and $40 {~kJ} {~mol}^{-1}$ respectively. Assuming $\Delta {H}_{\text {vap }}$ to be constant, which of the following is correct?
(I) $\Delta {S}_{\text {vap }}>100 {JK}^{-1} {~mol}^{-1}$ at $400 {~K}$ and $0.5 {~atm}$
(II) $\Delta {S}_{\text {vap }} < 100 {JK}^{-1} {~mol}^{-1}$ at $400 {~K}$ and $1 {~atm}$
(III) $\Delta {S}_{\text {vap }} < 100 {JK}^{-1} {~mol}^{-1}$ at $400 {~K}$ and $2 {~atm}$
(IV) $\Delta {S}_{\text {vap }}=100 {JK}^{-1} {~mol}^{-1}$ at $400 {~K}$ and $1 {~atm}$

Four monobasic acids A,B,C and D have their respective ${\Delta _{neut}}{H^0}$ values are -11.5 , -7.5, -12.4 and -8.9 kcal/mol. Which of the following acids has the highest pKa value ?

The heat of combustion of a substance is :

For the reaction, at $1000^{\circ} \mathrm{C}$, $\mathrm{CaCO}_3(\mathrm{~s}) \longrightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_2(g)$
$\Delta G^{\circ}=-27 \mathrm{~kJ} \mathrm{~mol}^{-1}, p_{\mathrm{CO}_2}=0.0033 \mathrm{~atm}$.
Hence, $\Delta G$ at this temperature is

How many gram of butane must be burnt to heat $10 \mathrm{~kg}$ water from $30^{\circ} \mathrm{C}$ to $100^{\circ} \mathrm{C}$. Heat of combustion of butane is $-700 \mathrm{kcal} / \mathrm{mol}$ and specific heat of water is $1 \mathrm{cal} \mathrm{gm}^{-1} \mathrm{~K}^{-1}$.

Statement - I: When any hydrocarbon is burnt, the moles of oxygen needed for complete
combustion is always greater than the moles of hydrocarbon burnt.

Statement - II: Complete combustion of any substance requires more moles of oxygen than
the moles of substance burnt.

If latent heat of vaporization is $L$ at boiling point $T\left( \mathrm{K} \right)$ then entropy of vaporisation is

In a container, two mole of a diatomic ideal gas is allowed to expand against 1 atm pressure & volume change from 2 litre to 5 litre isobarically then calculate change in internal energy.

The process in which pressure remains constant throughout a change is:

2 moles of oxygen gas is heated at constant volume from $10^{\circ} {C}$ to $30^{\circ} {C}$. If molar heat capacity at constant volume is $5.03 {cal} / {mol}-{K}$. Then change in internal energy will be :-

Exactly $100 \mathrm{~J}$ of heat was transferred reversibly to a block of gold at $25.00^{\circ} \mathrm{C}$ from a thermal reservoir at $25.01^{\circ} \mathrm{C}$, and then exactly $100 \mathrm{~J}$ of heat was absorbed reversibled from the block of gold by a thermal reservoir at $24.99^{\circ} \mathrm{C}$. Thus, entropy change of the system is

One mole of an ideal gas at 300K is expanded isothermally from an initial volume of 1 litre to 10 litre. The ∆U for this process is $\left( {R = 2\mathrm{cal}{\mathrm{K}^{ - 1}}\mathrm{mo}{\mathrm{l}^{ - 1}}} \right)$

Equal volumes of monoatomic and diatomic gases at same initial temperature and pressure are mixed. The ratio of specific heats of the mixture $\;({C_p}/{C_v})$will be