For a reaction,$X_{2(g)} + Y_{2(g)} \rightleftharpoons 2XY_{(g)}$. If $\Delta G_r^o = 20 \ kJ \ mol^{-1}$ and $\Delta S_r^o = -20 \ J \ K^{-1} \ mol^{-1}$ at $200 \ K$. Calculate $\Delta H_r^o$ at $400 \ K$ (Given $\Delta_r C_P = 20 \ J \ K^{-1} \ mol^{-1}$).

The standard enthalpies of formation of $1,3-butadiene(g)$,$CO_{2(g)}$,and $H_2O_{(l)}$ at $298 \ K$ are $-30$,$-94$,and $-68 \ kcal/mol$ respectively. If the magnitude of resonance enthalpies of $1,3-butadiene$ and $CO_2$ are $10$ and $20 \ kcal/mol$ respectively,the enthalpy of combustion of $1,3-butadiene(g)$ at $298 \ K$ is $........ \ kcal/mol$. (Enthalpy of vaporization of $H_2O_{(l)}$ at $298 \ K = 10 \ kcal/mol$)

Which of the following is not a correct statement?

Latent heat of vaporisation of a liquid at $500 \ K$ and $1 \ atm$ pressure is $20.0 \ kcal/mol$. What will be the change in internal energy $(\Delta E)$ of $3 \ mol$ of liquid at same temperature in $kcal$?

For the reactions,$C + O_2 \to CO_2; \Delta H = -393 \ J$
$2Zn + O_2 \to 2ZnO; \Delta H = -412 \ J$

For the reaction $2C_6H_6(l) + 15O_2(g) \rightarrow 12CO_2(g) + 6H_2O(l)$ at $25 \ ^\circ C$,calculate the difference between the heat of reaction at constant volume and constant pressure in $kJ$.