Which of the following relations between enthalpy change $(\Delta H)$ and internal energy change $(\Delta U)$ is correct for the given reactions?

For the following reaction $Fe_2O_{3(s)} + 3 CO_{(g)} \longrightarrow 2 Fe_{(s)} + 3 CO_{2(g)}$,$\Delta H^{\circ} = -29.8 \ kJ$ and $\Delta S^{\circ} = 15 \ JK^{-1}$. What is the value of $\Delta S_{\text{total}}$ at $298 \ K$ (in $JK^{-1}$)?

For the reaction $2A_{(g)} + B_{(g)} \to 2D_{(g)}$,given $\Delta U^{\theta} = -10.5 \ kJ$ and $\Delta S^{\theta} = -44.1 \ J \ K^{-1}$. Calculate $\Delta G^{\theta}$ for the reaction at $298 \ K$ and predict whether the reaction may occur spontaneously.

An organic compound $C_xH_yO_z$ on complete combustion provides equivolume of products $CO_{2(g)}$ and $H_2O_{(g)}$,which is individually double the volume of the organic compound taken. In the process,the volume of oxygen consumed is the same as the volume of $CO_2$ produced,and the liberated heat during combustion is $500 \ kcal/mol$ at constant pressure and $500 \ K$. The formula of the organic compound and $\Delta U$ for the reaction will be:

Following data is known about the melting of a compound $AB$: $\Delta H = 9.2 \ kJ \ mol^{-1}$,$\Delta S = 0.008 \ kJ \ K^{-1} \ mol^{-1}$. Its melting point is:

What is the difference between $\Delta H$ and $\Delta U$ for the combustion of methane at $25\,^oC$?