In a reaction, $\mathrm{\Delta H}$ and $\mathrm{\Delta S}$, both are more than zero. In which of the following cases would the reaction be spontaneous?

The difference between the heat of reaction at constant pressure and constant volume for the reaction: $2{\mathrm{C}}_6{\mathrm{H}}_6 \left(\mathrm{l}\right)+15{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 12{\mathrm{CO}}_2 \left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right)$ at $25°\mathrm{C}$ in $\mathrm{kJ}$ is:

When steam condenses to water at $90°\mathrm{C}$, the entropy of the system decreases. What must be true if the second law of thermodynamics is to be satisfied?

[Hint: For a spontaneous process ${\mathrm{\Delta S}}_{\text{universe}}$ must be positive.]

For the reaction, $\frac{1}{2}{\mathrm{A}}_2+\frac{1}{2}{\mathrm{B}}_2\to \mathrm{AB}; \mathrm{\Delta H}=-50 \mathrm{kcal}$.

If the bond energies of ${\mathrm{A}}_2, {\mathrm{B}}_2$ and $\mathrm{AB}$ are $\mathrm{x}, \frac{\mathrm{x}}{2}$ and $\mathrm{x} \mathrm{kcal}$, respectively, the value of $\mathrm{x}$ is: