The enthalpy of combustion of cyclohexane, cyclohexene and $\text{H}_2$ are respectively $-3920, -3800$ and $-241$ KJ mol$^{-1}$. The enthalpy of hydrogenation of cyclohexene is

A gas expands from a volume of $1$ dm$^3$ to $1.25$ dm$^3$ under a pressure of $1$ bar. Find the change in internal energy if $150$ J of heat is supplied to the system.

In which of the following processes the internal energy of system remain constant?

For a certain reaction $\Delta H = -50$ kJ and $\Delta S = -100$ J/K find the temperature so that the reaction is spontaneous.