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.

Calculate the enthalpy change of the reaction,
$\text{H}_2\text{(g)} + \text{Cl}_2\text{(g)} \rightarrow 2\text{HCl(g)}$
if bond energies (kJ mol$^{-1}$):
H–H = 436, Cl–Cl = 242, H–Cl = 431