[UPSC CSE 2015] Thermodynamics (Q81, 15M)

The vapour pressure of an organic substance is 50\times10^3\ \mathrm{Pa} at 40^{\circ}\mathrm{C}. Its normal boiling point is 80^{\circ}\mathrm{C}. If the substance in vapour phase can be treated like an ideal gas, find the latent heat of vaporization of the substance.