Write the thermochemical equation corresponding to the standard enthalpy of formation of benzne. (Hint: `Delta_fH^Theta` of benzene = `+49.0 kJ mol^-1`)

a) What is meant by enthalpy of formation? b) What is the value of standard enthalpy of formation ( Delta_fH^o ) of an element?

Internal energy, enthalpy and entropy are thermodynamics state functions. Calculate enthalpy of combustion of methane, given that the standard enthalpies of formation of CH_4 , CO_2 and H_2O are -75.2, -394.0 and -285.6 kJ//mol respectively.

a) Predict whether entropy increases or decreases in the following changes: i) l_2(S)rightarrowl_2(g) ii) Temperature of a crystalline solid is raised from 0 K and 115 K. iii) Freezing of water b) Calculate the enthalpy of combustion of methane. Given that standard enthalpies of formation of CH_4,CO_2 and H_2O are -75.2, -394 and -285.6 kJ/mol respectively.

A glass vassel after washing contain 54 g of water in it. How much heat must be supplied to evaporate this water? Standard enthalpy of vapourisation of water is 40.79 kJ mol^-1 .

Calculate the entropy change in surrounding when 1.0 mol of H_2O(l) is formed under standard conditions. Given Delta_fH^o = -286 kJ mol^-1.