Question

0.16 g methane was subjected to combustion at 27°C in bomb calorimeter. The temperature of the calorimeter system rises by 0.5°C. Calculate the heat of combustion of methane at constant volume. The thermal capacity of calorimeter system is 17.7 kJ K^-1.

Answer 1

Given: m = 0.16,  ΔT = 0.5°C,  

            Q = 17.7,  M = 16 {for CH₄}

So, ΔU = (Q x ΔT x M) / m

             = (17.7 x 0.5 x 16) / 0.16

             = 885 kJ/mol

       ΔU = -885 kJ/mol.

[Since heat is liberated in combustion]