The heat liberated when 1.89g of benzoic acid is burnt in a bomb calorimeter at 25 °C and it increases the temperature of 18.94 kg of water by 0.632 °C. if the specific heat of water at 25 °C is 0.998 cal/g- °C, the value of the heat of combustion of benzoic acid is

Given: weight of benzoic acid = 1.89 g; Temperature of bomb calorimeter = 25 °C = 298 K; Mass of water (m) = 18.94 kg = 18940 g; Increase in temperature 0.632 T C and specific heat of water (s) = 0.998 cal/g-deg. We know that, heat gained by water or heat liberated by benzoic acid (Q) = m sΔT = 18940 × 0.998 × 0.632 = 11946.14 cal Since 1.89 g of acid liberates 11946.14 cal of heat, therefore heat liberated by 122 g of acid 11946.14 122 1.89 x 771126.5 771.12 cal kcal (where 122 g is the molecular weight of benzoic acid)