The heat is liberated when 1.89 ~g 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 -deg, then value of the heat of combustion of benzoic acid is

Step-by-step solution

Mass of benzoic acid =1.89 ~g Temperature of bomb calorimeter =25^ C =298 ~K Mass of water (m)=18.94 ~kg =18940 ~g [ncrease in temperature ( t)=0.632^ C Specific heat of water (s)=0.998 cal / g - deg Heat gained by water or heat liberated by benzoic acid (Q)=m s t=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 (mol. aligned & wt. of benzoic acid) of acid = 11946.14 122 1.89 & =771126.5 cal 771.1 kcal aligned