The enthalpy of combustion of benzoic acid (c6h5cooh) is commonly used as the standard for calibrating constant-volume bomb calorimeters; its value has been accurately determined to be −3226.7 kj/mol. when 3.1007 g of benzoic acid are burned in a calorimeter, the temperature rises from 21.84°c to 24.67°c. what is the heat capacity of the bomb? (assume that the quantity of water surrounding the bomb is exactly 2250 g.)

28.96 kJ/°C

We are given;

We are required to find the heat capacity of benzoic acid;

Moles = Mass ÷ molar mass

Molar mass of benzoic = 122.12 g/mol

Therefore;

Moles = 3.1007 g ÷ 122.12 g/mol

          = 0.0254 moles

Heat change for 1 mole = 3226.7 kJ

Moles of Benzoic acid = 0.0254 moles

But;

Specific heat capacity × ΔT = Moles × Heat change

  cΔT = nΔH

Therefore;

Specific heat capacity,c = nΔH ÷ ΔT

                                     = (3226.7 kJ × 0.0254 moles) ÷ 2.83°C

                                    = 28.96 kJ/°C

Therefore, the specific heat capacity of benzoic acid is 28.96 kJ/°C