5.00 g of carbon were adiabatically burned to CO2 in a 2.00 kg copper calorimeter which contained 2.50 kg of water. The temperature increased by 14.1 °C.

Specific heats: copper, 0.385 J K⁻¹ g⁻¹; water, 4.184 J K⁻¹ g⁻¹.

a) Determine the heat of combustion of carbon ignoring any heat absorbed by the calorimeter.

b) Now determine the heat of combustion considering the heat absorbed by the calorimeter.

A. - 163.96kJ

B. - 158.34kJ

Explanation:

Heat of combustion is the heat released when an element with oxygen at stp.

Reaction for the combustion of carbon:

C (s) + O2 (g) - -> CO2 (g)

Enthalpy heat of combustion, C (using Hess law) = - 393.5 kJ/mol

m = 5g

Molecular weight = 12 g/mol

No of moles = mass/molecular weight

= 5/12

= 0.417mol

DH = - 393.5 * 0.417

= - 163.96 kJ

B. Heat absorbed by the calorimeter = heat evolve by combustion

= mCH2ODT + mCcDT

Where CH2O is the specific heat capacity of the water in the calorimeter

Cc is the specific heat capacity of copper calorimeter

= (2500*4.184*14.1) + (2000*0.385*14.1)

= - 158343J

= - 158.34kJ