Question

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.

Answer 1

Answer:

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