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

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

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