5.00 g of carbon were adiabatically burned to CO2 in a 2.00 kg copper calorimete

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 K1 g1; water, 4.184 J K1 g1.

a) Determine the heat of combustion of carbon ignoring any heat absorbed by the calorimeter. [-147 kJ]

b) Now determine the heat of combustion considering the heat absorbed by the calorimeter. [-158 kJ]

The answers are given to us but I am having trouble bringing all the info together. I know I must somehow incoorporate the equation q=mass*specific heat*delta T

Any help will be greatly appreciated, thank you.

Explanation / Answer

a) heat absorbed by the water(Q) = m*s*DT

m = mass of water = 2.50 kg = 2500 g

s = Specific heat of water = 4.184 j.k-1.g-1

DT = 14.1 c

     Q = 2500*4.184*14.1

       = 147486 joule

   = 147.5 kj

heat of combustion of carbon = heat absorbed by the water(Q)

heat of combustion of carbon = -147.5 kj

b) heat absorbed by the water + calorimeter(Q) = m1*s1*DT + m2*s2*DT

m1 = mass of water = 2.50 kg = 2500 g

s1 = Specific heat of water = 4.184 j.k-1.g-1

DT = 14.1 c

m2 = mass of copper = 2.00 kg = 2000 g

s2 = Specific heat of copper = 0.385 j.k-1.g-1

     Q = 2500*4.184*14.1 + 2000*0.385*14.1

       = 158343 joule

   = 158.34 kj

heat of combustion of carbon = heat absorbed by the water+calorimeter(Q)

heat of combustion of carbon = -158.34 kj

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