Question

When 0.7521 g of benzoic acid was burned in a calorimeter, a temperature rise of 3.60°C was observed. What is the heat capacity of the bomb calorimeter? The heat of combustion of benzoic

Answer 1

Answer : S=1.34 KJ

The complete question is -

When 0.7521 g of benzoic was burned in a calorimeter containing 1000 g of water, a temperature rise of 3.60C was observed. What is the heat capacity of the bomb calorimeter, excluding water? The specific heat of water is 4.184 J/g-C and the heat of combustion of benzoic acid is 26.42 kJ/g. 

On using the formula of $Q_{rxn} = mSt$, where m is mass of benzoic acid and S is specific heat and t is temperature, we ignore S at this stage.

on solving we get,  $Q_{rxn}$ = 0.7521 X 26.42 = 19.870 KJ

We know, $Q_{rxn}$ =$Q_{calorimeter}$ + $Q_{water}$

Sp. heat of water is 4.184 J,

Here $Q_{water}$ = 1000 X 4.184 X 3.6 = 15062.4 J

on multiplying $Q_{rxn}$ X 1000 to convert into J = 19870.42 J

on substituting the values we get, 19870.482 = 15062.4 + $Q_{calorimeter}$, 
hence, $Q_{calorimeter}$= 4808.082,

Substituting in  $Q_{rxn}$ , we get, 4808.082=St ...(ignoring mass as we changed it to J)

t = 3.6, hence we get, S=1335 J/C on dividing by 1000 we get, S=1.34 KJ