Question

A 0.3423 g sample of pentane, C5H12, was burned in a bomb calorimeter. The temperature of the calorimeter
and the 1.000 kg of water contained therein rose from 20.22°C to 22.82°C. The heat capacity of the
calorimeter is 2.21 kJ/°C. The heat capacity of water = 4.184 J/g·°C. What is the heat of combustion, in
kilojoules, per gram of pentane?

I'm confused on number 6 on the take home test. in this problem are we going to use the heat capacity of calorimeter is 2.21kJ/c. I'm confused on how to set this problem up
1)I converted 1.000kg in to grams= 1000g
2) I used q=m*c* the change in T
1000g*(4.184J/g* C)*(22.82-20.22) =10460 J
This is where I get stuck at and i'm not sure if i set the problem up right. can you explain to me if i'm doing it right, and/or show me how to set this problem up?

Answer 1

This sounds right to me! Next step to find kJ per gram, would be to convert your J to kJ, and divide by the amount of grams given. This is odd, however, since normally these problems want kJ per mole, not gram. I hope this helps!

Answer 2

It appears to me you have accounted for only a part of the heat.
q = [mass x specific heat x (Tfinal-Tintial)] + [Ccal*(Tfinal-Tinitial)]
The first term takes care of the heat gain in the water and the second term takes care of heating the calorimter.