1. Question 49
The combustion of .1584g benzoic acid increases the temperature of a bomb calorimeter by 2.54°C. Calculate the heat capacity of this calorimeter. (The energy released by combustion of benzoic acid is kJ/g.) A g sample of vanillin (C8H8O3) is then burned in the same calorimeter, and the temperature increases by 3.25°C. What is the energy of combustion per gram of vanillin? Per mole of vanillin?

2. To find the kJ of .1584g:
26.42kJ/g x .1584g = 4.18kJ/.1584g
Next divide by the change in temp.:
4.18kJ / 2.54°C = 1.65kJ/°C
Therefore, the heat capacity of the calorimeter is kJ/°C

3. Use the equation: ΔT x heat capacity of calorimeter = Energy released by reaction.
3.25°C x 1.65kJ/°C = kJ
Then divide by the number of grams to find kJ/g:
5.3625kJ/.2130g = 25.18kJ/g

4. Next multiply by the molar mass to find the kJ/mol:
25.18kJ/g x 152g/mol = kJ/mol