Question

Find ΔErxn for the combustion of C10H8 in kJ/mol. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 4.947 kJ/∘C .

When 1.318 g of C10H8 undergoes combustion in a bomb calorimeter, the temperature rises from 26.04 ∘C to 49.29 ∘C.

Answer 1

The balanced equation would be:

C10H8 (s) + 12 O2 (g) ---> 10 CO2 (g) + 4 H2O (g) + heat

From the data, the number of moles of Naphthalene used is:

1.318 g / 128.2 g/mol = 0.01028 moles of C10H8

The change in temperature is:

49.29 °C - 26.04 °C = 23.25 °C

If only the calorimeter changed temperature (no outside loss or water jacket), then the change in heat energy is:

23.25 °C * 4.947 kJ/ °C = 115.01775 (ΔE)

To get the ΔErxn (per mole), divide the ΔE above by the moles of C10H8 used.

ΔErxn (per mole)= 115.01775 / 0.01028 moles = 11188.4970 kJ/mole.