Question

The aromatic hydrocarbon cymene (C10H14) is found in nearly 100 spices and fragrances, including coriander, anise, and thyme. The complete combustion of 1.608 g of cymene in a bomb calorimeter (Calorimeter = 3.640 kJ/°C) produced an increase in temperature of 19.35°C. How much thermal energy is produced during the complete combustion of one mole of cymene?

Answer 1

Answer : The thermal energy produced during the complete combustion of one mole of cymene is -7193 kJ/mole

Explanation :

First we have to calculate the heat released by the combustion.

$q=c\times \Delta T$

where,

q = heat released = ?

$c$ = specific heat of calorimeter = $3.640kJ/^oC$

$\Delta T$ = change in temperature = $19.35^oC$

Now put all the given values in the above formula, we get:

$q=3.640kJ/^oC\times (19.35)^oC$

$q=70.43kJ$

Thus, the heat released by the combustion = 70.43 kJ

Now we have to calculate the molar enthalpy combustion.

$\Delta H=-\frac{q}{n}$

where,

$\Delta H$ = molar enthalpy combustion = ?

q = heat released = 70.43 kJ

n = number of moles cymene = $\frac{\text{Mass of cymene}}{\text{Molar mass of cymene}}=\frac{1.608g}{164.22g/mol}=0.009792mole$

$\Delta H=-\frac{70.43kJ}{0.009792mole}=-7193kJ/mole$

Therefore, the thermal energy produced during the complete combustion of one mole of cymene is -7193 kJ/mole