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* \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* (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=-(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}}=(1.608g)/(164.22g/mol)=0.009792mole`

`\Delta H=-(70.43kJ)/(0.009792mole)=-7193kJ/mole`

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