Question

A quantity of 1.922 g of methanol (CH3OH) was burned in a constant-volume bomb calorimeter. Consequently, the temperature of the water rose by 4.20 Ce … lsius. If the heat capacity of the bomb plus water was 10.4 kJ/degree Celsius, calculate the molar heat of combustion of methanol

Answer 1

The formula for calculating the amount of energy or heat released is:

ΔH = C ΔT

where ΔH is heat of combustion, C is heat capacity, while ΔT is change in temperature

ΔH = 8.69 kJ / °C * (5.14°C)

ΔH = 44.67 kJ

Then we calculate the moles of CH3OH which has molar mass of 32.04 g/mol:

moles = 1.922 / 32.04 = 0.05999 mol

SO the molar heat of combustion is:

ΔHm = 44.67 kJ / 0.0599875 mol

ΔHm = 744.60 kJ / mol