Question

A gas (Molar mass = 280 g mol-1) was burnt in excess O2 in a constant volume calorimeter and during combustion the temperature of calorimeter increased from 298.0 K to 298.45 K. If the heat capacity of calorimeter is 2.5 kJ K-1 and enthalpy of combustion of gas is 9 kJ mol-1 then amount of gas burnt is __________g. (Nearest Integer).

Answer 1

The correct answer is: 35.

ΔU = CΔT
= 2.5 × 103 × 0.45
= 1.125 kJ
Considering ΔH ≈ ΔU
ΔH = 9kJ/mol≈ΔU
∴ Mass of gas burnt = $\frac{1.125}{9}×280$
= 35g