Question

In a constant volume calorimeter, 3.5 g of a gas with molecular weight 28 was burnt in excess oxygen at 298.0 K. The temperature of the calorimeter was found to increase from 298 K to 298 K due to the combustion process. Given that the heat capacity of the calorimeter is 2.5 kJ $K^{- 1}$ , the value for the enthalpy of combustion of the gas is

• A. 90 kJ $mol^{- 1}$
• B. 9 kJ $mol^{- 1}$
• C. 18 kJ $mol^{- 1}$
• D. 6 kJ $mol^{- 1}$

Answer 1

Answer: (B)

Energy released by combustion of 3.5 g gas

$=2.5\times \left(\right.298.45-298) \, kJ$

Energy released by 1 mole of gas $=\frac{2.5 \times 0.45}{3.5 / 28}=9 \, kJmol^{- 1}$