Question

What will be the amount of heat evolved by burning 10 L of methane under standard conditions? (Given heats of formation of $CH_{4},$ $CO_{2}$ and $H_{2}O$are

$- 76.2, - 398.8and - 241.6kJmol^{- 1}$ respectively)

• A. $805.8kJ$
• B. $398.8kJ$
• C. $359.7kJ$
• D. $640.4kJ$

Answer 1

Answer: (C)

$359.7kJ$

Answer 2

: $CH_{4} + 2O_{2} \rightarrow CO_{2} + 2H_{2}O$

$\Delta H = H_{P} - H_{R}$

}{- \left\lbrack \Delta H_{f}^{o}(CH_{4}) + 2\Delta H_{f}^{o}(O_{2}) \right\rbrack}$$ $= - 398.8 - 2 \times 241.6 - ( - 76.2 + 2 \times 0) = - 805.8kJmol^{- 1}22.4LofCH_{4}$ (1 mole) gives $805.8kJ$ 10 L of $CH_{4}$will give,$\frac{805.8}{22.4} \times 10 = 359.73kJ$