Question

Calculate the heat of combustion (in KJ) of

methane from the following data

i) C (graphite) + 2H${}_2$(g) $\to$ CH${}_4$ (g),$\Delta$H = -74.8 kJ

ii) C (graphite) + O${}_2$ (g) $\to$ CO${}_2$ (g),$\Delta$H = -393.5 kJ

iii) H${}_2$ (g) +1/2O${}_2$(g)$\to$ H${}_2$O$\left(l\right)$ , $\Delta$H = -286.2 KJ.

• A. -891.1
• B. -816.3
• C. -965.9
• D. -1040.7

Answer 1

The correct option is A -891.1

$C{H}_4+2O_2\to C{O}_2+2H_{2}O$
(ii) + 2 (iii) - (i)
$\Delta H=$ - 393.5 + 2 x (-286.2) + 74.80
$\Delta H=$ - 891.1 KJ