Question

In an oven, using $10kg$ coal (assume the coal is $80\%$ carbon in weight), insufficient oxygen is supplied such that $60\%$ of carbon is converted to $C{O}_2$ and $40\%$ carbon is converted to $CO$. The heat generated, when coal is burnt in this fashion would be
Given : $C_{(s)}+O_{2(g)}\to C{O}_{2(g)};\Delta H=-394kJ$
$C_{(s)}+\frac{1}{2}{O}_{2(g)}\to C{O}_{(g)};\Delta H=-111kJ$

• A. $183200kJ$
• B. $187200kJ$
• C. $185200kJ$
• D. $181200kJ$

Answer 1

Answer: (B)

As coal has $80\%$ carbon in weight

weight of carbon in $10kg$ coal $=10\times \frac{80}{100}=8kg=8000g$

As $60\%$ of $C$ is converted to $C{O}_2$ thus wt. of $C$ converted into

$C{O}_2=8000\times \frac{60}{100}=4800g$

and $40\%$ of $C$ to $CO$ thus $wt$. of $C$ converted into $CO$

$=8000\times \frac{40}{100}=3200g$

$12g(1mole)$ of $C$ on combustion liberates $=394kJ$ of heat

$\therefore 4800g$ of $C$ on combustion liberates

$=\frac{394\times 4800}{12}kJ=157600kJ\dots ..(i)$

$12g(1mole)$ of $C$ on combusion liberates $=111kJ$ of heat

$\therefore 3200g$ of $C$ on combustion liberates

$=\frac{111\times 3200}{12}kJ$

$=29600kJ$

Total heat liberated would be

$=157600+29600=187200kJ$