Question

1 $mol$ of methanol when burnt in excess of $O_2$ gives out $723kJ$ of heat. If $1mol$ of $O_2$ is used what will be the amount of heat evolved:

• A. $723kJ$
• B. $924kJ$
• C. $482kJ$
• D. $241kJ$

Answer 1

The correct option is C $482kJ$

Solution:- (C) $482kJ$

Combustion of methane-

${C{H}_{3}OH}_{\left(g\right)}+\frac{3}{2}{O}_2⟶C{O}_2+2{H_{2}O}_{\left(l\right)};\Delta H=-723kJ/mol$

From the above reaction-

Heat evolved when $1.5$ mole of oxygen used $=723kJ/mol$

Therefore, heat evolved when $1$ mole of oxygen used $=\frac{723}{1.5}=482kJ/mol$

Hence the heat evolved when $1$ mole of oxygen used is $482kJ/mol$.