Question

1 mole of methanol when burnt in excess of ${{O}_{2}}$gives out 723 KJ of heat. 1mole of ${{O}_{2}}$is used what will be the amount of heat evolved:
A. 723 KJ
B. 924 KJ
C. 482 KJ
D. 281 KJ

Answer 1

Methanol is represented by molecular formula $C{{H}_{3}}OH$in which alcoholic group is present due to which prefix ol is given to the compound. When methanol reacts with oxygen then the reaction proceeds is exothermic in nature i.e. a large amount of heat is produced.

Complete answer:
Reaction of the above equation can be shown as:
$C{{H}_{3}}OH+1.5{{O}_{2}}\to C{{O}_{2}}+2{{H}_{2}}O+energy$
Reaction shows that 1.5 mole of oxygen atoms are required for combustion of $C{{H}_{3}}OH$
1.5 mole of ${{O}_{2}}$= 1 mole of $C{{H}_{3}}OH$
Let us suppose, 1 mole ${{O}_{2}}$= x
$x=\dfrac{1}{1.5}=0.6667$mole of $C{{H}_{3}}OH$
1 mole of $C{{H}_{3}}OH$with excess ${{O}_{2}}$= 723 KJ
0.667 mole of $C{{H}_{3}}OH$with excess ${{O}_{2}}$= y
$y=\dfrac{723\times 0.667}{1}=482KJ$

Hence we can say that 482 KJ heat is evolved i.e. option C is the correct answer.

Note:
Combustion is the process in which a substance burns in the presence of Oxygen and gives heat and light during the process. Combustion always takes place in the presence of oxygen. Combustion is classified into two types; complete combustion and incomplete combustion.