Question

What is the balanced chemical equation for $C{H_3}OH + {O_2}$ yields for $C{O_2} + {H_2}O$?

Answer 1

Hint: When we balance the equation, we have to make sure that we have the same number of atoms for each kind of element on two sides of the equation. We have to balance the equation using the atoms of carbon, hydrogen and oxygen. We have to balance the atoms of carbon, then balance hydrogen atoms. Finally, we have to balance the atoms of oxygen atoms.

Complete step by step answer:
We have to know that in combustion reactions of alcohols, the products obtained are carbon dioxide in gaseous state and water in liquid state.
We must know that when methanol undergoes complete combustion in the presence of oxygen, the products obtained are carbon dioxide and water.
We can write the chemical equation as,
$C{H_3}OH + O{}_2\xrightarrow{{}}C{O_2} + {H_2}O$
We have to first balance the atoms of carbon. The chemical equation is written as,
$2C{H_3}OH + O{}_2\xrightarrow{{}}2C{O_2} + {H_2}O$
We have to now balance the atoms of hydrogen because the number of hydrogen atoms are lesser than the number of oxygen atoms. So, the chemical equation becomes,
$2C{H_3}OH + O{}_2\xrightarrow{{}}2C{O_2} + 4{H_2}O$
Now let us balance the atoms of oxygen which are remaining.
$2C{H_3}OH + 3O{}_2\xrightarrow{{}}2C{O_2} + 4{H_2}O$
We shall now check if all the atoms are balanced on both sides of the equations.

Atoms	LHS	RHS
C	$2$	$2$
H	$8$	$8$
O	$8$	$8$

From the table above, we can see that all atoms are balanced.
So, we can write the final balanced chemical equation as,
$2C{H_3}OH + 3O{}_2\xrightarrow{{}}2C{O_2} + 4{H_2}O$

Note: We have to know that combustion reactions of alcohols are of two types. The first type of combustion reaction is complete combustion. Incomplete combustion is the second type of combustion. In complete combustion of alcohols, excess oxygen is used for the reaction. The products obtained in gaseous carbon dioxide and water. Incomplete combustion of alcohols, oxygen present is not in sufficient amounts, the products obtained are gaseous carbon dioxide and/or gaseous carbon monoxide and water.