Question

A volume of 10 ml hydrogen requires 25 ml air for complete combustion. The volume percent of ${N_2}$ in air is __________.
A.20%
B.80%
C.79%
D.5%

Answer 1

A combustion reaction is a class of chemical reactions. It is referred to as burning. The process of combustion usually occurs in the presence of oxygen. The material used must be combustible and an oxidizer to form an oxidized product. Here, in an oxidation process, the oxidizing agent takes the electron from an oxidizable substance, thereby itself becoming reduced.

Complete step by step answer:
Combustion is an exothermic reaction, it produces heat, the temperature change is not noticeable. Usually, a combustion reaction involves a hydrocarbon and oxygen, when ignited it releases carbon dioxide and water.
The combustion reaction is as follows:
${H_2} + \dfrac{1}{2}{O_2}\xrightarrow{\Delta }{H_2}O$
$\Rightarrow$As per the reaction, for 10ml of hydrogen, 5ml of oxygen is required for combustion
$\Rightarrow$As per the question, for 10 ml of hydrogen, 25ml of air is needed
$\Rightarrow$For 25ml of air, 5ml would be the air volume
$\Rightarrow$Hence, the difference between the volume of air and water would determine the volume of ${N_2}$
$\Rightarrow$Volume of ${N_2}$ in 25ml air = 25-5 = 20ml of ${N_2}$
$\Rightarrow$The percentage of ${N_2}$ in air = $\dfrac{{20}}{{25}}X100$= 80%
$\Rightarrow$Therefore, 80% of the percentage volume of ${N_2}$ in air.
$\Rightarrow$Thus, option B is the right answer.
A volume of 10 ml hydrogen requires 25 ml air for complete combustion. The volume percent of ${N_2}$ in air is 80%.

Note:
The material can either be completely combustible and is relatively called complete combustion or clean combustion or they can be incompletely combustible and are called incomplete combustion or dirty combustion. An example of complete combustion is burning a wax candle. Whereas, an example of incomplete combustion is the incomplete burning of fossil fuels. Incomplete combustion produces carbon monoxide and carbon dioxide.