Question

30 mL of hydrogen and 20 mL of oxygen react to give water. What is left at the end of the reaction?

Answer 1

$\underset{\text{2 volume}}{2H_2}+\underset{\text{1 volume}}{O_2}\to H_{2}O$

$2$ volume $H_2$ reacts with $1$ volume of $O_2$ to give $2$ mol of $H_{2}O$ .

$30mL$ of $H_2$ reacts with $15mL$ of $O_2$ to give $H_{2}O$ .

Here, $H_2$ is the limiting reactant.

Volume of $O_2$ left unreacted $=20-15=5mL$