Question

$4g$ hydrogen reacts with $20g$ of oxygen to form water. The mass of water formed is:

• A. $24g$
• B. $36g$
• C. $22.5g$
• D. $40g$

Answer 1

The correct option is

B

$22.5g$

$H_2+\frac{1}{2}{O}_2⟶H_{2}O$

Mass-$4g20g$

Moles-$20.625$

$1$ mole of $H_2$ requires $0.5$ moles of $O_2$.

$\therefore$ $1.25$ moles of $H_2$ requires $0.625$ moles of $O_2$

$\therefore$ $O_2$ is a limiting reagent.

$0.5mole{O}_2⟶1mole{H}_{2}O$

$\therefore 0.625mole{O}_2=\frac{1\times 0.625}{0.5}moles{H}_{2}O.$

$=1.25molesof{H}_{2}O$

Therefore, mass of $H_{2}O$ formed $=1.25\times 18=22.5gm$

Hence, option $B$ is correct.