Question

At NTP, $10{\text{L}}$of ${{\text{H}}_2}{\text{S}}$ gas reacted with $10{\text{L}}$ of ${\text{S}}{{\text{O}}_2}$ gas. The volume of gas, after the reaction is complete, would be:
A. ${\text{5L}}$
B. $10{\text{L}}$
C. $15{\text{L}}$
D. $20{\text{L}}$

Answer 1

Hint: A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound. Volume of a gas is usually measured at NTP. At NTP, one mole of any gas occupies a volume of $22.4{\text{L}}$.

Complete step by step answer:
Avogadro’s law states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles. Molar volume of a gas is $22.4{\text{L}}$.
The balanced chemical reaction is given below:
$2{{\text{H}}_2}{\text{S}} + {\text{S}}{{\text{O}}_2} \to 2{{\text{H}}_2}{\text{O + 3S}}$
Here, $2{\text{mol}}$ of ${{\text{H}}_2}{\text{S}}$ is reacted with $1{\text{mol}}$ of ${\text{S}}{{\text{O}}_2}$ producing $2{\text{mol}}$ of water molecule and $3{\text{mol}}$ of sulfur. Mole is used to measure the amount of gases. The mass of one mole of any gas is equal to the molecular mass in grams.
i.e. $2{\text{mol}}$ of ${{\text{H}}_2}{\text{S}}$ has a volume of $2 \times 22.4{\text{L}}$ at NTP.
i.e. $2{\text{mol}}$ of ${{\text{H}}_2}{\text{S}}$ has a volume of $44.8{\text{L}}$ at NTP.
$22.4{\text{L}}$ of ${\text{S}}{{\text{O}}_2}$ gas reacts with $44.8{\text{L}}$ of ${{\text{H}}_2}{\text{S}}$.
$1{\text{L}}$ of ${\text{S}}{{\text{O}}_2}$gas reacts with $\dfrac{{22.4{\text{L}}}}{{44.8{\text{L}}}}$ of ${{\text{H}}_2}{\text{S}}$.
$10{\text{L}}$ of ${\text{S}}{{\text{O}}_2}$ reacts with $\dfrac{{22.4{\text{L}}}}{{44.8{\text{L}}}} \times 10{\text{L = 5L}}$ of ${{\text{H}}_2}{\text{S}}$.

So, the correct answer is Option A.

Additional Information:
One mole has an Avogadro number of particles in it. Mole is the measure of the amount of particles in matter. Molar mass of a substance is the mass of one mole of the substance. It is numerically equal to the atomic mass or formula mass.

Note:
The volume of a gas varies with temperature and pressure. Thus the molar volume of a gas at STP is $22.4{\text{L}}$. The standard temperature is $273{\text{K}}$ and standard pressure is $1{\text{atm}}$. Molar volume of any gas is used as a conversion when calculating quantities of gases in chemical changes.