Question

What is the mass of $22.4{\text{dm}}^3$ of the following gas at STP?

(b) hydrogen sulfide

Answer 1

Step 1: Given information

$22.4{\text{dm}}^3$ of hydrogen sulfide $\left({\mathrm{H}}_2\mathrm{S}\right)$

Step 2: STP

• STP indicates Standard Temperature and Pressure.
• Temperature =$0^{°}\text{C}$
• Pressure=$1\text{atm}$
• The volume of an ideal gas at STP is $22.4\text{L}$.

Step 3: Calculation of molecular mass

The molecular mass of hydrogen sulfide

$$\begin{gathered} =2\text{H+S} \\ =\left(2\times 1+32\right)\text{g} \\ =34\text{g} \end{gathered}$$

Step 4: Calculation of required mass of hydrogen sulfide

"The molar volume or gram molecular volume represents the volume occupied by one gram molecular mass of a given gas at STP and it is equal to $22.4\text{L}$".
Therefore, $22.4\text{L}$ of volume is occupied by $\text{34 g}$ of ${\mathrm{H}}_2\mathrm{S}$ at STP.

Since, $22.4{\text{dm}}^3$ is equal to $22.4\text{L}$ .

Hence, the mass of $22.4{\text{dm}}^3$ of hydrogen sulfide gas at STP is $34\text{g}$.