Question

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

(a) ammonia

Answer 1

Step 1: Given information

$22.4{\text{dm}}^3$ of ammonia$\left({\mathrm{NH}}_3\right)$

Step 2: STP

• STP indicates standard temperature and pressure.
• Temperature=$0^{\circ }\text{C}$
• 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 ammonia

=$$\begin{gathered} \text{=N}+3\text{H} \\ =\left(14+3\times 1\right)\text{g} \\ =17\text{g} \end{gathered}$$

Step 4: Calculation of required mass of ammonia $\left({\mathrm{NH}}_3\right)$ at STP

"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 $17\text{g}$ of ammonia at STP.

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

Hence, mass of $22.4{\text{dm}}^3$ of the ammonia gas at STP is $17\text{g}$.