Question

How many molecules are there in $1\text{liter}$ of any gas at STP?

Answer 1

Step 1: Given information

• The volume of gas is $1\mathrm{L}$.

Step 2: Expression for the calculation of the number of molecules in $\text{V}$ L of gas at STP

• At STP, the volume occupied by one mole of an ideal gas is $22.4\text{L}$.
• The expression for the calculation of the number of molecules in $\text{V}$ L of gas at STP is as follows

$\text{Number of molecules present in V liters of gas at STP=}\frac{{\text{Volume of gas in liters×6.022×10}}^{23}}{22.4\text{liters}}$

Step 3: Calculate the number of molecules in $1\mathrm{L}$ of gas at STP

$$\begin{gathered} \text{Number of molecules present in 1 liters of gas at STP}=\frac{{\text{1 liters×6.022×10}}^{23}\text{molecules}}{22.4\text{liters}}=0.268{\times 10}^{23}\text{molecules} \\ =2.68{\times 10}^{22}\mathrm{molecule}\text{s} \end{gathered}$$

Thus, $2.68{\times 10}^{22}\mathrm{molecule}\text{s}$ are there in $1\text{liter}$ of any gas at STP.