Question

Calculate the number of molecules in $3.65\text{g}$ of $\mathrm{HCl}$ gas. Take Avogadro's number as $6\times {10}^{23}$.

Answer 1

Step 1: Given information

• $3.65\text{g}$ of hydrogen chloride $\left(\mathrm{HCl}\right)$
• Avogadro's number is $6\times {10}^{23}$

Step 2: Calculation of molecular weight of hydrogen chloride

The molecular weight of hydrogen chloride$=\left(1+35.5\right)\mathrm{g}\text{=36.5 g}$

Step 3: Calculation of the number of molecules of hydrogen chloride

$36.5\text{g}$of $\mathrm{HCl}$ contains $6\times {10}^{23}$ molecules

$3.65\text{g}$ of $\mathrm{HCl}$ contains $\frac{6\times {10}^{23}}{36.5}\times 3.65{\text{=6×10}}^{22}\text{molecules}$

Hence, the number of molecules in $3.65\text{g}$ of $\mathrm{HCl}$ gas is equal to ${\mathrm{6\times 10}}^{22}\text{molecules}$.