Question

Chlorine consists of $75\%$ Chlorine-$35$, $35\%$ and $25\%$of Chlorine-$37$. Calculate the average atomic mass.

Answer 1

Step 1: Given data

Percentage of Chlorine-$35=75\%$

Percentage of Chlorine-$37=35\%$and $25\%$

Step 2: Calculating Average atomic mass

Average atomic mass$=\frac{{\mathrm{P}}_1{\mathrm{A}}_1+{\mathrm{P}}_2{\mathrm{A}}_2}{{\mathrm{P}}_1+{\mathrm{P}}_2}$ where P₁ and P₂ are the percentages of isotopes and A₁ and A₂ is the Atomic masses.

Average atomic mass

$$\begin{gathered} =\frac{0.75\times 35+0.35\times 37+0.25\times 37}{0.75+0.25+0.35} \\ =35.8 \end{gathered}$$

Therefore, the average atomic mass$=35.8\mathrm{g}{\mathrm{mol}}^{-1}$