Question

${}_{17}^{35}Cl$ and ${}_{17}^{37}Cl$ are two isotopes of chlorine in mass ratio of $3:x$, where $x$ $=$ ________.

Answer 1

Formula of average atomic mass is:

$=\frac{A_1{X}_1+A_2{X}_2}{X_1+X_2}$

$=\frac{35\times 3+37\times x}{3+x}=35.5$

$x=1$