Question

The relative atomic mass of an element A is $16.2$ there are two isotopes ${}_8^{16}A$ and ${}_8^{18}A$ of the element. Calculate the percentage of these two isotopes present in the element.

Answer 1

Data:-

Relative atomic mass=$16.2$

Atomic mass of ${}_8^{16}A=16$

Atomic mass of ${}_8^{18}A=18$

Formula:-

Let percentage of Isotope ${}_8^{16}A$ be $⟶x$

$\therefore$ Percentage of Isotope ${}_8^{18}A⟶(100-x)$

Relative atomic weight=$[Atomicweightof{}_8^{16}A\times abundance+Atomicweightof{}_8^{18}A\times abundance]/100$

$\therefore 16.2=\frac{16\times x+18\times (100-x)}{100}=\frac{16x\times 1800-18x}{100}$

$\Rightarrow 16.2\times 100=1800-2x$

$\Rightarrow 1620=1800-2x$

$\Rightarrow 2x=1800-1620$

$\Rightarrow 2x=180$

$\therefore x=90$

$100-x=10$

Percentage of ${}_8^{16}A$ is $90$%

Percentage of ${}_8^{18}A$ is $10$% .