Question

Neon has two isotopes, ${}^{20}Ne$ and ${}^{22}Ne$. If atomic weight of Neon is 20.2, then the ratio of the relative abundances of the isotopes is:

• A. 1 : 9
• B. 9 : 1
• C. 1 : 7
• D. 7: 1

Answer 1

Answer: (B)

9 : 1

Let, the $w\%$ of ${}^{20}Ne=x$

$w\%$ of ${}^{22}Ne=100-x$

$20.2=\frac{x\times 20+(100-x)\times 22}{100}$

$2020=20x+2200-22x$

$2x=2200-2020=180$

$x=90\%$

$\therefore$ $w\%$ of ${}^{20}Ne=90\%$

$w\%$ of ${}^{22}Ne=10\%$

The ratio of the relative abundances of the isotopes is:

$\therefore$ ${}^{20}Ne$ : ${}^{22}Ne$

$=9:1$

Hence, option B is correct.