Question

${}^{35}Cl$ and ${}^{37}Cl$ are the two isotopes of chlorine, in the ratio $3:1$ respectively. If the isotope ratio is reversed the average atomic mass of chlorine will be:

• A. $35.0u$
• B. $35.5u$
• C. $36.0u$
• D. $36.5u$

Answer 1

The correct option is D $36.5u$

Given data

${}^{35}Cl\to 25$ percent $\to x_1$

${}^{37}Cl\to 75$ percent $\to x_2$

Atomic mass $p_1=35$

Atomic mass $p_2=37$

Average atomic mass $=\frac{p_1{x}_1+p_2{x}_2}{p_1+p_2}$

$=\frac{35\times 25+37\times 75}{100}$

$=36.5u$