Question

Argon has three isotopes with relative atomic masses of $36,38$ and $40$. Given that the average relative atomic mass of naturally occurring argon is $39.95$. Which of the following statements must be correct?

• A. ${}^{40}Ar$ is less abundant than ${}^{38}Ar$
• B. ${}^{40}Ar$ is more abundant than either ${}^{36}Ar$ or ${}^{38}Ar$.
• C. ${}^{40}Ar{,}^{38}Ar$ and ${}^{36}Ar$ are equally abundant
• D. ${}^{36}Ar$ is more abundant than ${}^{40}Ar$

Answer 1

The correct option is B ${}^{40}Ar$ is more abundant than either ${}^{36}Ar$ or ${}^{38}Ar$.

Here average atomic mass of naturally occuring argon is 39.5 and this value is very close to the 40 in comparison to 36 and 38. So that Argon with relative mass 40 is more abundant than others.