The average molar mass of chlorine is $35.5 \mathrm{~g} \mathrm{~mol}^{-1}$. The ratio of ${ }^{35} \mathrm{Cl}$ to ${ }^{37} \mathrm{Cl}$ in naturally occurring chlorine is close to:

JEE Main · 2020 · 06 Sep 2020 · Shift 2 · Some Basic Concepts of Chemistry

The average molar mass of chlorine is

35.5 g mol^{- 1}

. The ratio of

^{35} Cl

^{37} Cl

in naturally occurring chlorine is close to:

Answer: (B)

Let the fraction of

^{35} Cl

x

and of

^{37} Cl

1 - x

. Matching the average mass,

35 x + 37 (1 - x) = 35.5

, gives

- 2 x = - 1.5

, so

x = 0.75

. The two isotopes are thus present in the ratio

^{35} Cl :^{37} Cl = 3 : 1

JEE Main · 2020 · 06 Sep 2020 · Shift 2 · Single correct option