Question

At room temperature (27${}^0$ C) the rms speed of the moleculesof certain diatomic gas is found to be 1920 ms${}^{-1}$ then the molecule is:

• A. $H_2$
• B. $F_2$
• C. $O_2$
• D. $C{l}_2$

Answer 1

The correct option is A $H_2$

Let the room temperature is $T={27}^{0}C=27+273=300K$

Now, $V_{rms}=\sqrt{\frac{3RT}{m}}$

$\Rightarrow M=\frac{3RT}{V_{rms}^2}$

By putting the value we get,

$M=\frac{3\times 8.314\times 300}{{1920}^2}=2\times {10}^{-3}kg=2g$

Thus, it is an Hydrogen.