Question

Among the following gases which one has the lowest root mean square speed at ${25}^{\circ }C$ :

• A. $S{O}_2$
• B. $N_2$
• C. $O_2$
• D. $C{l}_2$

Answer 1

The correct option is D $C{l}_2$

Chlorine gas has the lowest root mean square speed at 25${}^{o}C$ as it has highest molar mass (71 $g/mol$)

$V_{\text{rms}}=\sqrt{\frac{3RT}{M}}$

$RMS$ speed is inversely proportional to the square root of molar mass.

Higher is the molar mass of the substance, lower is the root mean square velocity of it.

Hence, the correct option is $\text{D}$