Question

Find the rms speed of an argon molecule at ${27}^{\circ }C$ (Molecular weight of argon $=40gm/mol$).

• A. $234.2m/s$
• B. $342.2m/s$
• C. $432.2m/s$
• D. $243.2m/s$

Answer 1

The correct option is C $432.2m/s$

The rms speed (u) is related to the temperature (T) and molecular weight (M) by the expression
$u=\sqrt{\frac{3RT}{M}}$
$u=\sqrt{\frac{3\times 8.314J/molK\times (27+273.15)K}{40\times {10}^{-3}kg/mol}}$
$u=432.2m/s$
Hence, the rms speed is 432.2 m/s