We’re being asked to determine the gas that would have the smallest root mean square speed at 100°C.

When calculating for root mean square speed (μ_{rms}), we will use the following equation:

$\overline{){{\mathbf{\mu}}}_{{\mathbf{rms}}}{\mathbf{=}}\sqrt{\frac{\mathbf{3}\mathbf{RT}}{\mathbf{M}}}}$

µ_{rms} = rms speed,

R = 8.314 J/(mol·K)

T = temperature, K

M = molar mass, kg/mol

Which of the following gases will have the smallest root mean square speed at 100°C?

(A) H_{2}O

(B) CH_{4}

(C) N_{2}

(D) O_{2}

(E) Ar

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