Answer
$632m/s$
Work Step by Step
We can find the rms velocity of $NH_3$ as follows:
$rms \space of\space NH_3=\sqrt{\frac{3RT}{m}}$
We plug in the known values to obtain:
$rms \space of\space NH_3=\sqrt{\frac{3(8.31)(273)}{0.017}}$
$rms \space of \space NH_3=632m/s$
