# At constant pressure,hydrogen is having temperature of $327^{\large\circ}C$.Till what temperature is it to be cooled such that the rms velocity of its molecules becomes half of the earlier values

$\begin{array}{1 1}(A)\;123^{\large\circ}C\\(B)\;-123^{\large\circ}C\\(C)\;-100^{\large\circ}C\\(D)\;0^{\large\circ}C\end{array}$

$\sqrt{\large\frac{T_1}{T_2}}=$$2=\sqrt{\large\frac{600}{x}} x=150K$$=-123^{\large\circ}C$
Hence (B) is the correct answer.