RMS velocity of oxygen molecules at NTP is $0.5 \mathrm{~km} / \mathrm{s}$. The RMS velocity for the…

RMS velocity of oxygen molecules at NTP is $0.5 \mathrm{~km} / \mathrm{s}$. The RMS velocity for the hydrogen molecule at NTP is
  1. $4 \mathrm{~km} / \mathrm{s}$
  2. $2 \mathrm{~km} / \mathrm{s}$
  3. $3 \mathrm{~km} / \mathrm{s}$
  4. $1 \mathrm{~km} / \mathrm{s}$

Solution

RMS velocity of molecules at NTP $v_{\mathrm{rms}}=\sqrt{\frac{3 R T}{M}}$ RMS velocity of oxygen molecules at NTP $\left(v_1\right)=\sqrt{\frac{3 R T}{M_1}}=0.5 \mathrm{~km} / \mathrm{s}$ RMS velocity of hydrogen molecules at NTP $\begin{aligned} & \left(v_2\right)=\sqrt{\frac{3 R T}{M_2}} \\ & \therefore \quad \frac{v_1}{v_2}=\sqrt{\frac{M_2}{M_1}} \\ & \Rightarrow \quad \frac{0.5}{v_2}=\sqrt{\frac{2}{32}} \\ & \Rightarrow \quad \frac{0.5}{v_2}=\frac{1}{4} \\ & \Rightarrow \quad v_2=2 \mathrm{~km} / \mathrm{s} \\ & \end{aligned}$

Asked in: MHT CET Full Test 9

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