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Question: Answered & Verified by Expert
Increasing order of rms velocities of $\mathrm{H}_{2}, \mathrm{O}_{2}, \mathrm{~N}_{2}$ and $\mathrm{HBr}$ is
ChemistryStates of MatterBITSATBITSAT 2013
Options:
  • A $\mathrm{H}_{2}>\mathrm{O}_{2}>\mathrm{N}_{2}>\mathrm{HBr}$
  • B $\mathrm{HBr}<\mathrm{O}_{2}<\mathrm{N}_{2}<\mathrm{H}_{2}$
  • C $\mathrm{H}_{2}>\mathrm{N}_{2}<\mathrm{O}_{2}>\mathrm{HBr}$
  • D $\mathrm{HBr}>\mathrm{N}_{2}<\mathrm{O}_{2}<\mathrm{H}_{2}$
Solution:
1814 Upvotes Verified Answer
The correct answer is: $\mathrm{HBr}<\mathrm{O}_{2}<\mathrm{N}_{2}<\mathrm{H}_{2}$
RMS velocity of molecules depends on mass. If mol. wt. increases, rms velocity of melocules decreases. $\mathrm{rms} \propto \frac{1}{\sqrt{\mathrm{m} \cdot \mathrm{wt}}}$

The order of increasing $\mathrm{m} . \mathrm{wt}$. is

$\mathrm{H}_{2}<\mathrm{N}_{2}<\mathrm{O}_{2}<\mathrm{HBr}$

Order of $V_{\mathrm{mx}}$ of molecules. $\mathrm{HBr}<\mathrm{O}_{2}<\mathrm{N}_{2}<\mathrm{H}_{2}$

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