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At which temperature the r.m.s. velocity of a hydrogen molecule equal to that of an oxygen molecule at \(47^{\circ} \mat…

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PYQ

At which temperature the r.m.s. velocity of a hydrogen molecule equal to that of an oxygen molecule at \(47^{\circ} \mathrm{C}\) ?

a

\(-73 \mathrm{~K}\)

b

\(4 \mathrm{~K}\)

c

\(20 \mathrm{~K}\)

d

\(80 \mathrm{~K}\)

✓ Correct answer: c)

\(20 \mathrm{~K}\)

Explanation

\(\begin{matrix}{v}_{rms}=\sqrt{\frac{3RT}{M}} \\ \Rightarrow {v}_{rms}\propto \sqrt{\frac{T}{M}}\end{matrix}\)

\[\frac{T_1}{M_1} = \frac{T_2}{M_2}\]

\[T_1 = T_2 \times \frac{M_1}{M_2}\]

Substituting the values:

\[T_1 = 320 \times \frac{2}{32}\]

\[T_1 = 320 \times \frac{1}{16}\]

\[T_1 = 20\ \text{K}\]

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