States of Matter - Result Question 67
67. At $400 K$, the root mean square (rms) speed of a gas $X$ (molecular weight $=40$ ) is equal to the most probable speed of gas $Y$ at $60 K$. The molecular weight of the gas $Y$ is
(2009)
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Answer:
Correct Answer: 67. (4)
Solution:
$\text { Given, } u _{rms} =u _{mps} $
$\Rightarrow \sqrt{\dfrac{3 R T}{M(X)}}=\sqrt{\dfrac{2 R T}{M(Y)}} $
$\Rightarrow \dfrac{3 R \times 400}{40} =\dfrac{2 R \times 60}{M(Y)} $
$\Rightarrow M(Y) =4$
BETA
