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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ig220

Which of the following statements about the rms speed $u_{rms}$ of an ideal gas are correct?

A $u_{rms}$ of $H X_{2}$ at $100 K$ equals that of $O X_{2}$ at $1600 K$
BDoubling the molar mass at constant $T$ halves $u_{rms}$
C $u_{rms}$ is proportional to $P / d$ , where $d$ is the density
DAt constant pressure, $u_{rms}$ is independent of volume

Answer: A, C

Equal

T / M

:

100/2 = 1600/32 = 50

(A). Doubling

M

divides

u_{rms}

by

2

, not 2 (B wrong).

u_{rms} = 3 P / d

(C). At constant

P

, changing

V

changes

T

for a fixed amount, so

u_{rms}

changes (D wrong).

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