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A glass bulb of 1 litre capacity contains \small 2\times10^{21}  molecules of nitrogen exerting pressure of \small 7.57\times 10^3Nm^{-2} . After calculating the root mean square speed (in m/sec) and the temperature of gas molecules finally calculate n_{mp} for these molecules at this temperature, if the ratio of  \dpi{100} \small u_{mp}  to \small u_{rms} is 0.82.

Option: 1

40.52


Option: 2

503.56


Option: 3

405.26


Option: 4

400.43


Answers (1)

best_answer

We have given:

P=7.57\times10^3 Nm^{-2}

V=10^{-3}m^3

And, n=(2\times 10^{21})/(6.023\times 10^{23})

Now, we know the ideal gas equation,
PV = nRT

\\\mathrm{7.57\: x\: 10^{3}\: x\: 10^{-3}\: =\: \frac{2\: x\: 10^{21}}{6.023\: x\: 10^{23}}\: x\: 8.314\: x\: T}

 

Thus, T = 274.2K
Now, again we know that

u_{rms}=\sqrt{\frac{3RT}{M}}

u_{rms}=\sqrt{\frac{3\times 8.314 \times 274.2}{28\times10^{-3}}}

u_{rms}=494.22m/sec

Now, as we have given:
u_{mp}=0.82u_{rms}
Thus, u_{mp}=0.82\times 494.22
Hence, u_{mp}=0.82\times 494.22=405.26m/sec
 

Posted by

Rakesh

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