Calculate the pressure in mm of mercury exerted by hydrogen if the number of molecules per cubic cm is 6.8*10^(15) and the root mean square speed of the molecules is 1.9*10^3 m/s
Comment on the effect of a pressure of this magnitude in a cathode tube.

I calculated the number of molecules per cubic meter is 6.8*10^(15)*1000000=6.8*10^(21)
then I used p=(1/3)nm<c^2>
where n is molecules per unit volume, <c^2> is the r.m.s. speed, and m is the mass of one molecule.
relative molecular mass of hydrogen is given as 2.02.
I plugged these values and got the pressure in Pa, then converted it to mmHg. Pa pressure=1.65*10^(28) and mmHg pressure then is 1.23*10^(26)
Answer is 0.21mmHg so my answer is way far off. where have i gone wrong?

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To each his own.

Is that you have to convert the per cubic cm to per cubic m?

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Good results were achieved and the new task is to become a good doctor.

yes, i converted from molecules per cubic cm to molecules per cubic meter.

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To each his own.

I find out now, it's that you haven't divided the answer by avogadro's constant

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Good results were achieved and the new task is to become a good doctor.

I can't get the answer. I find the pressure in pascals, then divide that by the avogadro constant? then i convert it to mmHg?

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To each his own.

Let me use your answer.
1.23*10^(23)mmHg/6.02X 10^23
=0.20mmHg

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Good results were achieved and the new task is to become a good doctor.

I'm sorry, i made a mistake in the number its 1.23*10^(26). so i can't get the answer.
How would you do it?

__________________
To each his own.