Posted by **Hannah** on Friday, January 13, 2012 at 10:44pm.

Which molecule has the greatest average velocity at 100 degrees celsius.

He, Cl2, Xe, O2, NO2

I used the root mean squared formula but I think I did it wrong. I got Xe as my answer. Is this correct?

- Chemistry -
**DrBob222**, Friday, January 13, 2012 at 11:00pm
From u = sqrt(3RT/M), the largest M will give you the smallest u. The smallest M will give you the largest u.

- Chemistry -
**Hannah**, Friday, January 13, 2012 at 11:12pm
What is RT?

So for He I would do square root 3 times (value of RT) / 1.0079 correct?

- Chemistry -
**DrBob222**, Friday, January 13, 2012 at 11:16pm
R is 8.314

T is temperature.

However, you are asked only for the greatest, not a value. You don't need R or T.

- Chemistry -
**Hannah**, Saturday, January 14, 2012 at 12:40am
so I just have to compare the molar mass of each gas and the smallest is the greatest?

- Chemistry -
**DrBob222**, Saturday, January 14, 2012 at 1:46am
Yes, if the root mean squared velocity is what you are looking for.

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