Posted by **Annabella** on Wednesday, December 8, 2010 at 8:47pm.

Given 175 liters of SO3 at 800 torr and 100 degrees C, find the volume at STP, give the mass of the sample and give the number of molecules in the sample.

Can somebody please explain how I figure this out? I'm so lost. :{

- Chemistry -
**DrBob222**, Wednesday, December 8, 2010 at 8:58pm
I would use

(P1V1/T1) = (P2V2/T2) and solve for V2 at STP.

Then use PV = nRT to solve for n = number of moles of the gas. Since n = grams/molar mass, you know n and molar mass, one can solve for grams.

Finally, you know 1 mole of anything will contain 6.022E23 molecules. Use that piece of information to calculate the number of molecules.

- Chemistry -
**Annabella**, Wednesday, December 8, 2010 at 9:17pm
Thank you SOO much~! :D

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