Chemistry
posted by Kellina .
A sample of air was compressed to a volume of 18.0 L. The temperature was 290.0 K, and the pressure was 6.80 atm. How many moles of gas were in the sample?
If the sample had been collected from air at P = 2.0 atm., what was the original volume of the gas (in liters)?
How do I approach this?

#1. PV = nRT and solve for n = mols.
#2. Using n from #1, use PV = nRT and solve for V. 
How many milliliters of ozone gas at at 25.0°C and 1.00 atm pressure are needed to react with 45.00 mL of a 0.300 M aqueous solution of KI

CF2CI2 Mass: 1.02kg what are number of molecules , and moles