how would you figure this out?

Question

if 500 mL of hydrogen are colected over water at 20 degrees c and 745 torr, what will the volume of the dry gas be at STP?

Answer 1

You can use (P1V1)/T1 = (P2V2)/T2
Use for P1 = 745 - vapor pressure of water at 20 degrees C (which you will find in a table--I'm sure your text has one). V1 is of course 500 mL and you are solving for V2. Don't forget to change T to Kelvin. Post your work if you get stuck.