Chemestry @
posted by Please help on .
A 27.6ml volume of chlorine gas is collected over water at 23 C and 750 torr. The mass of the gas is 78.4mg. The vapor pressure of water is 21 torr.
a)what is the pressure of the chlorine gas?
b) what volume does the chlorine gas occupy?
c)How many moles of chlorine gas are collected?

a.
total pressure = partial pressure water + partial pressure chlorine.
b.
I don't know what I missed but the problem says you have 27.6 mL I think. In any case, however, you haven't specified the pressure or temperature of if you want the dry gas or wet gas.
c.
Use PV = nRT.
Post your work if you get stuck. 
Thanks I was stuck in the total pressure part I didn't know if I need it to add them up or just use one. thanks for your help I appreciated. this web side is gread thanks

temperature is 296K and Presure is 750 torr and the vapor pressure of the water is 21 torr. thanks for you help

If you want the volume at these conditions then use PV = nRT to determine the number of mols at the conditions cited, then use PV = nRT a second time at the new conditions to determine V.