Transcript Slide 1
Hydrogen gas was collected by the downward
displacement of water. A volume of 600.0 mL of gas
was collected at 25.0 oC and 740.0 torr. What volume
will the “dry” hydrogen occupy at STP if the vapor
pressure at 25.0 oC is 23.8 torr. ?
First find the pressure of the “dry” hydrogen gas by
subtracting the H2O vapor pressure.
P total= PH2+ PH2O
740.0 torr = PH2 + 23.8 torr
740.0 - 23.8 = 716.2 torr = PH2
Use combined gas law to find the volume at
STP (273 K & 1 atm = 760 torr)
P1 V1 = P2 V2
(716.2 torr)(600ml) = (760)V2
V2 = 518 mL