Question

A 295-mL flask contains pure helium at a pressure of 747 torr . A second flask with a volume of 480 mL contains pure argon at a pressure of 717 torr.

A.) If the two flasks are connected through a stopcock and the stopcock is opened, what is the partial pressure of helium?

PHe = ??? torr      

B.) If the two flasks are connected through a stopcock and the stopcock is opened, what is the partial pressure of argon?

PAr = ??? torr

C.) If the two flasks are connected through a stopcock and the stopcock is opened, what is the total pressure?

Ptotal =?? torr

Answer 1

first consider helium :

initially

pressure = 747

volume = 295 ml

now

both the flasks are connected

no reaction took place

so

amount of helium remians

also

the tempertaure is constant

but

the volume chages

final volume = 295 + 480

final volume = 775 ml

now

PV = nRT

at constant n and T

P1V1 = P2V2

so

747 x 295 = P2 x 775

P2 = 284.34

so

the new partial pressure of helium is 284.34 torr

b) similarly for Argon

P1V1 = P2V2

717 x 480 = P2 x 775

P2 = 444.08

so

the partial pressure of Argon is 444.08 torr

C)

now

total pressure = PHe + PAr

total pressure = 284.34 + 444.08

total pressure = 728.42

so

the total pressure is 728.42 torr