A 260-mL flask contains pure helium at a pressure of 762 torr . A second flask w

ID: 538771 • Letter: A

Question

A 260-mL flask contains pure helium at a pressure of 762 torr . A second flask with a volume of 475 mL contains pure argon at a pressure of 717 torr

Part A

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

Part B

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

Part C

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

volume = 260 mL = 0.260 L

pressure = 762 torr = 1.00 atm

temperature = 298 K

P V = n R T

1 x 0.260 = n x 0.0821 x 298

n1= 0.0106

v2 = 0.475 L

p2 = 717 torr = 0.943 atm

0.943 x 0.475 = n x 0.0821 x 298

n2 = 0.0183

total number of moles = 0.0183 + 0.0106

= 0.0289 mol

P V = n R T

P x 0.735 = 0.0289 x 0.0821 x 298

P = 0.962

total pressure = 731 torr

mole fraction of He = 0.0106 / 0.0289 = 0.367

mole fraction of Ar = 0.633

partial pressure of He = 0.367 x 731

partial pressure of He = 268 torr

partial pressure of Ar = 463 torr

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