Question

A 275-mL flask contains pure helium at a pressure of 752 torr. A second flask with a volume of 475 mL contains pure argon at a pressure of 722 torr. If the two flasks are connected through a stopcock and the stopcock is opened, what is the partial pressure of each gas and the total pressure?

Answer 1

• Partial pressure He = 276 torr

• Partial pressure Ar = 457 torr

• Total pressure = 733 torr

Step-by-step explanation:

Assuming temperature remains constant, we can use Boyle's law to solve this problem: P₁V₁=P₂V₂.

Once the two flasks are connected and the stopock opened, the total volume is:

• 275 + 475 = 750 mL

Now we use Boyle's law twice, to calculate the new pressure of each gas:

• He ⇒ 752 torr * 275 mL = P₂He * 750 mL

P₂He = 276 torr

• Ar ⇒ 722 torr * 475 mL = P₂Ar * 750 mL

P₂Ar = 457 torr

Finally we calculate the total pressure, adding the partial pressures:

• Total pressure = P₂He + P₂Ar = 733 torr