Learning Goal: To use partial pressure in gas law calculations. In a mixture of

Question

Learning Goal:

To use partial pressure in gas law calculations.

In a mixture of gases, the total pressure of the gas mixture is equal to the sum of the partial pressures of the individual gases. For example, if you have a mixture of helium at 2 atm and argon at 4 atm , then the total pressure of the gas inside the cylinder is 6 atm

Part A

A mixture of He, Ar, and Xe has a total pressure of 2.40 atm . The partial pressure of He is 0.200 atm , and the partial pressure of Ar is 0.450 atm . What is the partial pressure of Xe?

Express your answer to three significant figures and include the appropriate units.

Part B

A volume of 18.0 L contains a mixture of 0.250 mole N2 , 0.250 mole O2 , and an unknown quantity of He. The temperature of the mixture is 0 C , and the total pressure is 1.00 atm . How many grams of helium are present in the gas mixture?

Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

Part A)

Partial pressure of Xe = 2.40 - (0.2 + 0.45) = 1.75 atm

Part B) Total moles = PV/RT

= 1 x 18/0.08205 x 273

= 0.8036 mols

moles of He = 0.8036 - (0.250 + 0.250) = 0.3036 mols

grams of He = 0.3036 x 4 = 1.214 g

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