Solution: A sample of 1.43 g of helium and an unweighed quantity of O2 are mixed in a flask at room temperature. The partial pressure of helium in the flask is 43.0 torr , and the partial pressure of oxygen is 158 torr .What is the mass of the oxygen in the container?

Problem

A sample of 1.43 g of helium and an unweighed quantity of O2 are mixed in a flask at room temperature. The partial pressure of helium in the flask is 43.0 torr , and the partial pressure of oxygen is 158 torr .

What is the mass of the oxygen in the container?

Solution

We're being asked the mass of oxygen in the container filled with a mixture of oxygen and helium.


Recall that the partial pressure of a gas (PGas) in a mixture is given by:


PGas = χGasPtotal


where χGas = mole fraction of the gas and Ptotal = total pressure of the gas mixture


The mole fraction of the gas is then given by:


χGas = moles Gastotal moles


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