A mixture of helium, nitrogen and oxygen has a total pressure of 756 mmHg. The partial pressure of helium is 122 mmHg, and the partial pressure of nitrogen is 338 mmHg. What is the
partial pressure (in mmHg) of oxygen in the mixture?

The  partial pressure of oxygen in the mixture is 296 mmHg.

Explanation:

The pressure exerted by a particular gas in a mixture is known as its partial pressure. So, Dalton's law states that the total pressure of a gas mixture is equal to the sum of the pressures that each gas would exert if it were alone.

This relationship is due to the assumption that there are no attractive forces between the gases.

So, in this case, the total pressure is:

PT=Phelium + Pnitrogen + Poxygen

You know:

Replacing:

756 mmHg= 122 mmHg + 338 mmHg + Poxygen

Solving:

756 mmHg - 122 mmHg - 338 mmHg = Poxygen

Poxygen= 296 mmHg

The  partial pressure of oxygen in the mixture is 296 mmHg.

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