# A breathing mixture used by deep-sea divers contains helium, oxygen, and carbon dioxide What is the partial pressure of oxygen at 101.4 kPa if P_(He) = 82.5 kPa and P_(CO2) = .4 kPa?

Feb 22, 2016

The partial pressure of oxygen in the mixture is 18.5 kPa.

#### Explanation:

The total pressure is the sum of the partial pressures of the given gases.

${P}_{\text{Total"=P_"He"+P_"CO2"+P_"O2}}$

Rearrange the equation to isolate ${P}_{\text{O2}}$, substitute the given values into the equation and solve.

P_"O2"=P_"Total"-(P_"He"+P_"CO2")

P_"O2"=101.4"kPa"+(82.5"kPa"+0.4"kPa")

${P}_{\text{O2"=18.5"kPa}}$

Feb 22, 2016

The total pressure of $101.4$ $k P a$ is made up of the sum of the partial pressures of the three gases, so ${P}_{O 2} = 101.4 - 82.5 - 0.4 = 18.5$ $k P a$.

#### Explanation:

In a little more detail, the total pressure is the sum of the partial pressures of the gases present:

${P}_{\text{tot}} = {P}_{O 2} + {P}_{H e} + {P}_{C O 2}$

We want to know the partial pressure of oxygen, ${P}_{O 2}$, so we rearrange:

${P}_{O 2} = {P}_{\text{tot}} - {P}_{H e} - {P}_{C O 2}$

Substituting in the known values gives the answer shown above.