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#?

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Answer 1 · 2016-02-22T01:43:51

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

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

#P_"Total"=P_"He"+P_"CO2"+P_"O2"#

Rearrange the equation to isolate #P_"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_"O2"=18.5"kPa"#

Answer 2 · 2016-02-22T01:45:29

The total pressure of #101.4# #kPa# is made up of the sum of the partial pressures of the three gases, so #P_(O2)=101.4-82.5-0.4=18.5# #kPa#.

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

#P_("tot")=P_(O2)+P_(He)+P_(CO2)#

We want to know the partial pressure of oxygen, #P_(O2)#, so we rearrange:

#P_(O2)=P_("tot")-P_(He)-P_(CO2)#

Substituting in the known values gives the answer shown above.