It was found that in a diving gas mixture for a certain altitude, the total predicted pressure is #"8.38 atm"#. If the partial pressure of oxygen gas must be #"0.21 atm"# underwater, what must the mol fraction be of oxygen gas?

1 Answer
Truong-Son N.
May 18, 2017

This is asking you to use assume #"O"_2# is an ideal gas and use the definition of partial pressure:

#P_(O_2) = chi_(O_2(g))P_(t ot)#

where #chi_(O_2(g))# is the mol fraction of #"O"_2# in the diving gas mixture and #P_(O_2)# is its partial pressure in the diving gas mixture.

Since we want #P_(O_2) = "0.21 atm"#, we have:

#"0.21 atm" = chi_(O_2(g))("8.38 atm")#

#=> color(blue)(chi_(O_2(g)) = 0.025)#

or #2.5%#. This should make sense, since if we want only #"0.21 atm"# of #"O"_2# at a higher pressure, we want less than #21%# of the higher pressure to be #"O"_2#.

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