A mixture contains 10.0 g each of the three gases nitrogen, oxygen, and argon. What is the mole fraction of nitrogen in the mixture?

2 Answers
Meave60 · Media Owl
Mar 28, 2015

The mole fraction of nitrogen gas in the mixture is 0.338.

Step 1.
Determine the molar mass of each gas. The molar mass is the atomic mass from the periodic table times the number of subscripts in the formula.

Step 2.
Calculate the number of moles of each gas by dividing the given mass by the molar mass.

Step 3.
Add the moles of the three gases to get the total number of moles in the mixture of gases.

Step 4.
Then divide the number of moles of #"N"_2# by the total number of moles for all three gases combined.

Molar mass of #"N"_2# = #"(2 x 14.0067g/mol) ="28.0134 "g/mol"#
Molar mass of #"O"_2# = #"(2 x 15.999 g/mol) ="31.998 "g/mol"#
Molar mass of #"Ar"# = #"(1 x 39.9948 g/mol) ="39.948 "g/mol"#

#"n"_("N"_2)# = #"10.0 g N"_2/"28.0134 g/mol N"_2"# = #"0.35697 mol N"_2"#

#"n"_("O"_2)# = #"10.0 g O"_2/"31.998 g/mol O"_2"# = #"0.31252 mol O"_2"#

#"n"_("Ar")# = #"10.0 g Ar"/"39.948 g/mol Ar"# = #"0.25033 mol Ar"#

#"n"_("total")# = #"0.35697 mol N"_2 + "0.31252 mol O"_2 + "0.25033 mol Ar"# = #"0.91982 mol"#

Mole fraction of #"N"_2# = #"0.35697 mol"/"0.91982 mol"# = #0.338#

Andrea B.
Mar 28, 2015

the molar fraction is the rate among the number of moles of a determined compound and the number of mole of all the compounds ( Na/Na+ Rb+ Nc). To find the number of mole you must divide the weight of each substance for its molecular mass. Pay attention that for nitrogen and oxigen the molecular mass is the double of their atomic masses (es. for oxigen (10g)/ (32 g/mol). Courage, now works you

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