A compound of hydrogen and oxygen is analyzed and a sample of the compound yields 0.590 g of hydrogen and 9.40 g of oxygen. The molecular mass of this compound is 34.00 g/mol. Find the empirical formula and the molecular formula for the compound?

1 Answer
anor277
Nov 22, 2017

Well, it looks likely that we got #"hydrogen peroxide"#, #H_2O_2#...

Explanation:

But we must interrogate the #"empirical formula"#, and then use the quoted molecular mass to calculate the #"molecular formula..."#

And thus for the given mass of compound we gots....

#(0.590*g)/(1.00794*g*mol^-1)=0.585*mol# with respect to hydrogen....

and #(9.40*g)/(15.00*g*mol^-1)=0.585*mol# with respect to oxygen....

And thus we get the #"empirical formula,"# the simplest whole number ratio representing constituent atoms in a species of ...

#H_((0.585*mol)/(0.585*mol))O_((0.585*mol)/(0.585*mol))=HO#...

But it is a fact that the #"molecular formula"# is a simple whole number multiple of the #"empirical formula."#.

And thus in terms of the given #"molecular mass...."#

#34.00*g*mol^-1=nxx{1.00794+15.999}*g*mol^-1#...where of course #1.00794*g*mol^-1# and #15.999*g*mol^-1# are the respective ATOMIC masses of hydrogen and oxygen....

And so #n=(34.00*g*mol^-1)/({1.00794+15.999}*g*mol^-1)#

Clealry, #n=2#, and the #"molecular formula"-=H_2O_2#, #"hydrogen peroxide"# as we anticipated.....

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