Analysis of a compound shows that it contains 7.0 g nitrogen and 16.0 g oxygen. What is its empirical formula?

1 Answer
anor277
Oct 23, 2016

#NO_2#

Explanation:

The empirical formula is the simplest whole number that defines constituent atoms in a species.

Using the given masses, and the atomic masses of each constituent, we define an empirical formula this way:

#"Moles of nitrogen"# #=# #(7.0*g)/(7.0*g+16*g)xx1/(14.01*g*mol^-1)=0.0217*mol#.

#"Moles of oxygen"# #=# #(16.0*g)/(7.0*g+16*g)xx1/(15.999*g*mol^-1)=0.0435*mol#.

And thus we have the molar quantities of nitrogen, and oxygen respectively. To access the empirical formula, we simply divide thru by the LOWEST molar quantity, that of nitrogen:

#N:(0.0217*mol)/(0.0217*mol)=1#

#O:(0.0435*mol)/(0.0217*mol)=2#

And thus the empirical formula is #NO_2#.

Note that to find the molecular formula we need an estimate of molecular mass.

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