Question

A sample of a compound contains `"0.100 g H"` and `"4.20 g N"`. What is its empirical formula?

Answer 1

The empirical formula is `"HN"_3`.

Explanation:

The simplest formula for a compound is its empirical formula, which represents the lowest whole number ratio of elements in the compound.

We must first determine the number of moles of each element by dividing its mass by its molar mass, which is its atomic weight on the periodic table in g/mol.

`0.100"g H"xx(1"mol H")/(1.00794"g H")="0.0992 mol H"`

`4.20"g N"xx(1"mol N")/(14.007"g N")="0.300 mol N"`

Now we must determine the mole ratios between the elements by dividing the moles of each element by the least number of moles.

`"H":` `(0.0992cancel"mol")/(0.0992cancel"mol")="1.00"`

`"N":` `(0.300cancel"mol")/(0.0992cancel"mol")="3.02~~3`

The empirical formula is `"HN"_3`.