Question

How many moles are equivalent to 71.1 grams of barium nitride?

Answer 1

`"71.1 g Ba"_3"N"_2"` is equivalent to `"0.162 mol Ba"_3"N"_2"`.

Explanation:

First you need to know the molar mass of barium nitride, `("Ba"_3"N"_2")`, which is `"439.995 g/mol"`.
https://pubchem.ncbi.nlm.nih.gov/compound/15251597

Divide the given mass of barium nitride, by its molar mass. Since molar mass is a fraction, g/mol, I prefer to divide by multiplying by its reciprocal, mol/g.

`71.1color(red)cancel(color(black)("g Ba"_3"N"_2))xx(1"mol Ba"_3"N"_2)/(439.995color(red)cancel(color(black)("g Ba"_3"N"_2)))="0.162 mol Ba"_3"N"_2"`