Question

`Na_3N` decomposes to form sodium and nitrogen gas at STP. If 13.7 L of nitrogen is produced, how many moles of `Na_3N` was used (22.4 L = 1 mole of any gas) ?

Answer 1

`1.22` mol `Na_3N`

Explanation:

Given: `Na_3N` decomposes to form sodium (Na) and Nitrogen (`N_2)` at STP (standard temperature and pressure). At STP `22.4 L = 1` mole of gas

First you need to write a skeleton equation and then balance it. You need to realize that nitrogen is a diatomic element `N_2`.

skeleton equation: `" "Na_3N -> Na + N_2`

balanced: `" "2Na_3N -> 6Na + N_2`

The balanced equation gives us the mole ratio of sodium nitrate to nitrogen produced: `2/1`.

`13.7 cancel(L N_2) xx (1 cancel(mol N_2))/(22.4 cancel(L N_2)) xx (2 mol Na_3N)/(1 cancel(mol N_2)) = 1.22" mol "Na_3N`