Help On Equilibrium Question

[matty.k]

how would i go about this question? should i set up a table?

A mixture of nitrogen and hydrogen was allowed to come to equilibrium at a given temperature.
3H2 + N2 = 2NH3
An analysis of the mixture at equilibrium contained 2.0 mol N2, 3.0 mol H2 and 1.5 mol NH3. How many moles of H2 were present at the beginning of the reaction?

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It's been a long time, but i think that

1.5 mol NH3 means that
0.75 mol of N2 and 2.25 mol of H2 must have reacted.

So the initial mixture must have contained 3.0+2.25 mol = 5.25 mol of H2, or 5.3 to 2 sig figs