Consider the reaction between liquid water and aqueous magnesium nitride to form solid magnesium oxide and ammonia gas. If magnesium nitride is present in excess, how many moles of water are needed to form 9.17×1023 ammonia molecules?

2.28 moles of water are needed

Explanation:

We need to determine the reaction, to solve this:

The reactans are H₂O and Mg₃N₂

The products are: MgO and NH₃

Equation: 3H₂O + Mg₃N₂ → 3MgO + 2NH₃

We need to determine how many moles are those ammonia molecules, so we apply the NA (6.02×10²³)

Conversion factor 9.17×10²³ molecules . 1 mol/ NA = 1.52 moles

Ratio is 2:3. 2 moles of ammonia can produced by 3 moles of water

Then, 1.52 moles of ammonia must be produced by (1.52 . 3) / 2 = 2.28 moles of water