Consider the balanced equation for the following reaction:
3CuO(s) + 2NH3(g) → 3H2O(l) + 3Cu(s) + N2(g)
If CuO is present in excess, determine the amount of NH3 needed to produce 2.94 moles of H2O.

The amount of ammonia needed is 33.3 g

Therefore, we can also say 1.96 moles of NH₃

Explanation:

The reaction is: 3CuO(s) + 2NH₃(g) → 3H₂O(l) + 3Cu(s) + N₂(g)

If we see stoichiometry, 3 moles of water can be produced by 2 moles of NH₃. We propose this rule of three:

3 moles of water can be produced by 2 mole of ammonia

Then, 2.94 moles of water, must be produced by (2.94 . 2) /3 =1.96 moles of NH₃

If we convert the moles to mass. 1.96 mol . 17 g /1mol = 33.3 g

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).