Question

In a compound of magnesium(Mg=24) and nitrogen (N=14), 18g of magnesium combines with 7g of nitrogen. Calculate simple ratio of gram-atoms of magnesium to gram-atoms of nitrogen and hence the simplest formula of the compound formed.

Answer 1

18g of Magnesium in mol is equal to 18g / 24 gmol-1 = 0.75 mol

7g of nitrogen in mol is equal to 7g / 14 gmol-1 = 0.5 mol

Thus when 18 g of magnesium reacts with 7g of nitrogen it implies 0.75 mol of magnesium reacts with 0.5 mol of nitrogen.

The simplest formula of the compound formed would be found by:

0.75 mol Mg : 0.5 mol N

= 1.5 mol MG : 1 mol N

= 3 mol MG : 2 mol N

Thus the simplest formula for the compound is Mg3N2