Question

In a compound of magnesium (Mg = 24) and nitrogen (N= 14 ), 18 g of magnesium combines with 7 g of nitrogen.
Deduce the simplest formula by answering the following questions:
(a) how many gram atoms of magnesium are equal to 18 g?
(b) how many grams atoms of nitrogen equal to 7 g of nitrogen?
(c) calculate simple ratio of gram atoms of magnesium to gram atoms of nitrogen and hence the simplest formula of the compound formed.

Answer 1

a,b) Number of moles of magnesium atom = $\frac{18}{24}=0.75$

Number of moles of nitrogen = $\frac{7}{14}=0.5$

Therefore, the number of grams atoms of magnesium in the compound = 0.75

The number of grams atoms of nitrogen in the compound = 0.5

C) Ratio of moles of magnesium and nitrogen atoms = $\frac{0.75}{0.5}=1.5:1=3:2$

Therefore, the simple whole number ration of atoms of magnesium and nitrogen is 3:2

Since the ratio of magnesium and nitrogen atoms is 3:2, the empirical formula of the compound is $M{g}_3{N}_2.$