Question

12 g of an alkaline earth metal gave 14.8 g of its nitride. Atomic weight of that metal is

(a) 20

(b) 12

(c) 40

(d) 14.8

Answer 1

Correct option is (c) 40

Formula of nitride of alkaline earth metal - M₃N₂

Weight of nitrogen combining with 12 g metal = 14.8 - 12 = 2.8 

 Then, atomic mass of M = \(\frac 13 \times \frac{12 \times 28}{2.8} = 40\)