Question

12 g of alkaline earth metal gives 14.8 g of its nitride. Atomic weight of metal is –

• A. 12
• B. 20
• C. 40
• D. 14.8

Answer 1

Answer: (C)

40

Answer 2

(3)

3M + N2$\longrightarrow$ M3N2

Let Atomic wt. of metal = a

so (3a + 28) g nitride contains metal = 3a gram

$\therefore$ 14.8 g nitride contains metal = $\frac{3a}{3a + 28}$ × 14.8 = 12

so a = 40.