Question

$12g$ of an alkaline earth metal gives $14.8gm$ of its nitride. Atomic weight of the metal is

• A. 12
• B. 20
• C. 40
• D. 14.8

Answer 1

Answer: (C)

Let the alkaline earth metal be A
$\therefore 3A+N_2\to A_3{N}_2$
$\Rightarrow \frac{Molecularmassofcompd.}{Atomicmassofmetal}=\frac{Wt.ofcompd.}{Wt.ofmetal}$
Let atomic mass of metal be x
$\Rightarrow$ Molecular mass of compound $=3x+28$
$\Rightarrow \frac{3x+28}{3x}=\frac{14.8}{12}\Rightarrow x=40$