Question

The total number of electrons in $4.2g$ of $N^{3-}$ ion is $(N_A$ is the Avogadro's number)

• A. $2.1N_A$
• B. $4.2N_A$
• C. $3N_A$
• D. $3.2N_A$

Answer 1

Answer: (C)

Total number of moles $=\frac{4.2}{14}=0.3mol$
$1mol$ of $N^{3-}$ have electrons $=10\times N_0$
$\therefore$ Number of $e^{-}$ in $0.3mol$
$=0.3\times 10\times N_0=3\times N_0$