Question

if NA is avogadro's no. then no. of valence electrons in 4.2gm of nitride ions N raised to -3 is
a. 2.4NA b.3.2NA c. 1.6NA d. 3.2 NA
pls give the ans with the soln.

Answer 1

Answer: a. $2.4\times N_A$

Explanation: According to avogadro's law, 1 mole of every substance contains avogadro's number $6.023\times 10^{23}$ of particles.

To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}$

$\text{Number of moles}=\frac{4.2g}{14g/mol}=0.3moles$

$N:7: 2,5$

$N^{3-}:10: 2,8$  valence electrons = 8

Now 1 mole of $N^{3-}$  contains =$8\times 6.023\times 10^{23}=8\times N_A$ of valence electrons

0.3 moles of $N^{3-}$  contains =$\frac{8\times N_A}{1}\times 0.3=2.4\times N_A$ of valence electrons