Question

Find the number of atoms in 62 g of phosphorous if its gram atomic mass is 31 g.

• A. $2.00\times {10}^{23}$
• B. $3.01\times {10}^{23}$
• C. $1.204\times {10}^{24}$
• D. $1.50\times {10}^{21}$

Answer 1

The correct option is C $1.204\times {10}^{24}$

Given, mass of phosphorus = 62 g
The gram atomic mass (GAM) of phosphorus = 31 g
Also, 1 mole = $6.023\times {10}^{23}$ particles
$\therefore$ Number of moles of phosphorus
= $\frac{\text{Given mass in grams}}{\text{G.A.M}}$ ... (i)

Substituting the value of given mass in grams and GAM in equation (i) we have:

Number of moles = $\frac{62}{31}$ = 2 moles
$\therefore$ The number of atoms present in 62 grams of phosphorous = $2\times N_A$
= $2\times 6.23\times {10}^{23}$
= $12.04\times {10}^{23}$ atoms.