Question

What is the total number of oxygen atoms in $0.2$ mol of ${Na}_2{B}_4{O}_7.{10H}_{2}O$?

Answer 1

$N{a}_2{B}_4{O}_7.10H_{2}O$.

No. of oxygen atoms/molecule = 17

$\therefore$ Total no. of oxygen atoms

$=17\times 0.2\times 6\times {10}^{23}$

$=2.04\times {10}^{24}$