Question

Calculate the number of moles in
(i) $8g$ of oxygen atoms
(ii) $4.088\times {10}^{21}$ number of oxygen atoms (Atomic mass of $O=16u$)

Answer 1

i) No. of moles in $8g$ of oxygen atom

$n=\frac{m}{M}\times N_A\Rightarrow \frac{8}{16}\times 6.02\times {10}^{23}$

$=3.01\times {10}^{23}$ moles

ii) $6.02\times {10}^{23}$ atoms contains $1$ mole

Then, $4.088\times {10}^{21}$ atom contains $=\frac{4.088\times {10}^{21}}{6.02\times {10}^{23}}=0.67\times {10}^{-2}$ moles.