Question

Chlorophyll extracted from the crushed green leaves was dissolved in water to make $2L$ solution of $Mg$ of concentration $48ppm$. The number of atoms of $Mg$ in this solution is $x\times 10^{20}$ atoms. The value of $x$ is__________ (Nearest Integer)
(Given : Atomic mass of $Mg$ is $24gmo{l}^{-1}$, $N_A=6.02\times 10^{23}mo{l}^{-1})$

Answer 1

Answer: 24

$ppm=\frac{W_{Mg}}{V_{\text{soln }}}\times 10^6=48$
$\Rightarrow W_{Mg}=\frac{48\times 2\times 1000}{10^6}$
$=48\times 2\times 10^{-3}g$
$n_{Mg}=\frac{W_{Mg}}{24}=\frac{48\times 2\times 10^{-3}}{24}$
$=4\times 10^{-3}$
Number of $Mg$ atoms $=4\times 10^{-3}\times 6.02\times 10^{23}$
$=4\times 6.02\times 10^{20}$
$=24.08\times 10^{20}$
$\therefore x=24.08$