Question

$1 \,g$ of activated charcoal at STP undergoes monolayer of adsorption of $NH _{3}$. If $1 \,g$ of charcoal has surface area of $2 \times 10^{2} \,m ^{2}$ and effective surface area of $NH _{3}$ molecule is $0.17\, nm ^{2}$, the millimoles of $NH _{3}$ adsorbed on $20 \,g$ of charcoal is _____ .
$\left[ N _{ A }=6.0 \times 10^{23} \,mol ^{-1}\right]$

Answer 1

Surface area of charcoal available for adsorption
$=20 \times 2 \times 10^2 m^2 = 4 \times 10^3 m^2$
Effective surface area of $1\,NH_3$ molecule
$=0.17\,nm^2$
$0.17 \times (10^{-9})^2 = 0.17 \times10^{-18} m^2$
Number of molecules of $NH_3$ adsorbed
$= \frac{4 \times 10^3}{0.17 \times 10^{-18}} = 2.35 \times 10^{22}$ molecules
Amount of $NH_3$ adsorbed $= \frac{2.35 \times 10^{22}}{6.0 \times 10^{23}}$
$= 0.03917\, mol$
$39.17\,m\, mol$