Question

$1.30\, cm ^{3}$ of $N _{2}$ gas at STP is adsorbed per gram of silica gel. The area occupied by nitrogen molecule is $0.16 \,nm ^{2}$. What is the surface area per gram of silica gel? $\left(N_{ A }=6.023 \times 10^{23}\right)$

• A. $1.6 \,m ^{2} / g$
• B. $5.568 \, m ^{2} / g$
• C. $3.48 \, m ^{2} / g$
• D. $4.42 \, m ^{2} / g$

Answer 1

Answer: (B)

Number of $N _{2}$ molecules adsorbed per gram of silica gel
$=\frac{1.30 \times 6 \times 10^{23}}{22400}=3.48 \times 10^{19}$
Area of cross section of molecule $=0.16\, nm ^{2}=1.6 \times 10^{-19}\, m ^{2}$
Surface area covered per gram of silica gel
$=1.6 \times 10^{-19} \times 3.48 \times 10^{19}=5.568 \,m ^{2}$