Question

Chlorophyll contains $2.68\%$ of magnesium by mass. Calculate the no. of $Mg$ atom in $2g$ of chlorophyll.

• A. $2.5\times {10}^{21}$
• B. $1.35\times {10}^{21}$
• C. $4.8\times {10}^{20}$
• D. $6.1\times {10}^{21}$

Answer 1

Answer: (B)

$1.35\times {10}^{21}$

mass of chlorophyll $=2g$

mass of magnesium in chlorophyll $=2g\times 2.68\%$

$=\frac{2\times 2.68}{100}=5.36\times {10}^{-2}$

No.of mole of magnesium $\frac{5.36\times {10}^{-2}}{29}$

No. of atom of magnesium $=6.023\times {10}^{23}\times \frac{3.36\times {10}^{-2}}{24}$

$=1.35\times {10}^{21}atom$

Option $B$