Question

Chlorophyll is responsible for photosynthesis, that contains $2.68\%$ of magnesium. Calculate the number of magnesium atoms present in $2.00g$ of chlorophyll.

• A. $1.345\times 10^{23}atomsofMg$
• B. $1.345\times 10^{28}atomsofMg$
• C. $1.345\times 10^{22}atomsofMg$
• D. $1.345\times 10^{21}atomsofMg$

Answer 1

Answer: (D)

$100g$ of chlorophyll contains $2.68gMg=\frac{2.68}{24}moleMg$ .
$2g$ of chlorophyll contains $\frac{2.68\times 2}{24\times 100}moleMg=2.2\times 10^{-3}moleMg.$ $No.ofMgatoms=2.2\times 10^{-3}\times 6.023\times 10^{23}$
$=1.345\times 10^{21}atomsofMg$