Chlorophyll contains 2.68% of magnesium by mass.Calculate the number of magnesium atoms in 3.00 g of chlorophyll

a) 1.98 * 10^{21} atoms b) 6.023 * 10^{23} atoms c) 1.7 * 10^{20} atoms d) 2.8 * 10^{2} ^{2} atoms

We are given that chlorophyll contains 2.68 % of chlorophyll. Therefore mass of magnesium that is present in 3g of chlorophyll is

(2.68 / 100) X 3 = 0.0804g

Thus 3g of chlorophyll contains 0.0804g of Mg. Now the molar mass of magnesium is 24.312g. This means that there are 6.023 X 10^{23} atoms of magnesium present in 24.312g of Mg. So

24.312 g of Mg = 6.023 X 10^{23} atoms of Mg

or 1 g of Mg = (6.023 X 10^{23}/ 24.312) atoms of Mg

Hence 0.0804 g of Mg = (6.023 X 10^{23} X 0.0804)^{ }/ 24.312 atoms of Mg

= 1.992 X 10^{21} atoms of Magnesium.

The option that is closest to the answer is a) 1.98 X 10^{21} atoms

**
**