Some Basic Concepts Of Chemistry Question 152

Question: Chlorophyll, the green colouring matter of plants responsible for photosynthesis, contains 2.68% of magnesium by mass. Calculate the number of magnesium atoms in 2.00g of chlorophyll.

Options:

A) $ 1.345\times 10^{21} $

B) $ 1.345\times 10^{20} $

C) $ 13.45\times 10^{21} $

D) $ 1.345\times 10^{23} $

Show Answer

Answer:

Correct Answer: A

Solution:

[a] $ \because $ 100 g chlorophyll contains 2.68 g $ Mg=\frac{2.68}{24} $ mole $ Mg $

$ \therefore $ 2g chlorophyll contains $ \frac{2.68\times 2}{24\times 100} $ mol $ Mg=2.2\times {10^{-3}} $ mole $ Mg $ No. of $ Mg $ atoms $ =2.2\times {10^{-3}}\times 6.023\times 10^{23} $

$ =1.345\times 10^{21} $ atoms of $ Mg $ .



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