Question

Chlorophyll the green colouring matter of plant contains 2.68% of magnesium. Calculate the number of atoms of $Mg$ in 2g of Chlorophyll.

• A. $6.02\times {10}^{22}$ atoms
• B. $1.34\times {10}^{23}$ atoms
• C. $1.34\times {10}^{24}$ atoms
• D. $1.34\times {10}^{25}$ atoms
• E. None of the above

Answer 1

The correct option is B $1.34\times {10}^{23}$ atoms

since  chlorophyll contains 2.68% Mg therefore weight of Mg in 2g chlorophyll = 2×2.68/100 = .0536 g 
now Mole of Mg = weight/atomic weight
                    = .0536/24
       since 1 mole contains  6.023×10^23 particles
        therefore number of atoms present in .0536/24 mole will be = (.0536/24) × 6.023×10^23
                                                                                               =1.34 × 10^23 atoms of Mg