A 2.0 g sample of a plant extract containing chlorophyll is analyzed. It is found to contain exactly 1.5055 10²⁰ atoms of magnesium. The mass percentage of magnesium in the extract is: (Given : Atomic mass of Mg is 24 u , N_A = 6.022 10²³ mol ⁻¹ )

Step-by-step solution

Number of moles of Mg atoms = 1.5055 10²⁰ 6.022 10²³ = 0.25 10⁻³ mol = 2.5 10⁻⁴ mol Mass of Mg in the sample = 2.5 10⁻⁴ mol 24 g mol ⁻¹ = 60 10⁻⁴ g = 0.006 g Mass percentage of Mg = Mass of Mg Total mass of extract 100 Mass percentage = 0.006 g 2.0 g 100 = 0.3 % Answer: 0.3 %