Question

Calculate the mass %of oxygen present in the following compounds (a) water (b) hydrogen peroxide

Answer 1

water H2O

gram molecular weight = 1 x 2 + 16 = 18g

Oxygen = 16 g

% of O = 16/18 x 100% = 800/9 %

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hydrogen peroxide H2O2

total weight = 2x1 + 2x16 = 34 g

oxygen = 2 x 16 = 32 g

% of O = 32/34 x 100% = 1600/17 %

Answer 2

a) molecular mass of O in water = 16g
moleculer mass of H2O = 18 g
mass% of O2 = 16/18×100 =88.8%

b) mass of O2 in peroxide(H2O2) = 32g
mass of peroxide. =34g
mass% of peroxide =32/34×100 =94.1%