What is the percent by mass of oxygen in carbon dioxide (co2)?
use

%element=total mass of element in compound/molar mass of compound -x100

27.29%
57.12%
72.71%
79.99%

= 72.73%

Explanation:

The percentage by mass of an element is given by;

% element = total mass of element in compounds/molar mass of compound × 100

The mass of oxygen in carbon dioxide = 32 g

Molar mass of CO2 = 44 g

Therefore;

% of O2 = 32/44 × 100%

             = 72.73%

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