Answer:
72.7%
Step-by-step explanation:
The first thing you need to do here is to figure out the mass of oxygen in
1 mole of carbon dioxide. To do that, you must use the compound's molar mass.
Now, carbon dioxide has a molar mass of 44.01 g mol−1. This means that 1 mole of carbon dioxide has a mass of 44.01 g. Oxygen has a molar mass of 16.0 g mol−1, so 1 mole of oxygen atoms has a mass of 16.0 g.
This means that if you take 44.01 g of carbon dioxide, you know for a fact that it will contain: 32g oxygen.
This means that 100 g of carbon dioxide will contain:
100gCO2 × 32gO2 / 44.01gCO2 = 72.7 g Oxygen
Therefore, carbon dioxide has a percent composition of 72.7% oxygen, i.e. for every 100 gof carbon dioxide you get 72.7 g of oxygen.