For this case we have the
![CO_ {2}](https://img.qammunity.org/2020/formulas/chemistry/middle-school/wzmx5ms9gdgn2vfr3ors8dhwiuhspnv333.png)
It is composed of one atom of carbon and two of oxygen.
The atomic mass of carbon and oxygen, which can be found in a periodic table, are given by:
![C: 12 \frac {g} {mol}\\O: 16 \frac {g} {mol}](https://img.qammunity.org/2020/formulas/chemistry/middle-school/ysq8v5zle8prnb92nzkbuxypwss5xznmqz.png)
Then, we find the atomic mass of
:
![1 * 12 \frac {g} {mol} = 12 \frac {g} {mol}\\2 * 16 \frac {g} {mol} = 32 \frac {g} {mol}](https://img.qammunity.org/2020/formulas/chemistry/middle-school/5li3dda2yagvezfjyt974ogyxw4wv8nrhb.png)
Adding we have:
![44 \frac {g} {mol}](https://img.qammunity.org/2020/formulas/chemistry/middle-school/1sjbmc4wat9kf1knpzhhbm0fcaa313eot7.png)
To find the percentage of oxygen, we divide the atomic mass of the two oxygen atoms between that of
![CO_(2):](https://img.qammunity.org/2020/formulas/chemistry/middle-school/9imjkrc0xazm0bybukr9a4rf5xscm4aznb.png)
%
Thus, the percentage of oxygen is 72.73%
Answer:
72.73%