Question

What is the percent by mass of oxygen in carbon dioxide (CO2)?

Answer 1

molar mass:
 
O2 = 32 g/mol          CO2 = 44 g/mol

% O2 = ( molar mass O2 / molar mass CO2 ) x 100

% O2 = ( 32 / 44 ) x 100

% O2 = 0,7272 x 100

= 72,72% of O2

hope this helps!

Answer 2

Answer : The percent by mass of oxygen in carbon dioxide is, 72.72%

Solution : Given,

Molar mass of oxygen = 16 g/mole

Molar mass of carbon dioxide = 44 g/mole

As we know that there are 2 atoms of oxygen and 1 atom of carbon present in the carbon dioxide.

So, the molar mass of oxygen, $O_2$ = 2 × 16 = 32 g/mole

Now we have to calculate the percent by mass of oxygen in carbon dioxide.

$\%\text{ by mass of oxygen}=\frac{\text{Molar mass of oxygen}}{\text{Molar mass of }CO_2}\times 100$

Now put all the given values in this expression, we get

$\%\text{ by mass of oxygen}=\frac{32g/mole}{44g/mole}\times 100=72.72\%$

Therefore, the percent by mass of oxygen in carbon dioxide is, 72.72%