Answer : The volume of carbon dioxide produced, 6.0 L
Solution : Given,
Volume of oxygen = 3.0 L
First we have to calculate the moles of oxygen.
At STP, 1 mole of gas contains 22.4 L volume of gas.
As, 22.4 L volume of oxygen obtained from 1 mole of oxygen gas
As, 3.0 L volume of oxygen obtained from
moles of oxygen gas
Now we have to calculate then moles of carbon dioxide.
The balanced chemical reaction will be,

From the reaction we conclude that
1 mole of oxygen react to give 2 moles of carbon dioxide
0.1339 mole of oxygen react to give
moles of carbon dioxide
The moles of carbon dioxide gas = 0.267 moles
Now we have to calculate the volume of carbon dioxide.
As, 1 mole of carbon dioxide contains 22.4 L volume of carbon dioxide gas
So, 0.267 mole of carbon dioxide contains
volume of carbon dioxide gas
The volume of carbon dioxide gas = 5.98 L ≈ 6.0 L
Therefore, the volume of carbon dioxide produced, 6.0 L