Answer
$8.47gO_{2}$, law of constant composition.
Work Step by Step
The law of constant composition states that a chemical compound contains a fixed ratio of component elements. Since it contains 1.50g carbon for every 2.00g oxygen, we can create a ratio of oxygen to carbon.
$\frac{2.00gO_{2}}{1.50gC}=1.33333$, there are 1.33333g oxygen for every gram of carbon. To find how many grams of oxygen there will be for 6.35g carbon, we simply multiply by the carbon to oxygen conversion factor and divide by 1 to cancel units.
$6.35gC\times\frac{1.33333gO_{2}}{1gC}=8.47gO_{2}$
