3.0 g of carbon combines with 8.0 g of oxygen to give 11.0 of carbon dioxide.
So, by the law of definite proportions,
When 3.00 g of carbon is burnt in 50.00 g of oxygen, only 8.00 g of oxygen will be used to produce 11.00 gram of carbon dioxide. The remaining 42.00 g of oxygen will remain unreacted. Law of constant proportion is Held.