3 g of carbon combines with 8 g of oxygen to give 11 g of carbon dioxide.
We know that carbona nd oxygen react in ratio of 3:8 to give carbon dioxide gas. Hence, even if 3 g of carbon is burnt in 50 g of oxygen, only 8 g of oxygen will participate in the reaction to give 11 g of carbon dioxide gas. The remaining 42 g of oxygen will be left un-reactive.
The above answer is governed by the law of constant proportions.