Question

In the reaction $ {H_2} + {O_2} \to {H_2}O $ . If $ 6g $ of $ {H_2} $ combines with $ 64g $ of $ {O_2} $ . Find the mass of excess reagent left?
(A) $ 32g $
(B) $ 48g $
(C) $ 16g $
(D) None of these

Answer 1

Hint: Balanced chemical reaction: The reaction in which the number of atoms on both the sides i.e. on the reactant side and on the product side are same, are known as balanced chemical reaction. By balanced chemical reaction we get the relation between the number of moles of reactants with the number of moles of products.

Complete step by step solution
First of all we will talk about reagents and products.
Reagents: those compounds which react with each other to form the other compounds, are known as reagents. They are present on the left side of the reaction.
Products: The compounds formed by the reaction of reagents, are known as products. They are present on the right side of the reaction.
Balanced reaction: The reaction in which the number of all atoms on both sides i.e. on the reactant side and on the product side are same, are known as balanced reactions. By the balanced chemical reaction we get to know the relation between the number of moles of reactants with the number of moles of product.
In the given question the reaction is as:
 $ {H_2} + {O_2} \to {H_2}O $ this is not a balanced reaction. After balancing the reaction we will get
 $ {H_2} + \dfrac{1}{2}{O_2} \to {H_2}O $ i.e. if two grams of hydrogen will react with $ 16g $ of oxygen then $ 18g $ of water molecule will be form.
But if we use $ 6g $ of hydrogen then $ 48g $ of oxygen will require to produce $ 54g $ of water.
But here we are given $ 6g $ of $ {H_2} $ combined with $ 64g $ of $ {O_2} $ so $ 64 - 48 = 16g $ oxygen which is excess reagent (present in large quantity) will remain unreacted.
Hence option C is right.

Note
Number of moles is defined as the ratio of mass of substance to the molar mass of the substance. In the balanced chemical reaction we can get the information about how much moles will react with how much moles of other reactants to form the product of given quantity.