Question

How many grams of magnesium oxide is formed when $4.8gm$ of magnesium is combined with $3.2gm$ of oxygen.
(A) $4.2gm$
(B) $3.2gm$
(C) $8gm$
(D) $16gm$

Answer 1

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:
$2Mg + {O_2} \to 2MgO$ .
Number of moles of magnesium will be $\dfrac{{4.8}}{{24}} = 0.2$ (because molecular mass of magnesium is $24$ and given mass is $4.8$ ) and the number of moles of oxygen will be $\dfrac{{3.2}}{{32}} = 0.1$ (because molecular mass of oxygen is $32$ and given mass is $3.2$ ). So $0.1$ mole of magnesium oxide will be formed during the reaction. Hence $8gm$ of magnesium oxide will form.
Hence, option C is correct.

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.