Question

Balance the following reaction: $Na + {H_2}O \to NaOH + {H_2}$
A) $2Na + 2{H_2}O \to 2NaOH + {H_2}$
B) $Na + {H_2}O \to NaOH + 2{H_2}$
C) $2Na + {H_2}O \to NaOH + {H_2}$
D) $Na + \dfrac{1}{2}{H_2}O \to NaOH + {H_2}$

Answer 1

Hint: A balanced chemical reaction is the one in which the number of atoms of all the elements are equal on both sides (that is, the reactant and the product side) of the reaction. To balance the given reaction in question, count the number of atoms of each element on both sides and if they are not equal, make them equal by multiplication with a required number.

Complete step by step answer:
If in a chemical reaction, the total number of atoms of each molecule in the reactant side (left-hand side) is equal to the total number of atoms of each molecule in the product side (right-hand side), then the chemical reaction is said to be balanced.
Balancing the given reaction in steps:
The skeletal equation is: $Na + {H_2}O \to NaOH + {H_2}$
Step 1: The three elements involved in the reaction are Na, O and H .Count the number of times an element is involved on both the left-hand side (LHS) and right-hand side (RHS) of the equation.

Element	Reactant (LHS)	Product (RHS)
Sodium(Na)	1	1
Oxygen(O)	1	1
Hydrogen(H)	2	3

Since hydrogen atoms are not equal on both sides, the given equation is an unbalanced equation.
Step 2: Let’s balance the chemical equation. If we multiply $NaOH$ and ${H_2}O$ by 2, we will get a total of four hydrogen atoms on both sides of the equation. Now, to balance sodium atoms, we also need to multiply Na by 2. Thus, we get the equation as:
$2Na + 2{H_2}O \to 2NaOH + {H_2}$
Now, counting the elements on reactant and product side:

Element	Reactant (LHS)	Product (RHS)
Sodium (Na)	2	2
Oxygen (O)	2	2
Hydrogen (H)	4	4

Hence, we get a balanced chemical reaction: $2Na + 2{H_2}O \to 2NaOH + {H_2}$.
Thus, option A is the correct answer.

Note: A balanced chemical reaction always follows the law of conservation of mass. Law of conservation of mass states that mass is neither created nor destroyed in chemical reactions. If we account for all reactants and products in a chemical reaction, then total mass of reactants will always be equal to the total mass of products at any time in a closed system.