Question

Write the balanced chemical equation when zinc reacts with dilute nitric acid.

Answer 1

Hint: Determine the chemical formulas of zinc and nitric acid. The metal reacts with acid and produces salt and hydrogen gas. In the balanced chemical equation, the number of atoms remains the same on both sides of the reaction.

Complete answer:
We have to write a balanced chemical equation when zinc reacts with dilute nitric acid.
When a metal reacts with acids they produced salt and hydrogen gas so we can write the word equation as follows:
Zinc + Nitric acid $\to$ Salt + Hydrogen gas
Now, we have to write the unbalanced chemical equation using chemical formulas of all reactants and products as follows:
Chemical formulas of Zinc and nitric acid are \[{\text{Zn}}\] and \[{\text{HN}}{{\text{O}}_{\text{3}}}\] respectively.
As we know when zinc reacts with dilute nitric acid it produces zinc nitrate salt and hydrogen gas.
The chemical formula of hydrogen gas is \[{{\text{H}}_{\text{2}}}\] and the chemical formula of zinc nitrate is \[{\text{Zn(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}\].
So, the unbalanced chemical equation is:
\[{\text{Zn + HN}}{{\text{O}}_{\text{3}}} \to {\text{Zn(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}} + {{\text{H}}_{\text{2}}} \uparrow \]
Here, we can see that the \[{\text{Zn}}\] is already balanced. To balance the nitrate ion and hydrogen atom we have to add coefficient 2 in front of nitric acid.
So, the balanced chemical equation is:
\[{\text{Zn + 2HN}}{{\text{O}}_{\text{3}}} \to {\text{Zn(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}} + {{\text{H}}_{\text{2}}} \uparrow \]

Note:
In zinc nitrate salt the cation is zinc and anion is nitrate ion. Zinc ion always has +2 charges and nitrate ion always has -1 charge. So two nitrate ions combine with one zinc ion. Hence the chemical formula of zinc nitrate is \[{\text{Zn(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}\]. To balance the reaction we always change the coefficients of chemical species. We cannot change the subscript of chemical species as it will change the chemical identity of the species.