Question

E. Tick the most appropriate answer:

2. The equation $\mathrm{Zn}+\mathrm{HCl}\to {\mathrm{ZnCl}}_2+{\mathrm{H}}_2$ , the equation can be balanced by putting.

• A. 2 in front of $\mathrm{Zn}$ on the side reactants.
• B. 2 in front of $\mathrm{HCl}$ on the side reactants.
• C. 2 in front of ${\mathrm{ZnCl}}_2$ on the side products.
• D. 2 in front of ${\mathrm{H}}_2$ on the side products.

Answer 1

The correct option is B

2 in front of $\mathrm{HCl}$ on the side reactants.

An equation in which the number of each atom of an element on the reactants side is equal to the number of each atom of an element on the product side is called a balanced equation

Part 1:

• $\mathrm{Zn}+\mathrm{HCl}\to {\mathrm{ZnCl}}_2+{\mathrm{H}}_2$
• This is an unbalanced equation.
• Because the total number of chlorine atoms on the reactant side is 1, whereas on the product side is 2, and also the total number of hydrogen atoms on the reactant side is 1, whereas on the product side is 2.

Part 2:

• To make them equal, we need to multiply $\mathrm{HCl}$ by with numeral 2 on the reactant side. Therefore, the balanced equation will be:

$\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Zinc}\mathrm{Chloride}}{{\mathrm{ZnCl}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$

• Zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas.
• Hence, Option (B) is the correct answer.