Question

Balance in acidic medium. Show step by step process.

Iron (solid) reacts with hydrochloric acid (liquid) to form aqueous iron(II) chloride and gaseous

hydrogen.

Answer 1

Solution:

Unbalanced chemical equation (acidic medium):

Fe(s) + HCl(aq) → FeCl₂(aq) + H₂(g)

Step 1: Separate the half-reactions:

Fe(s) → Fe²⁺(aq)

H⁺(aq) → H₂(g)

Step 2: Balance elements:

Fe(s) → Fe²⁺(aq)

2H⁺(aq) → H₂(g)

Step 3: Balance the charge of each equation with electrons.

The iron reaction has no charge on the left side and (2+) on the right side. To balance, add 2 electrons to the right side:

Fe(s) → Fe²⁺(aq) + 2e⁻

For the other reaction, there is 2×(1+) = (2+) charge on the left and no charge on the right. So add 2 electrons to the left side:

2H⁺(aq) + 2e⁻ → H₂(g)

Step 4: Scale the reactions so that they have an equal amount of electrons.

In this case, it is already done.

Step 5: Add the reactions and cancel the electrons:

Fe(s) + 2H⁺(aq) → Fe²⁺(aq) + H₂(g)

Balanced chemical equation:

Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)