How do you Balance the Equation Al(s) + HCl(l) → AlCl3 (s) + H2(g)?

By BYJU'S Exam Prep

Updated on: September 25th, 2023

The balanced chemical reaction of Al(s) + HCl(l) → AlCl₃ (s) + H₂(g) is Al(s) + 3HCl(l) → AlCl₃ (s) + H₂(g).

Step 1: Firstly note the given unbalanced reaction

Al(s) + HCl(l) → AlCl₃ (s) + H₂(g)

Aluminium Hydrochloric acid Aluminium chloride Hydrogen

Step 2: Calculation of each atom’s oxygen status

List each atom’s oxidation numbers.

Aluminum is in metallic form on the reactant side, or RHS, and the oxidation state is zero. When aluminium trichloride is formed, each chlorine receives one electron from aluminium, causing the oxidation state to shift to +3.

Since it gives an electron to the chlorine atom, the hydrogen atom in hydrochloric acid is in the +1 oxidation state. It liberates hydrogen gas, with no oxidation state, on the product side.

Chlorine has an oxidation state of -1 on both sides because it is highly electronegative than aluminium and hydrogen. As a result, it can accept an electron from either one.

On RHS, Al = 0, H = +1, Cl = -1

On LHS, Al = +3, H = 0, Cl = -1

Table of content

1. How do you Balance the Equation Al(s) + HCl(l) → AlCl3 (s) + H2(g)?

Step 3: Divide the reactions of reduction and oxidation.

Write the couplets for reduction and oxidation.

Reduction: Since hydrogen’s oxidation state moves from +1 in hydrochloric acid to 0 in hydrogen gas, the reaction is a half-reaction in reduction.

HCl → H₂

A half-reaction of oxidation occurs when the oxidation state of aluminium moves from 0 in the metal state to +3 in the trichloride form of aluminium.

Al → AlCl₃

Step 4: Balancing all atoms except Hydrogen and Oxygen.

All elements, save Hydrogen and Oxygen, should be in balance. Multiplying HCl by 3 will balance the chlorine atoms on either side.

The reaction is,

Al(s) + 3HCl(l) → AlCl₃ (s) + H₂(g)

Aluminium Hydrochloric acid Aluminium chloride Hydrogen

Step 5: Balancing of Oxygen and Hydrogen.

Balance the Hydrogen atoms.

To balance the Hydrogen atom multiply Al and AlCl₃ by 2, H2 by 3, and HCl by 2

Hence, Al(s) + 3HCl(l) → AlCl₃ (s) + H₂(g) is the balanced reaction

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