Explain the concept of a redox reaction and its... - SS1 Chemistry Redox Reactions Question

A redox reaction, also known as an oxidation-reduction reaction, involves the transfer of electrons between species. In these reactions, one species undergoes oxidation (loses electrons) while another species undergoes reduction (gains electrons). This transfer of electrons allows the species involved to achieve a more stable state. Redox reactions are essential in various chemical processes, including energy production, corrosion, and biological reactions.

 

Let's consider the example of the reaction between magnesium (Mg) and hydrochloric acid (HCl):

 

Mg + HCl → MgCl₂ + H₂

 

Step 1: Identify the oxidation states of each element in the reaction.

In this case, Mg is in its elemental form, so its oxidation state is 0. H is typically +1, and Cl is typically -1.

 

Step 2: Determine which species are being oxidised and reduced.

In this reaction, Mg is being oxidised from 0 to +2, while H is being reduced from +1 to 0.

 

Step 3: Balance the atoms other than hydrogen and oxygen.

In this case, we have one magnesium (Mg) atom on the left side and one on the right side, so they are already balanced. The same applies to the chlorine (Cl) atoms.

 

Step 4: Balance oxygen atoms by adding water (H₂O) molecules.

Since there are no oxygen atoms on the left side, we need to add water on the right side. Let's add one water molecule to balance the oxygen atoms:

 

Mg + HCl → MgCl₂ + H₂O

Step 5: Balance hydrogen atoms by adding hydrogen ions (H⁺).

To balance the hydrogen atoms, we need to add two hydrogen ions on the left side:

 

Mg + 2HCl → MgCl₂ + H₂O

 

Step 6: Balance the charges by adding electrons (e⁻).

Since magnesium (Mg) loses two electrons during oxidation, we need to add two electrons on the right side:

 

Mg + 2HCl → MgCl₂ + H₂O + 2e⁻

 

Step 7: Verify that the charges and the number of atoms are balanced.

The equation is now balanced in terms of atoms and charge:

 

Mg + 2HCl → MgCl₂ + H₂O + 2e⁻

 

This balanced equation represents the redox reaction between magnesium and hydrochloric acid.