The salt formed when dilute sulphuric acid reacts with excess of potassium hydroxide is potassium sulfate.
The Reaction Explained
When an acid reacts with a base, a salt and water are typically formed. This is known as a neutralization reaction. Sulphuric acid (H₂SO₄) is a strong acid, and potassium hydroxide (KOH) is a strong base.
Sulphuric acid is a diprotic acid, meaning it can donate two protons (H⁺). The reaction with a base like potassium hydroxide can occur in one or two steps, depending on the molar ratio of the reactants.
- Partial Neutralization: If a limited amount of KOH is used, only one proton from H₂SO₄ reacts. This forms potassium hydrogen sulfate (KHSO₄), also known as potassium bisulfate.
H₂SO₄ + KOH → KHSO₄ + H₂O - Complete Neutralization: If enough or excess KOH is present, both protons from H₂SO₄ react with the base. This leads to the formation of potassium sulfate (K₂SO₄), which is the fully neutralized salt.
H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O
The question specifies that there is an excess of potassium hydroxide. This ensures that the reaction proceeds to the complete neutralization step, where both acidic protons of sulphuric acid are removed, reacting with the hydroxide ions from KOH.
As stated in the reference, "Potassium hydroxide reacts with sulphuric acid to produce potassium sulphate and water." The condition of using excess potassium hydroxide confirms that this complete neutralization product, potassium sulfate, is the salt formed.
Chemical Equation
The balanced chemical equation for the reaction between dilute sulphuric acid and excess potassium hydroxide is:
H₂SO₄(aq) + 2KOH(aq) → K₂SO₄(aq) + 2H₂O(l)
In this reaction:
- Reactants:
- Sulphuric Acid (H₂SO₄)
- Potassium Hydroxide (KOH)
- Products:
- Potassium Sulfate (K₂SO₄) - the salt
- Water (H₂O)
Understanding the Products
The key product, apart from water, is the salt potassium sulfate.
- Potassium Sulfate (K₂SO₄): This is an ionic compound composed of potassium ions (K⁺) and sulfate ions (SO₄²⁻). It is a white, crystalline solid that is soluble in water.
- Water (H₂O): Formed from the combination of hydrogen ions (H⁺) from the acid and hydroxide ions (OH⁻) from the base.
Summary Table
| Reactant 1 | Reactant 2 | Condition | Salt Formed | Other Product |
|---|---|---|---|---|
| Dilute Sulphuric Acid | Excess Potassium Hydroxide | Complete Neutralization | Potassium Sulfate | Water |
Using excess potassium hydroxide guarantees that the reaction goes to completion, forming the potassium sulfate salt rather than the intermediate potassium hydrogen sulfate.
