Introduction
When magnesium ribbon is dipped in sulphuric acid, a salt called magnesium sulphate forms. This reaction is a classic example of a metal-acid reaction and is commonly used to demonstrate the reactivity of metals with acids.

Reaction
The reaction between magnesium and sulphuric acid can be represented by the following equation:
Mg + H2SO4 → MgSO4 + H2

Explanation
Magnesium Ribbon
Magnesium is a highly reactive metal that readily reacts with substances like oxygen and acids. It is often used in the form of a ribbon to increase its surface area, allowing for a faster reaction.

Sulphuric Acid
Sulphuric acid (H2SO4) is a strong acid commonly used in laboratories and industries. It is highly corrosive and can cause severe burns if it comes into contact with the skin. Sulphuric acid dissociates in water to produce hydrogen ions (H+) and sulphate ions (SO4^2-).

Reaction Mechanism
When magnesium ribbon is dipped in sulphuric acid, the following reaction occurs:

1. The magnesium atoms on the surface of the ribbon react with the hydrogen ions (H+) from the sulphuric acid. This results in the formation of magnesium ions (Mg^2+) and the release of hydrogen gas (H2).
Mg + 2H+ → Mg^2+ + H2

2. The sulphate ions (SO4^2-) from the sulphuric acid combine with the magnesium ions (Mg^2+) to form magnesium sulphate (MgSO4).
Mg^2+ + SO4^2- → MgSO4

Formation of Magnesium Sulphate
Magnesium sulphate is an ionic compound composed of magnesium cations (Mg^2+) and sulphate anions (SO4^2-). It is a white crystalline solid that is soluble in water. When magnesium ribbon is dipped in sulphuric acid, the reaction between magnesium and sulphate ions forms magnesium sulphate as a salt.

Conclusion
In summary, when magnesium ribbon is dipped in sulphuric acid, the reaction between magnesium and the acid leads to the formation of magnesium sulphate salt. This reaction demonstrates the reactivity of metals with acids and is commonly used in educational settings to teach about chemical reactions.