An element common to all acids is :

Correct option is A

All acids contain hydrogen as a fundamental element. When dissolved in water, acids release hydrogen ions (H⁺), which give them their acidic properties. For instance, HCl (hydrochloric acid) and H₂SO₄ (sulfuric acid) release H⁺ ions in solution. The concentration of H⁺ ions determines the acidity of the solution.

Acids interact with bases to form salts and water in a neutralization reaction, and the presence of hydrogen is essential for these chemical reactions.

Information Booster:

1. Acids are classified into mineral acids (e.g., HCl, H₂SO₄) and organic acids (e.g., acetic acid).
2. The Arrhenius definition states that acids release H⁺ ions in aqueous solutions.
3. The pH scale measures the acidity of a solution; acids have a pH less than 7.
4. Strong acids like HCl completely dissociate in water, while weak acids partially dissociate.
5. Hydrogen ions are highly reactive and form hydronium ions (H₃O⁺) in water.
6. Acids react with metals to produce hydrogen gas.
7. Common uses of acids include industrial processes (sulfuric acid) and food preservation (citric acid).

Additional Knowledge:

• (a) Hydrogen: Present in all acids and responsible for their reactivity.
• (b) Oxygen: Found in some acids like sulfuric acid (H₂SO₄) but not all.
• (c) Sulphur: Specific to sulfuric acid and related compounds.
• (d) Chlorine: Found in hydrochloric acid but not in other acids.