Understanding Acids

📚 Key Concepts

🔹 Real-Life Example

When you bite into a lemon, your face pickles up due to its sour taste. This sourness comes from citric acid present in the lemon. Similarly, when milk goes bad, it tastes sour because lactic acid forms. The burning sensation you feel when ant bites is due to formic acid. All these substances that taste sour and can corrode metals are acids!

Acid: Acids are substances that furnish hydrogen ions (H⁺) or hydronium ions (H₃O⁺) when dissolved in water. They have a sour taste and can turn blue litmus paper red.

🧪 Important Concepts

🔸 Key Characteristics of Acids

• Sour taste (like lemon, vinegar)
• Turn blue litmus paper red
• Conduct electricity in aqueous solution
• React with metals to produce hydrogen gas
• React with bases to form salt and water
• Release H⁺ ions in water

🔸 Classification of Acids

Based on Source:

• Organic Acids: Found in living organisms (citric acid, acetic acid, lactic acid)
• Inorganic/Mineral Acids: From rocks and minerals (HCl, H₂SO₄, HNO₃)

Based on Strength:

• Strong Acids: Completely ionize in water (HCl, H₂SO₄, HNO₃)
• Weak Acids: Partially ionize in water (CH₃COOH, citric acid)

Based on Basicity:

• Monobasic: Release one H⁺ ion (HCl, HNO₃)
• Dibasic: Release two H⁺ ions (H₂SO₄, H₂CO₃)
• Tribasic: Release three H⁺ ions (H₃PO₄)

🔍 Advanced: Acid Behaviour

Acids show their acidic properties only in the presence of water. Dry HCl gas doesn’t turn blue litmus red, but HCl in water (hydrochloric acid) does. This is because acids release H⁺ ions only in aqueous solutions.