Acids, Bases and Salts — Important Questions

H⁺ ions

Step 1: All acids release hydrogen ions (H⁺) when dissolved in water. Step 2: These H⁺ ions actually exist as hydronium ions (H₃O⁺) by combining with water molecules. Step 3: The concentration of H⁺ ions determines the strength of acidity - more H⁺ ions mean stronger acid. Step 4: This is why dry HCl gas doesn't show acidic properties until dissolved in water. Step 5: OH⁻ ions are responsible for basic nature, while Cl⁻ and Na⁺ are just spectator ions.

Neutralization

Step 1: Neutralization is the reaction between an acid and base that produces salt and water. Step 2: The general reaction is: Acid + Base → Salt + Water. Step 3: During this process, H⁺ ions from acid combine with OH⁻ ions from base to form water (H₂O). Step 4: The remaining ions form the salt, making the solution neutral (pH = 7). Step 5: For example, HCl + NaOH → NaCl + H₂O demonstrates perfect neutralization.

Magnesium hydroxide

Step 1: Antacids are mild bases used to neutralize excess stomach acid. Step 2: Magnesium hydroxide [Mg(OH)₂], known as 'Milk of Magnesia', is a common antacid. Step 3: It reacts with excess HCl in stomach: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O. Step 4: This neutralization relieves acidity and prevents stomach irritation. Step 5: Hydrochloric acid would worsen acidity, sodium chloride is neutral, and carbon dioxide doesn't neutralize acids.

Sodium hydrogencarbonate

Step 1: Baking soda is chemically known as sodium hydrogencarbonate with formula NaHCO₃. Step 2: It is a mild, non-corrosive basic salt used in cooking and household applications. Step 3: When heated, it decomposes: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂. Step 4: The CO₂ released makes food items like cakes and bread soft and spongy. Step 5: Sodium carbonate is washing soda, sodium chloride is common salt, and sodium hydroxide is caustic soda.