Study Guides/Chemistry/Weak Acid and Weak Base
Study Guide · Chemistry

Weak Acid and Weak Base: Definition and Examples

In Class 10 and 11 Chemistry, acids and bases are classified as strong or weak based on how completely they dissociate in water. This is different from concentrated vs dilute.

Question (Click to Flip)

What is a weak acid? Give two examples.

Answer

A weak acid is one that only partially dissociates in water, producing few H⁺ ions. Examples: Acetic acid (CH₃COOH) found in vinegar, and Carbonic acid (H₂CO₃) found in fizzy drinks.

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Key Facts

Weak Acid: Partially ionizes — CH₃COOH (vinegar), H₂CO₃.

Weak Base: Partially ionizes — NH₄OH (ammonia), Mg(OH)₂.

Strong ≠ Concentrated: Strength = degree of ionization. Concentration = amount dissolved.

Weak Acids

A Weak Acid is one that does NOT completely dissociate (ionize) into ions when dissolved in water. Only a small fraction of its molecules break apart.

Examples of Weak Acids:

  • CH₃COOH (Acetic acid / Vinegar)
  • H₂CO₃ (Carbonic acid — in fizzy drinks)
  • HF (Hydrofluoric acid)
  • H₃PO₄ (Phosphoric acid)

Strong Acids (for comparison): HCl, H₂SO₄, HNO₃ — completely dissociate in water.

Weak Bases

A Weak Base is one that does NOT completely dissociate in water — only a small fraction produces OH⁻ ions.

Examples of Weak Bases:

  • NH₄OH (Ammonium hydroxide / Ammonia solution)
  • Mg(OH)₂ (Magnesium hydroxide — in antacids)
  • Ca(OH)₂ (Calcium hydroxide — slaked lime; moderately weak)

Strong Bases (for comparison): NaOH, KOH — completely dissociate in water.

Strong vs Weak: Quick Comparison

PropertyStrong Acid/BaseWeak Acid/Base
DissociationComplete (100%)Partial (small %)
pH of acidVery low (0-2)Moderate (3-6)
ConductivityHighLow
ExampleHCl, NaOHCH₃COOH, NH₄OH

Questions and Answers

What is a weak acid? Give two examples.+

A weak acid is one that only partially dissociates in water, producing few H⁺ ions. Examples: Acetic acid (CH₃COOH) found in vinegar, and Carbonic acid (H₂CO₃) found in fizzy drinks.

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