Which set of solute will form a buffer when dissolved in water to make 1 liter of solution?

Correct answer: D. 4 moles of CH3COOH with 4 mole of NaCl

  • A. 1 mole of NH3 with 2 moles of HCl
  • B. 0.0002 mole of HCl
  • C. 2 moles of NaCl with 2 mole of HCl
  • D. 4 moles of CH3COOH with 4 mole of NaCl

Explanation

A buffer solution is typically made from a weak acid and its conjugate base, or a weak base and its conjugate acid. Option D is the correct answer because it includes acetic acid (CH3COOH), a weak acid, and the sodium ion from NaCl. The CH3COO- ion acts as the conjugate base, forming an effective buffer. Options A, B, and C do not have the necessary components to form a buffer system: Option A is an acidic solution, Option B is a dilute acid, and Option C is a combination of a strong acid and a salt, none of which can resist pH changes effectively.

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About Acids, Bases and Salts

Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.

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