What characterizes a chemical buffer solution consisting of ethanoic acid and sodium ethanoate?
Answer and explanation
Correct answer: A. It resists changes in pH when small amounts of acid or base are added
- Step 1: A buffer solution contains a weak acid and its conjugate base in comparable concentrations.
- Step 2: When H+ is added, ethanoate ions consume it: CH3COO- + H+ -> CH3COOH.
- Step 3: When OH- is added, ethanoic acid neutralizes it: CH3COOH + OH- -> CH3COO- + H2O.
- Step 4: This maintains nearly constant pH within the buffer capacity.
Answer
It resists changes in pH when small amounts of acid or base are added.
Why not the others: 'It maintains a neutral pH of exactly 7.00 under all conditions' is incorrect because an acetic acid buffer has an acidic pH around 4.76; 'It neutralizes unlimited quantities of concentrated strong base' ignores buffer capacity limits; 'It prevents precipitation of all insoluble salts' confuses buffers with complexing agents.
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