A solution of approximately 0.1 M benzoic acid, C₇H₆O₂, is titrated against a 0.1004 M solution of sodium hydroxide, NaOH - VCE - SSCE Chemistry - Question 6 - 2016 - Paper 1
Question 6
A solution of approximately 0.1 M benzoic acid, C₇H₆O₂, is titrated against a 0.1004 M solution of sodium hydroxide, NaOH.
Which one of the following pH curves repr... show full transcript
Worked Solution & Example Answer:A solution of approximately 0.1 M benzoic acid, C₇H₆O₂, is titrated against a 0.1004 M solution of sodium hydroxide, NaOH - VCE - SSCE Chemistry - Question 6 - 2016 - Paper 1
Step 1
Identify the Reaction
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Answer
In this titration, benzoic acid (a weak acid) reacts with sodium hydroxide (a strong base). The reaction can be represented as:
The benzoate ion (C₇H₅O₂⁻) is formed as the conjugate base.
Step 2
Expected pH Change
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Answer
Initially, the pH of the benzoic acid solution is low due to the presence of hydrogen ions. As NaOH is added, the pH will gradually increase. At the equivalence point, where the amount of acid equals the amount of base, the solution will exhibit a sharp rise in pH.
Step 3
Determine the Equivalence Point
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Answer
The equivalence point for the titration of a weak acid with a strong base is typically above pH 7. This is because the resulting solution will contain the conjugate base, which slightly increases the pH.
Step 4
Select the Correct pH Curve
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Answer
Based on the titration behavior observed, the correct pH curve that represents this titration would be option D. This curve shows a low initial pH, a steep rise at the equivalence point, and a plateau at a pH greater than 7, consistent with the behavior of a weak acid being titrated by a strong base.
