The sodium salt of propanoic acid (sodium propanoate) is used as a preservative in bread and other baked goods. It can be produced by reacting propanoic acid with sodium hydroxide. In a particular experiment 100 mL of 0.080 M NaOH was added to 100 mL of 0.16 M propanoic acid. Which of the following statements is/are correct? I The pH of the resulting solution will be less than that of the propanoic acid solution. II The resulting solution contains equal amounts of propanoic acid and its conjugate base. III Before the NaOH was added there were no propanoate ions present.

SSCE VCE Chemistry Acid-Base Reactions: The sodium salt of propanoic aci

The sodium salt of propanoic acid (sodium propanoate) is used as a preservative in bread and other baked goods - VCE - SSCE Chemistry - Question 12 - 2008 - Paper 1

Question 12

The sodium salt of propanoic acid (sodium propanoate) is used as a preservative in bread and other baked goods. It can be produced by reacting propanoic acid with so... show full transcript

Worked Solution & Example Answer:The sodium salt of propanoic acid (sodium propanoate) is used as a preservative in bread and other baked goods - VCE - SSCE Chemistry - Question 12 - 2008 - Paper 1

Step 1

I The pH of the resulting solution will be less than that of the propanoic acid solution.

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Answer

This statement is incorrect. The addition of NaOH, a strong base, will increase the pH of the solution. Initially, the solution will become more basic than the propanoic acid solution.

Step 2

II The resulting solution contains equal amounts of propanoic acid and its conjugate base.

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Answer

This statement is correct. In the given reaction, NaOH reacts with the propanoic acid to form sodium propanoate (the conjugate base) and water. Given the stoichiometry of the reactants, at the equivalence point, equal amounts will be present.

Step 3

III Before the NaOH was added there were no propanoate ions present.

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Answer

This statement is correct. Before the addition of NaOH, the system only contains propanoic acid and no sodium propanoate (propanoate ions). Therefore, before NaOH is added, there are indeed no propanoate ions present.

The sodium salt of propanoic acid (sodium propanoate) is used as a preservative in bread and other baked goods - VCE - SSCE Chemistry - Question 12 - 2008 - Paper 1

Worked Solution & Example Answer:The sodium salt of propanoic acid (sodium propanoate) is used as a preservative in bread and other baked goods - VCE - SSCE Chemistry - Question 12 - 2008 - Paper 1

I The pH of the resulting solution will be less than that of the propanoic acid solution.

II The resulting solution contains equal amounts of propanoic acid and its conjugate base.

III Before the NaOH was added there were no propanoate ions present.

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