Photo AI

You are provided with samples of each of the four compounds - AQA - A-Level Chemistry - Question 7 - 2017 - Paper 2

Question icon

Question 7

You-are-provided-with-samples-of-each-of-the-four-compounds-AQA-A-Level Chemistry-Question 7-2017-Paper 2.png

You are provided with samples of each of the four compounds. K: H3C–C(COOH)–C(Br)–C(OH)–H L: H3C–C(COOH)–C(CH3)–C(OH)–H M: H3C–C(COOH)–C(COOH)–C(OH)–H N: H3C... show full transcript

Worked Solution & Example Answer:You are provided with samples of each of the four compounds - AQA - A-Level Chemistry - Question 7 - 2017 - Paper 2

Step 1

Test with NaHCO₃ / pH Indicator

96%

114 rated

Answer

Perform a test with sodium bicarbonate (NaHCO₃) and a pH indicator.

  • Compounds K and M will react and produce effervescence due to the release of carbon dioxide ( CO₂) from the carboxylic acid group (–COOH). This reaction indicates the presence of the carboxylic acid functional group.
  • Observe pH changes where K and M may turn the indicator color.
  • L and N will show no reaction.

Step 2

Test with Fehling's / Tollens'

99%

104 rated

Answer

Conduct tests with Fehling's solution or Tollens' reagent.

  • Compound N, containing aldehyde groups, will react positively showing a color change (red precipitate in Fehling's).
  • K, L and M which have ketone or alcohol groups may show a weak or no reaction.
  • The distinct positive reaction indicates the presence of the aldehyde functional group in N.

Step 3

Test with Acids (H₂SO₄)

96%

101 rated

Answer

Finally, treat the samples with sulfuric acid (H₂SO₄).

  • Observations may vary: K and M could show ester formation while L containing a branched structure, may not form visible products.
  • N will show no ester formation, confirming the alcohol functionality.

Join the A-Level students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;