Carboxylic acidsIB MYP Chemistry: Subtopic test

1. 1
   A teacher writes the formulae HCOOH, CH₃COOH, C₂H₅COOH and C₃H₇COOH on the board. They are the first four members of a family of organic compounds.

   (a)

   What is the functional group of the carboxylic acids?

   [1 mark]

   • A–COOH
   • B–OH
   • CC=C
   • D–CH₃

   (b)

   What is the name of the compound with the formula CH₃COOH?

   [1 mark]

   • AMethanoic acid
   • BPropanoic acid
   • CEthanol
   • DEthanoic acid

   (c)

   Explain why ethanoic acid is a weak acid, whereas hydrochloric acid of the same concentration is a strong acid.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student investigates how ethanoic acid reacts with different substances: magnesium ribbon, calcium carbonate and sodium hydroxide solution.

   (a)

   Which products are formed when ethanoic acid reacts with calcium carbonate?

   [1 mark]

   • ACalcium ethanoate and hydrogen
   • BCalcium chloride, water and carbon dioxide
   • CCalcium ethanoate, water and carbon dioxide
   • DCalcium ethanoate and water only

   (b)

   Which gas is produced when magnesium reacts with ethanoic acid?

   [1 mark]

   • ACarbon dioxide
   • BHydrogen
   • COxygen
   • DChlorine

   (c)

   Write the word equation for the reaction between ethanoic acid and sodium hydroxide.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student compares ethanoic acid and hydrochloric acid, each with a concentration of 0.10 mol dm⁻³. She measures the pH of each acid with a pH meter. She then times how long a 2 cm strip of magnesium ribbon takes to dissolve completely in 50 cm³ of each acid at 20 °C. Hydrochloric acid had a pH of 1.0 and the magnesium dissolved in 40 s. Ethanoic acid had a pH of 2.9 and the magnesium dissolved in 210 s.

   (a)

   State a testable hypothesis that the student could have been investigating, and include a scientific reason for it.

   [3 marks]

   (b)

   Evaluate the investigation. In your answer, calculate how many seconds longer the magnesium took to dissolve in ethanoic acid, state whether the results support the hypothesis, give one weakness of the method and suggest one improvement.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A company in Italy makes pickled vegetables in jars of vinegar, and also makes fruit-flavoured sweets. For the sweets it uses artificial flavourings: esters made in a factory by heating carboxylic acids with alcohols and a concentrated sulfuric acid catalyst.

   (a)

   Discuss the benefits and drawbacks of using esters made in a factory as fruit flavourings instead of flavourings extracted from fruit.

   [6 marks]

   (b)

   Evaluate the use of vinegar rather than refrigeration to preserve vegetables.

   [6 marks]

   Total for question 4: 12 marks

End of questions