Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Carboxylic Acids
48 practice questions
Topics covered
Practice questions
11–20 of 20 · Normal
Question 11
3 marks · Normal
Answer and see the solution →Carboxylic acids are classified as weak acids.
(a)[1 mark]Explain what is meant by a 'weak acid'.
(b)[1 mark]Describe what you would observe when sodium carbonate solution is added to ethanoic acid.
(c)[1 mark]State how the reaction of ethanoic acid with sodium carbonate shows its weak acid properties.
Question 12
4 marks · Normal
Answer and see the solution →The table below shows the reaction of four different carboxylic acids with magnesium ribbon. In each case, 10 cm³ of acid at the same concentration is used. The time taken for the reaction to stop is measured:
Carboxylic Acid Time taken for reaction to stop / s methanoic acid 110 ethanoic acid 98 propanoic acid 99 butanoic acid 112 (a)[1 mark]Which acid reacts fastest with magnesium ribbon? Support your answer using data.
(b)[1 mark]Suggest why the reactions do not all take the same time, even though the acids are at the same concentration.
(c)[1 mark]Write the formula for the salt formed when butanoic acid reacts with magnesium.
(d)[1 mark]State one safety precaution when carrying out these reactions.
Question 13
1 mark · Normal
Answer and check →Which statement best describes a weak acid such as ethanoic acid?
- A.It ionises completely in water.
- B.It ionises partially in water.
- C.It does not ionise in water.
- D.It is less dense than water.
Question 14
2 marks · Normal
Answer and see the solution →Give the name and the molecular formula of the carboxylic acid with three carbon atoms.
Question 15
4 marks · Normal
Answer and see the solution →A student adds blue litmus paper to a solution of butanoic acid then tests its pH before and after adding sodium carbonate. Answer the following questions.
(a)[1 mark]State what is observed when the blue litmus paper is placed in butanoic acid.
(b)[1 mark]Give a likely pH value for butanoic acid.
(c)[1 mark]State what you would observe after adding sodium carbonate to the butanoic acid.
(d)[1 mark]Explain why the pH of the solution increases after adding sodium carbonate.
Question 16
3 marks · Normal
Answer and see the solution →A student reacts 4.8 g of magnesium ribbon with excess ethanoic acid. Magnesium reacts with ethanoic acid as shown:
Calculate the maximum volume of hydrogen gas produced at room temperature and pressure (rtp), assuming 1 mole of gas occupies 24 dm³. (Relative atomic mass: Mg = 24)
Question 17
6 marks · Normal
Answer and see the solution →A student is learning about carboxylic acids and how they react with metals.
(a)[1 mark]State the name of the unbranched-chain carboxylic acid with two carbon atoms.
(b)[1 mark]Write the molecular formula for the acid you named in (a).
(c)[2 marks]When this acid reacts with zinc metal, a salt and hydrogen gas are produced.
i. Write a balanced chemical equation (using molecular formulae) for the reaction between the acid from (a) and zinc metal.
(d)[1 mark]Name the salt formed in the reaction in part (c).
(e)[1 mark]Give one observation you would expect when this reaction takes place.
Question 18
6 marks · Normal
Answer and see the solution →A bottle of vinegar is labelled as containing ethanoic acid.
(a)[1 mark]State the name of the main acid found in vinegar.
(b)[2 marks]Explain what is meant by the term 'weak acid', using ethanoic acid as an example.
(c)[2 marks]Vinegar reacts with magnesium metal. Describe the reaction and give one reason why the reaction is slower compared to dilute hydrochloric acid.
(d)[1 mark]State one observation you would make when magnesium reacts with vinegar.
Question 19
6 marks · Normal
Answer and see the solution →A student wants to prepare a sample of sodium butanoate by reacting sodium metal with butanoic acid.
(a)[2 marks]Draw the displayed formula for butanoic acid.
(b)[2 marks]Write a balanced symbol equation (using molecular formulae) for the reaction between sodium metal and butanoic acid.
(c)[2 marks]Calculate the mass of sodium metal required to react completely with 0.10 mol of butanoic acid. (Relative atomic mass: Na = 23)
Question 20
6 marks · Normal
Answer and see the solution →Study the information about the carboxylic acid family and their behaviour as acids.
(a)[2 marks]Give the name and molecular formula of the unbranched-chain carboxylic acid with three carbon atoms.
(b)[2 marks]Explain why carboxylic acids, such as the one named in (a), are described as weak acids.
(c)[2 marks]A student adds magnesium strip to a solution of this acid. The reaction is much slower than when magnesium is added to dilute sulfuric acid. Explain two reasons for this difference.