Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Carboxylic Acids
48 practice questions
Topics covered
Practice questions
21–30 of 48
Question 21
3 marks · Easy
Answer and see the solution →Ethanoic acid is a weak acid.
(a)[1 mark]State the colour change seen when blue litmus paper is placed in ethanoic acid.
(b)[2 marks]Explain what is meant by the term "weak acid".
Question 22
2 marks · Easy
Answer and see the solution →A student reacts 0.81 g of magnesium with excess butanoic acid. Calculate the maximum volume of hydrogen gas produced at room temperature and pressure. (1 mol of any gas occupies 24 dm³ at r.t.p.; Mg = 24.3 g/mol)
Question 23
2 marks · Easy
Answer and see the solution →Explain why carboxylic acids such as ethanoic acid have a higher pH than hydrochloric acid of the same concentration.
Question 24
1 mark · Easy
Answer and see the solution →State the products formed when dilute butanoic acid reacts with magnesium metal.
Question 25
3 marks · Easy
Answer and see the solution →Ethanoic acid is a weak acid. A student places blue litmus paper into a solution of ethanoic acid and measures the pH.
(a)[1 mark]State the expected colour change of the litmus paper.
(b)[1 mark]Ethanoic acid reacts with sodium carbonate solution. Write the chemical name of the gas produced.
(c)[1 mark]Describe what is meant by a 'weak acid' in terms of ionisation in water.
Question 26
2 marks · Easy
Answer and see the solution →A student reacts 1.2 g of magnesium with excess propanoic acid.
Calculate the maximum volume of hydrogen gas produced at room temperature and pressure. (Molar mass of Mg = 24 g/mol, 1 mol gas = 24 dm³ at r.t.p.)
Question 27
2 marks · Normal
Answer and see the solution →State the products formed when magnesium metal reacts with dilute propanoic acid. Write a balanced chemical equation for this reaction.
Question 28
4 marks · Normal
Answer and see the solution →Ethanoic acid is a commonly used carboxylic acid.
(a)[1 mark]State the term used to describe the strength of ethanoic acid as an acid.
(b)[1 mark]Describe how ethanoic acid affects blue litmus paper.
(c)[1 mark]Suggest a typical pH value for a solution of ethanoic acid.
(d)[1 mark]Compare the reaction rate of magnesium with ethanoic acid to the reaction rate with hydrochloric acid. State which is faster and explain why.
Question 29
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 30
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.