Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Organic Chemistry
785 practice questions
Topics covered
Practice questions
241–250 of 335 · Normal
Question 241
3 marks · Normal
Answer and see the solution →Vinegar contains ethanoic acid as its main component. A student finds that a 75 g bottle of vinegar contains 3.0 g of pure ethanoic acid.
Calculate the percentage by mass of ethanoic acid in this sample of vinegar. Give your answer to 2 significant figures.
Question 242
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 243
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 244
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 245
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 246
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 247
2 marks · Normal
Answer and see the solution →Give the name and the molecular formula of the carboxylic acid with three carbon atoms.
Question 248
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 249
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 250
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.