IGCSE Chemistry 2020 0620/61 May/June

IGCSE 2020 0620/61 May/June (pdf)

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1. A student investigated the dyes contained in different coloured inks using chromatography. Water was the solvent. The diagram shows how the student set up the apparatus.
   (a) Identify two errors in the way the student set up the apparatus.
   (b) The student then carried out the chromatography correctly.
   The diagram shows the results.
   (i) Which ink contains the greatest number of soluble dyes?
   (ii) Which two inks are made of a single soluble dye?
   (iii) From the chromatogram it is not possible to tell if the red ink contains different dyes.
   Suggest how the experiment could be changed to find out if the red ink contains different dyes.
   
2. A student investigated the reaction between dilute hydrochloric acid and two different aqueous solutions of sodium carbonate, solution E and solution F.
   Three experiments were done.
   (a) Experiment 1
   

• A burette was filled up to the 0.0cm³ mark with dilute hydrochloric acid.
• Using a measuring cylinder, 25cm³ of solution E was poured into a conical flask.
• Five drops of thymolphthalein indicator were added to the conical flask.
• Dilute hydrochloric acid was slowly added from the burette to the conical flask, while the flask was swirled, until the solution just changed colour.
  Use the burette diagrams to complete the table for Experiment 1.
  Experiment 2
  
• The conical flask was emptied and rinsed with distilled water.
  
• The burette was refilled with dilute hydrochloric acid.
  
• Experiment 1 was repeated using five drops of methyl orange indicator instead of thymolphthalein indicator.
  Use the burette diagrams to complete the table for Experiment 2.
  Experiment 3
  
• The conical flask was emptied and rinsed with distilled water.
  
• The burette was refilled with dilute hydrochloric acid.
  
• Using a measuring cylinder, 25cm³ of solution F was poured into the conical flask.
  
• Five drops of methyl orange indicator were added to the conical flask.
  
• Dilute hydrochloric acid was slowly added from the burette to the conical flask, while the flask was swirled, until the solution just changed colour.
  Use the burette diagrams to complete the table for Experiment 3.
  (b) What colour change was observed in the conical flask in Experiment 2?
  (c) Compare the volumes of dilute hydrochloric acid added in Experiment 2 and Experiment 3. Explain any difference.
  (d) Determine the simplest whole number ratio of volumes of dilute hydrochloric acid used in Experiments 1 and 2.
  (e) What volume of dilute hydrochloric acid would be required if Experiment 3 was repeated using thymolphthalein indicator instead of methyl orange indicator?
  (f) The conical flask was rinsed with distilled water between each experiment.
  (i) Why was the conical flask rinsed?
  (ii) Why does it not matter if a little distilled water is left in the flask after it has been rinsed?
  (g) State two sources of error in the experiments. For each error suggest an improvement that would reduce the error.

3. Two solids, solid G and solid H, were analysed. Solid G was copper(II) carbonate.
   Tests were done on each solid.
   tests on solid G
   Complete the expected observations.
   (a) Solid G was placed in a boiling tube. An excess of dilute sulfuric acid was added to the boiling tube. Any gas produced was tested.
   (b) Identify the gas produced in (a).
   (c) Aqueous ammonia was added slowly until in excess to the solution produced in (a). tests on solid H
   Tests were done and the following observations were made.
   (d) What conclusion can be made from the result of test 3?
   (e) What conclusions can be made about solid H from the results of test 1, test 2 and test 4?
   
4. Cobalt, manganese and nickel are metals. They react with dilute hydrochloric acid to form hydrogen gas.
   Plan an investigation to find the order of reactivity of these three metals.
   You are provided with:
   

• samples of each metal
• dilute hydrochloric acid
• common laboratory apparatus.
  Your plan must make it clear how your investigation will be a fair test and how you will use your results to place the metals in order of reactivity.

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