Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Elements, Compounds and Mixtures
69 practice questions
Topics covered
Practice questions
21–30 of 69
Question 21
3 marks · Easy
Answer and see the solution →A student has a mixture of iron filings and sulfur powder. They want to separate the two substances.
(a)[1 mark]State one physical property that can be used to separate iron filings from sulfur powder.
(b)[1 mark]Describe the separation technique they should use.
(c)[1 mark]Explain why this technique does not work for separating iron that has chemically reacted with sulfur.
Question 22
2 marks · Easy
Answer and see the solution →Explain why crystallisation is a good technique for separating sodium chloride from its aqueous solution.
Question 23
1 mark · Easy
Answer and see the solution →State the name of the technique used to separate an insoluble solid from a liquid.
Question 24
3 marks · Easy
Answer and see the solution →The diagram shows the apparatus used for simple distillation.
Apparatus for simple distillation (a)[1 mark]Name the liquid collected in the beaker.
(b)[1 mark]Give the name of the process shown.
(c)[1 mark]Explain why the salty water is heated in this process.
Question 25
2 marks · Easy
Answer and see the solution →A mixture of water and ethanol is heated. Water has a boiling point of 100°C and ethanol has a boiling point of 78°C. If the thermometer reads 78°C while distillate is being collected, which liquid is distilling over? Calculate how many degrees lower this temperature is than the boiling point of water.
Question 26
2 marks · Easy
Answer and see the solution →A sample of rock salt contains 16 g of sodium chloride mixed with 4 g of insoluble impurities. A student dissolves the sample in water, filters the solution, and then uses crystallisation to obtain sodium chloride crystals. What is the maximum mass of sodium chloride crystals the student can expect to obtain after crystallisation? Assume no losses occur during the process.
Question 27
3 marks · Easy
Answer and see the solution →A student carries out chromatography to separate the dyes in two different food colourings, X and Y. The chromatogram below shows the results. Each spot represents a dye.
Chromatogram showing dyes in colourings X and Y (solvent front at 10 cm, start line at 0 cm, each dye marked as a spot). (a)[1 mark]How many different dyes are present in colouring X?
(b)[1 mark]Which dye(s) are found in both X and Y?
(c)[1 mark]Suggest why one dye in X reached the top of the chromatogram while another travelled only a short distance.
Question 28
2 marks · Normal
Answer and see the solution →State one separation technique that could be used to obtain pure water from salty water, and one technique that could be used to obtain pure salt from salty water.
Question 29
4 marks · Normal
Answer and see the solution →(a)[2 marks]Describe the steps needed to obtain pure crystals of copper sulfate from a mixture of copper sulfate and sand.
(b)[2 marks]Explain why filtration is a necessary step in this process.
Question 30
3 marks · Normal
Answer and see the solution →Explain why fractional distillation is able to separate ethanol from water, but simple distillation cannot produce pure ethanol from the mixture.