AQA GCSE Chemistry Paper 2 Higher November 2020 question paper 8462/2H

This question is about chemical analysis.

A student tested copper sulfate solution and calcium iodide solution using flame tests. This is the method used.

1. Dip a metal wire in copper sulfate solution.

2. Put the metal wire in a blue Bunsen burner flame.

3. Record the flame colour produced.

4. Repeat steps 1 to 3 using the same metal wire but using calcium iodide solution.

What flame colour is produced by copper sulfate solution?

Calcium compounds produce an orange-red flame colour. The student left out an important step before reusing the metal wire. The student’s method did not produce a distinct orange-red flame colour using calcium iodide solution. Explain why.

The student added sodium hydroxide solution to:

• copper sulfate solution

• calcium iodide solution.

Give the results of the tests. Copper sulfate solution

Calcium iodide solution

To test for sulfate ions the student added dilute hydrochloric acid to copper sulfate solution. Name the solution that would show the presence of sulfate ions when added to this mixture.

To test for iodide ions the student added dilute nitric acid to calcium iodide solution. Name the solution that would show the presence of iodide ions when added to this mixture. Give the result of the test.

This question is about water.

In the UK, potable (drinking) water is produced from different sources of fresh water. Explain how potable water is produced from fresh water.

A different country has:

• very little rainfall

• a long coastline

• plentiful energy supplies.

Suggest one process this country could use to obtain most of its potable water.

Waste water is not fit to drink. Treatment of waste water produces two substances:

• liquid effluent

• solid sewage sludge.

Draw one line from each substance to the way the substance is processed.

Substance Process

Table 1 shows information about the disposal of processed solid sewage sludge in the UK in 1992 and in 2010.

Calculate the percentage of processed solid sewage sludge that was burned in 2010. Give your answer to 3 significant figures. Use Table 1.

Suggest one reason why the total mass of processed solid sewage sludge increased between 1992 and 2010.

Between 1992 and 2010 the proportion of processed solid sewage sludge used as fertiliser increased. Suggest two reasons why.

This question is about hydrocarbons. Hexane and hexene are hydrocarbons containing six carbon atoms in each molecule. Hexane is an alkane and hexene is an alkene.

Draw one line from each hydrocarbon to the formula of that hydrocarbon.

Bromine water is added to hexane and to hexene. What would be observed when bromine water is added to hexane and to hexene?

Ethane is an alkane and ethene is an alkene. Figure 1 shows the displayed structural formulae of ethane and of ethene.

Compare ethane with ethene. You should refer to:

• their structure and bonding

• their reactions.

This question is about ink. A student investigated green ink using paper chromatography in a beaker. The student used water as the solvent.

Figure 2 shows the chromatogram obtained.

Figure 2

The R_f value of the yellow dye = 0.60 The distance moved by the yellow dye = 5.7 cm Calculate the distance moved by the solvent.

The green ink contains more than two compounds. Suggest one reason why only two spots are seen on Figure 2.

On the student’s chromatogram, the yellow and blue spots are very close together. Which two ways could increase the distance between the spots? Tick (✓) two boxes.

The manufacturers of the green ink always use the same proportions of yellow dye and blue dye. Suggest one reason why.

The R_f value of a dye depends on:

• the solubility of the dye in the solvent

• the attraction of the dye to the paper.

Which will definitely produce a smaller R_f value if the solvent and paper are both changed? Tick (✓) one box.

The dye is more soluble in the new solvent and more attracted to the new paper. 8

This question is about materials used to make food plates. Food plates are made from paper, polymers or ceramics.

Table 2 shows information about plates of the same diameter made from each of these materials.

Table 2 does not show information about energy usage. Suggest two pieces of information about energy usage which would help to produce a complete life cycle assessment (LCA) for the three food plate materials.

Evaluate the use of these materials for making food plates. You should use features of life cycle assessments (LCAs). Use Table 2.

Describe how ceramic food plates are produced from clay.

This question is about atmospheric pollution.

Figure 3 shows a limestone carving which has been damaged by atmospheric pollution. The carving has been:

• blackened by soot

• eroded where the limestone has reacted with atmospheric pollutants.

Explain why soot is formed when some fossil fuels are burned.

Fossil fuels are burned in car engines. Explain how reducing the amount of sulfur in fossil fuels reduces the erosion of limestone.

Oxides of nitrogen are atmospheric pollutants which are formed in car engines. Explain why oxides of nitrogen are formed in car engines.

This question is about carboxylic acids. Carboxylic acids belong to a homologous series. Table 3 shows information about the first three carboxylic acids in this homologous series.

Complete Table 3.

Ethanoic acid ionises in water. The equation for the reaction is:

Explain how the equation shows that ethanoic acid is a weak acid.

A student adds a solution of ethanoic acid to zinc carbonate in an open flask on a balance. Explain what happens to the mass of the flask and its contents during the reaction.

The student compares the rates of the reaction of zinc carbonate with:

• 0.01 mol/dm³ methanoic acid

• 0.01 mol/dm³ ethanoic acid.

The rate of the reaction with methanoic acid is greater than the rate of the reaction with ethanoic acid. Explain why. You should refer to ions in your answer. Use Table 3.

Ethanoic acid reacts with ethanol to produce an ester.

Give the name of the ester produced when ethanoic acid reacts with ethanol.

Hexanedioic acid and ethanediol join together to produce a polyester. Ethanoic acid and ethanol join together in the same way to produce an ester. Which is the displayed structural formula of the ester produced when ethanoic acid reacts with ethanol? Tick (✓) one box.

This question is about the rate of the reaction between hydrochloric acid and calcium carbonate. A student investigated the effect of changing the size of calcium carbonate lumps on the rate of this reaction. This is the method used.

1. Pour 40 cm³ of hydrochloric acid into a conical flask.

2. Add 10.0 g of small calcium carbonate lumps to the conical flask.

3. Attach a gas syringe to the conical flask.

4. Measure the volume of gas produced every 30 seconds for 180 seconds.

5. Repeat steps 1 to 4 using 10.0 g of large calcium carbonate lumps.

The student calculated the number of moles of gas from each volume of gas measured. Table 4 shows the student’s results for large calcium carbonate lumps.

The student plotted the results for small calcium carbonate lumps on Figure 4.

Complete Figure 4. You should:

• plot the data for large calcium carbonate lumps from Table 4

• draw a line of best fit.

Determine the mean rate of reaction for small calcium carbonate lumps between 20 seconds and 105 seconds. Give the unit. Use Figure 4.

The student concluded that the large calcium carbonate lumps reacted more slowly than the small calcium carbonate lumps. How do the student’s results show that this conclusion is correct?

The difference in the rates of reaction of large lumps and of small lumps of calcium carbonate depends on the surface area to volume ratios of the lumps. Figure 5 shows a cube of calcium carbonate.

Calculate the surface area to volume ratio of the cube in Figure 5. Give your answer as the simplest whole number ratio.

A larger cube of calcium carbonate has sides of 5 cm Describe how the surface area to volume ratio of this larger cube differs from that of the cube shown in Figure 5.

This question is about algae. A student:

• placed algae in water containing dissolved carbon dioxide

• shone bright light on the algae.

Gas bubbles were collected as the algae photosynthesised.

Describe a test that would identify the gas collected. Give the result of the test.

Glucose is produced when algae photosynthesise. Name two naturally occurring polymers produced from glucose.

Figure 6 shows the displayed structural formula of an amino acid called glycine.

Figure 6

How many functional groups are there in the molecule in Figure 6 ? Tick (✓) one box.

Glycine reacts by condensation polymerisation to produce a polypeptide and one other substance. Name the other substance produced.

Scientists think that algae may have used gases in Earth’s early atmosphere. Algae need an element to produce the molecule in Figure 6 which is not present in water or carbon dioxide. Which two gases from Earth’s early atmosphere could have provided this element?

The development and function of algae are controlled by a naturally occurring polymer. Figure 7 represents the shape and structure of this polymer.

Describe the shape and structure of this polymer.

This question is about a reversible reaction. The reaction between solutions of iron(III) ions (Fe³⁺) and thiocyanate ions (SCN^–) is reversible. The ionic equation for the reaction is:

Colour of solution: yellow colourless red The colour of the equilibrium mixture is orange at room temperature.

Give the name of the solvent used to dissolve the ions in this reaction.

A few drops of a colourless solution containing a high concentration of thiocyanate ions (SCN –) are added to the orange equilibrium mixture. Explain the colour change observed.

A water bath is set up at a temperature above room temperature. When a test tube containing the orange equilibrium mixture is placed in the water bath, the mixture becomes more yellow. Explain what this shows about the energy change for the forward reaction.

Explain why a change in pressure does not affect the colour of the equilibrium mixture.

Other metal ions form coloured equilibrium mixtures with thiocyanate ions. Which metal ion could form a coloured equilibrium mixture with thiocyanate ions? Tick (✓) one box.