Chemical ChangesAQA GCSE Chemistry: Topic test

20 questions, 54 marks

AQA GCSE Chemistry

Chemical Changes topic test

Total 54 marks

Name

Class

Date

1
A metal recycling company receives mixed scrap containing compounds of zinc, iron and copper. Before investing in new equipment, the company researches whether each metal could be economically extracted from its oxide by heating with carbon, based on each metal's position in the reactivity series.
(a)
Metals less reactive than carbon can be extracted from their oxides by heating with carbon. Which term describes this type of reaction, in which oxygen is removed from the metal oxide?
[1 mark]
AReduction
BOxidation
CNeutralisation
DElectrolysis
(b)
Zinc and iron are both less reactive than carbon, so both can be extracted from their oxides by heating with carbon. Which of these metals is found as the metal itself in the ground, requiring no chemical extraction at all?
[1 mark]
AZinc
BGold
CIron
DCopper
(c)
Copper is less reactive than carbon. Write a word equation for the extraction of copper from copper oxide by heating with carbon, and name the gas produced.
[2 marks]
Total for question 1: 4 marks
2
A boat manufacturer tests which metal, magnesium, zinc or copper, would work best as a sacrificial anode to protect a steel boat hull from corrosion in seawater, by reacting samples with dilute hydrochloric acid to compare their rate of reaction and observe which metals react at all.
(a)
Magnesium reacts vigorously with dilute hydrochloric acid, fizzing rapidly, while zinc reacts more slowly, and copper does not react at all. Which gas is produced when magnesium reacts with the acid?
[1 mark]
AOxygen
BCarbon dioxide
CHydrogen
DChlorine
(b)
Why does copper not react with dilute hydrochloric acid, unlike magnesium and zinc?
[1 mark]
ACopper is more reactive than hydrogen, so it displaces hydrogen easily
BCopper does not contain any electrons
CCopper reacts only with concentrated acids
DCopper is less reactive than hydrogen, so it cannot displace hydrogen from the acid to form ions
(c)
Based on these observations, place magnesium, zinc and copper in order of decreasing reactivity, and explain how the manufacturer could use this order to choose the best sacrificial anode metal to protect the steel hull.
[2 marks]
Total for question 2: 4 marks
3
A specialist chemical supplier prepares pure, dry crystals of magnesium sulfate (Epsom salts) for a wellness product company, by reacting excess magnesium oxide, an insoluble base, with dilute sulfuric acid, before filtering, evaporating and crystallising the resulting solution.
(a)
Write a word equation for the reaction between magnesium oxide and dilute sulfuric acid, and describe why excess magnesium oxide is added to the acid.
[3 marks]
(b)
Describe the remaining steps the supplier would carry out after filtering off the excess magnesium oxide, to obtain pure, dry crystals of magnesium sulfate from the filtered solution.
[4 marks]
Total for question 3: 7 marks
4
An aluminium recycling and extraction company operates two processes: extracting new aluminium from aluminium oxide ore by electrolysis, and, in a separate part of the plant, purifying scrap copper by electrolysis of copper sulfate solution using impure copper electrodes.
(a)
Explain why aluminium cannot be extracted from aluminium oxide by heating with carbon, unlike iron or copper, and why electrolysis is used instead. Include the environmental or economic factor that makes this method expensive.
[6 marks]
(b)
Describe what happens at each electrode during the electrolysis of copper sulfate solution when purifying scrap copper, using an impure copper anode (positive electrode) and a strip of pure copper as the cathode (negative electrode), and explain why this method is chosen to purify the copper rather than using inert electrodes.
[6 marks]
Total for question 4: 12 marks
5
A hydroponics farm monitors the pH of its nutrient solution using a digital pH probe, since crops grow best within a narrow pH range, and adjusts the solution using small amounts of dilute acid or alkali when readings drift outside this range.
(a)
The farm's nutrient solution has a pH of 5. What does this indicate about the solution?
[1 mark]
AIt is acidic, since a pH below 7 indicates an acidic solution
BIt is alkaline, since a pH below 7 indicates an alkaline solution
CIt is neutral
DIt cannot be determined from the pH alone
(b)
The farm adds a small amount of dilute potassium hydroxide solution, an alkali, to raise the pH of the nutrient solution. Which ion, present in all alkaline solutions, causes this increase in pH?
[1 mark]
AH+
BOH-
CK+
DCl-
(c)
Write an ionic equation for the neutralisation reaction that occurs when the alkali reacts with excess acid in the nutrient solution.
[2 marks]
Total for question 5: 4 marks
6
A printed circuit board manufacturer electrolyses waste copper chloride solution, left over from etching circuit boards, using inert graphite electrodes, to recover copper metal and produce chlorine gas, before safely disposing of the remaining solution.
(a)
During electrolysis, positively charged ions move to one electrode and negatively charged ions move to the other. Which electrode do the positively charged copper ions move to?
[1 mark]
AThe anode, because it is negatively charged
BThe anode, because it is positively charged
CThe cathode, because it is negatively charged
DThe cathode, because it is positively charged
(b)
At the anode (positive electrode), chloride ions are discharged to form chlorine gas. What happens to the chloride ions during this process?
[1 mark]
AThey gain electrons
BThey gain protons
CThey split into chlorine and hydrogen
DThey lose electrons
(c)
Explain why inert graphite electrodes, rather than reactive metal electrodes, are used in this electrolysis process.
[2 marks]
Total for question 6: 4 marks
7
A jewellery cleaning company investigates recovering silver from waste photographic/cleaning solution containing dissolved silver nitrate, by adding coils of copper wire to the solution and observing the reaction that follows over several hours.
(a)
Copper is more reactive than silver. Predict and explain what would be observed when copper wire is added to the silver nitrate solution, and write a word equation for the reaction.
[3 marks]
(b)
Explain, in terms of electron transfer, why this is described as a displacement reaction, and identify which species is oxidised and which is reduced.
[4 marks]
Total for question 7: 7 marks
8
A chemistry teacher sets a project comparing three metals, aluminium, zinc and copper, exploring both how each metal is industrially extracted from its ore and how each metal reacts, or fails to react, with dilute sulfuric acid, to help students connect a metal's position in the reactivity series with both its extraction method and its chemical behaviour.
(a)
Explain, in terms of the reactivity series, why aluminium must be extracted by electrolysis while zinc and copper can both be extracted by reduction with carbon, even though these three metals have quite different reactivities from each other.
[6 marks]
(b)
The students react small, equal-sized samples of zinc and copper with dilute sulfuric acid. Predict and explain, in terms of the reactivity series, what would be observed with each metal, and write a balanced symbol equation for any reaction that occurs.
[6 marks]
Total for question 8: 12 marks

End of questions