AQA GCSE Combined Science Foundation (8464), Foundation tier · Chemistry › Chemical changes › Reactions of acids
Practise Reactions of acids with metals. 5 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Acids react with some metals: metal + acid → salt + hydrogen.
You need the reactions of magnesium, zinc and iron with dilute hydrochloric acid and dilute sulfuric acid.
You see fizzing (bubbles of hydrogen) and the metal gets smaller. Magnesium reacts quickly, zinc steadily and iron slowly. Copper does not react with these acids.
Same acid, same size of metal: more bubbles per second means a more reactive metal.
Test for hydrogen: hold a lit splint at the mouth of the test tube. Hydrogen burns with a squeaky pop.
Naming salts and writing equations
Hydrochloric acid (HCl) makes chlorides. Sulfuric acid (H2SO4) makes sulfates.
Mg + 2HCl → MgCl2 + H2
Zn + H2SO4 → ZnSO4 + H2
Fe + 2HCl → FeCl2 + H2 (iron forms iron(II) chloride with dilute hydrochloric acid)
Hydrogen is a diatomic gas, so it is always written H2.
How to answer each type of question
Complete a word equation
1 to 2 marksGrade 3
The products are always a salt and hydrogen.
Name the salt: metal name first, then chloride (hydrochloric acid) or sulfate (sulfuric acid).
Example. Complete the word equation. zinc + hydrochloric acid → ................ + ................
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zinc chloride (1) + hydrogen (1)
Describe how to compare the reactivity of two metals with acid
3 to 4 marksGrade 5
Use the same mass or size of each metal.
Use the same volume and concentration of acid at the same temperature.
Say what you measure: volume of gas in a set time, rate of bubbling or temperature rise.
Say how you decide: the faster reaction shows the more reactive metal.
Example. Describe how a student could show that magnesium is more reactive than iron, using dilute sulfuric acid.
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Add the same mass / same size pieces of each metal (1) to the same volume and concentration of sulfuric acid (1) Measure the volume of hydrogen made in a set time / compare the rate of bubbling (1) Magnesium produces gas faster, so it is more reactive (1)
Don’t lose marks
Writing hydrogen as H instead of H2.
Naming salts wrongly, e.g. 'zinc hydrochloride' instead of zinc chloride.
Saying copper reacts with dilute acid to give hydrogen.
Mixing up the hydrogen test (lit splint, pop) with the oxygen test (glowing splint relights).
More tips
Memory tricks
MASH: Metal + Acid → Salt + Hydrogen.
Salt name = metal name + ending from the acid (hydrochloric → chloride, sulfuric → sulfate).
Squeaky pop = hydrogen. A glowing splint relighting is the test for oxygen, not hydrogen.
Exam technique
For observations, write 'fizzing' or 'bubbles'. 'Hydrogen is produced' is not an observation.
In practical comparisons, say what you keep the same as well as what you measure.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Name the products of metal + acidA salt and hydrogen, e.g. magnesium + hydrochloric acid → magnesium chloride + hydrogen.
Grade 4
Name the salt from the acid usedHydrochloric acid gives chlorides and sulfuric acid gives sulfates.
Grade 4
Describe the test for hydrogenA lit splint held at the mouth of the tube burns the hydrogen with a squeaky pop.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Complete the word equation. zinc + hydrochloric acid → .................... + hydrogen
zinc chloride
Write a balanced symbol equation for the reaction of magnesium with dilute sulfuric acid.
Mg + H2SO4 → MgSO4 + H2
Complete the word equation. aluminium + sulfuric acid → .................... + ....................
aluminium sulfate + hydrogen
Magnesium reacts with dilute hydrochloric acid. Bubbles of gas form and the magnesium disappears. Name the salt produced.
magnesium chloride
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Acids react with some metals to produce a salt and hydrogen.
(a) Complete the word equation. zinc + hydrochloric acid → .................... + hydrogen[1]
(b) Describe the test for hydrogen and give the result.[2]
(c) Name the salt formed when iron reacts with dilute sulfuric acid.[1]
Show the answer and mark scheme
(a)Answer: zinc chloride
zinc chloride
(b)
put a burning / lit splint at the mouth of the test tube
(burns with a) squeaky pop
(c)Answer: iron(II) sulfate
iron(II) sulfate / iron sulfate
Question 2Medium6 marks
Magnesium, zinc and iron all react with dilute hydrochloric acid and dilute sulfuric acid.
(a) Write a balanced symbol equation for the reaction of magnesium with dilute sulfuric acid.[1]
(b) Balance the equation for the reaction of iron with hydrochloric acid. Fe + ....HCl → FeCl2 + H2[1]
(c) A student added equal-sized pieces of magnesium, zinc and iron to separate test tubes containing the same volume of the same dilute hydrochloric acid. Describe how the observations would be different for the three metals.[3]
(d) Explain why copper does not react with dilute hydrochloric acid.[1]
Show the answer and mark scheme
(a)Answer: Mg + H2SO4 → MgSO4 + H2
Mg + H2SO4 → MgSO4 + H2
(b)Answer: Fe + 2HCl → FeCl2 + H2
2 (HCl)
(c)
magnesium fizzes most vigorously / produces bubbles fastest
zinc fizzes steadily / less than magnesium
iron produces bubbles slowly / least vigorous
(d)
copper is less reactive than hydrogen (so cannot displace it from the acid)