Question 1 Medium
Balance the equation: __ HCl + __ CaCO₃ → __ CaCl₂ + __ H₂O + __ CO₂. Give the numbers in order, separated by commas.
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Answer: 2, 1, 1, 1, 1
- Calcium: 1 on each side.
- 2 HCl gives 2 Cl for CaCl₂.
- 2, 1, 1, 1, 1
Acids, bases and making salts: GCSE Combined Science Chemistry practice questions
A second set of questions on acids, bases and making salts. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
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Question 2 Medium
Why is a solution of copper oxide in sulfuric acid blue?
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Answer: copper sulfate forms
- They make copper sulfate.
- Copper(II) compounds are blue.
Question 3 Medium
Name the two products when zinc oxide reacts with hydrochloric acid.
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Answer: zinc chloride and water
- A metal oxide and an acid make a salt and water.
- Hydrochloric acid makes a chloride.
Question 4 Medium
Write the balanced equation for magnesium reacting with hydrochloric acid.
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Answer: Mg + 2HCl → MgCl₂ + H₂
- A metal and an acid make a salt and hydrogen.
- Magnesium chloride is MgCl₂, so 2HCl is needed.
Question 5 Hard
Write the ionic equation for neutralisation.
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Answer: H⁺ + OH⁻ → H₂O
- Hydrogen ions react with hydroxide ions.
- The product is water.
Question 6 Hard
Describe one way to get dry crystals from copper sulfate solution without heating to dryness.
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Answer: evaporate some of the water then leave to cool
- Evaporate some water.
- Leave to cool so crystals form.
Question 7 Hard
A student wants to make silver chloride. Explain why precipitation is used rather than adding an excess of insoluble base to acid.
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Answer: silver chloride is insoluble so it forms as a precipitate when two solutions are mixed
- Silver chloride is insoluble.
- Precipitation mixes two solutions to make the solid.
Question 8 Hard
Why is sodium hydroxide not added in excess when making sodium chloride crystals?
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Answer: it is soluble so the excess cannot be filtered off
- Sodium hydroxide is soluble.
- The excess cannot be filtered off.
Question 9 Medium
What colour is phenolphthalein in an alkali?
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Answer: pink
- Phenolphthalein is colourless in acid.
- In alkali it is pink.
Question 10 Medium
What colour is methyl orange in an acid?
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Answer: red
- Methyl orange is red in acid.
- It turns yellow in alkali.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What ion do acids make in water?
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Hydrogen ions, H⁺.
Check 2
What ion do alkalis make in water?
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Hydroxide ions, OH⁻.
Check 3
What is a base?
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A substance that neutralises an acid.
Check 4
What is an alkali?
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A base that dissolves in water.
Check 5
What is the pH of a neutral solution?
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7.
Check 6
What colour is universal indicator in a strong acid?
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Red.
Check 7
What colour is litmus in an alkali?
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Blue.
Check 8
What is neutralisation?
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An acid reacting with a base to make a salt and water.
Check 9
What is the ionic equation for neutralisation?
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H⁺ + OH⁻ → H₂O.
Check 10
What does acid + metal make?
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A salt and hydrogen.
Check 11
What does acid + carbonate make?
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A salt, water and carbon dioxide.
Check 12
What salt does hydrochloric acid make?
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A chloride.
Check 13
What salt does sulfuric acid make?
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A sulfate.
Check 14
What salt does nitric acid make?
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A nitrate.
Check 15
Why is an insoluble base added in excess?
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So all the acid reacts and the excess can be filtered off.
Check 16
How do you make an insoluble salt?
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Mix two solutions to precipitate it, then filter.
Check 17
What does the pH scale measure?
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How acidic or alkaline a solution is, on a scale from 0 to 14.
Check 18
What colour is phenolphthalein in an alkali?
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Pink. It is colourless in acid.
Check 19
What is a salt?
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A compound made when the hydrogen in an acid is replaced by a metal.
Check 20
What is a precipitate?
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An insoluble solid that forms when two solutions are mixed.
Check 21
What is the filtrate?
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The liquid that passes through the filter paper.
Check 22
What does acid + metal oxide make?
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A salt and water.
Check 23
How do you test for carbon dioxide?
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Bubble the gas through limewater. It turns milky.
Check 24
Which salts are all soluble in water?
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All nitrates, and all sodium, potassium and ammonium salts.
Check 25
Why do indigestion tablets work?
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They neutralise extra acid in the stomach.
Check 26
What colour is litmus in acid and in alkali?
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Red in acid and blue in alkali.
Check 27
What colour is methyl orange in acid and in alkali?
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Red in acid and yellow in alkali.
Check 28
What colour is phenolphthalein in acid and in alkali?
Show answer
Colourless in acid and pink in alkali.
Keep going with Acids, bases and making salts
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