Acids, bases and neutralisation Edexcel International GCSE Chemistry revision
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In plain words
Acids are the sour, sharp ones: lemon juice, vinegar, stomach acid. Alkalis are their opposites: soapy things such as oven cleaner. Mix the right amounts and they cancel each other out, leaving a salt and water. The pH scale says which you have: below 7 acid, 7 neutral, above 7 alkali.
Three things to know
- Acids give H⁺ ions in water and have a pH below 7. Alkalis (bases that dissolve) give OH⁻ ions and have a pH above 7. Litmus is red in acid and blue in alkali; methyl orange is red in acid and yellow in alkali.
- Acid + metal → salt + hydrogen. Acid + base (a metal oxide or hydroxide) → salt + water. Acid + carbonate → salt + water + carbon dioxide.
- Neutralisation is H⁺ + OH⁻ → H₂O. A strong acid (hydrochloric) splits up completely into ions in water; a weak acid (ethanoic) only partly.
Worked example
Name the salt made when zinc oxide reacts with sulfuric acid, and the other product.
- The first part of the name comes from the metal: zinc.
- The second part comes from the acid: sulfuric acid makes sulfates.
- Zinc sulfate, and water (acid + base → salt + water).
Tips and tricks
- Naming salts: hydrochloric acid makes chlorides, sulfuric acid makes sulfates, nitric acid makes nitrates.
- Fizzing with an acid means a gas. A metal gives hydrogen; a carbonate gives carbon dioxide.
It lands in your notebook with its questions as flashcards.
Acids, bases and neutralisation: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is the pH of a neutral solution?
Below 7 is acidic, above 7 is alkaline.
Which ion makes a solution acidic?
All acids release hydrogen ions in water.
Which gas is made when an acid reacts with a carbonate?
Acid + carbonate → salt + water + carbon dioxide.
What colour is methyl orange in an acid?
It is red in acid and yellow in alkali.
What are the products when sodium hydroxide reacts with hydrochloric acid?
Acid + alkali → salt + water.
Which of these is a weak acid?
It only partly splits into ions in water.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 8 marks. Write your answers on paper, then check them.
Acids, bases and neutralisation
Edexcel International GCSE Chemistry 4CH1 · 8 marks · papermunch.org
Name ______________________________ Date ______________
Name the products of the reaction between magnesium and hydrochloric acid, and write the balanced equation.[2]
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Magnesium chloride and hydrogen. Mg + 2HCl → MgCl₂ + H₂.
Write the ionic equation for neutralisation.[1]
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H⁺ + OH⁻ → H₂O.
Calcium carbonate is added to dilute hydrochloric acid. State what you would see and name the three products.[3]
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Fizzing (bubbles of gas), and the solid disappears. Calcium chloride, water and carbon dioxide.
State the difference between a strong acid and a weak acid.[2]
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A strong acid is completely dissociated (ionised) in water; a weak acid is only partly dissociated.
Answers: Acids, bases and neutralisation
- 1. Magnesium chloride and hydrogen. Mg + 2HCl → MgCl₂ + H₂.
- 2. H⁺ + OH⁻ → H₂O.
- 3. Fizzing (bubbles of gas), and the solid disappears. Calcium chloride, water and carbon dioxide.
- 4. A strong acid is completely dissociated (ionised) in water; a weak acid is only partly dissociated.