Acids, alkalis and indicatorsIB MYP Chemistry: Flashcards
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What ion do acids form in water?
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- What ion do acids form in water?
- Hydrogen ions, H⁺.
- What ion do alkalis form in water?
- Hydroxide ions, OH⁻.
- What is a base?
- A substance that can neutralise an acid.
- What is an alkali?
- A base that dissolves in water.
- What colour is litmus in acid, alkali and neutral solutions?
- Red in acid, blue in alkali, purple in neutral.
- What colour is universal indicator in a neutral solution?
- Green.
- What does universal indicator show that litmus does not?
- How strongly acidic or alkaline a solution is.
- What is made when an acid reacts with a reactive metal?
- A salt and hydrogen.
- How do you test for hydrogen?
- A lit splint burns with a squeaky pop.
- What is made when an acid reacts with a carbonate?
- A salt, water and carbon dioxide.
- What is the ionic equation for neutralisation?
- H⁺ + OH⁻ → H₂O
- What is a strong acid?
- An acid that ionises completely in water.
- Give an example of a weak acid.
- Ethanoic acid (or citric acid).
Exam questions on Acids, alkalis and indicators
- Students at a school in Singapore test four household liquids with litmus paper: lemon juice, vinegar, soapy water and oven cleaner.Soapy water is an alkali. State what happens to red litmus paper in soapy water and name the ion that makes the solution alkaline.2 marks
- A student compares two acids of the same concentration. Hydrochloric acid turns universal indicator red, but ethanoic acid turns it orange-yellow. When identical strips of magnesium ribbon are added, bubbles of gas appear much faster in the hydrochloric acid than in the ethanoic acid.Identify two control variables that the student must keep the same for a fair comparison of the two acids.2 marks
- A science teacher in Nairobi makes an indicator by boiling red cabbage leaves in water. She adds a few drops to three colourless liquids: lemon juice turns it pink, distilled water leaves it purple, and a solution of washing soda turns it green. Later, the class compares the cabbage indicator with litmus paper and universal indicator.State what the results show about each of the three liquids.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).