Neutralisation and oxides
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 2 worked examples, 5 practice questions, 2 real past-paper questions with the answers explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Wasp or bee?
- Neutralisation
- The pH changes
Read the transcript of the teaching part
Last time
Before we start: last time, in The pH scale, indicators, strong and weak acids, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Wasp or bee?
A bee sting is acidic. A wasp sting is alkaline. Rub the wrong thing on it and you make it worse, so you need to know what neutralisation really is, and which oxides act as acids and which as bases.
Neutralisation
Neutralisation is the reaction of an acid with a base to give a salt and water. The ionic equation is always the same: H plus plus OH minus gives H 2 O. The hydrogen ions of the acid are used up by the hydroxide ions of the alkali.
The pH changes
Start with an acid: the pH is low. As alkali is added, the pH rises. When exactly enough alkali has been added, the mixture is neutral, pH 7. That is the end-point. More alkali makes the pH go above 7. Adding acid to alkali does the opposite.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Acidic, basic and amphoteric oxides · Acidic, basic and amphoteric oxides.
The whole chapter: Acids, Bases and Salts, Acids, Bases and Salts.
Chapter 7: Acids, bases and salts
- Properties of acids and bases, proton transfer 5 min
- The pH scale, indicators, strong and weak acids 6 min
- Neutralisation and oxides 6 min
- Making soluble and insoluble salts, hydrated salts 6 min
Also for IGCSE Chemistry 0620
Which topics come up most in IGCSE Chemistry 0620 past papers, counted from every paper since 2004.