Brainlag PlusThe Edexcel core practical: adding calcium hydroxide or calcium oxide to dilute hydrochloric acid a little at a time, measuring the pH, and explaining the shape of the graph.
What happens
Calcium hydroxide and calcium oxide are bases.
Each neutralises hydrochloric acid to make calcium chloride, a salt.
- Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O
- CaO + 2HCl → CaCl₂ + H₂O
- in both: H⁺ + OH⁻ → H₂O (calcium oxide makes OH⁻ ions when it meets water)
You add the powder a little at a time to a fixed volume of acid and measure the pH after each portion.
- Independent variable: the total mass of base added.
- Dependent variable: the pH.
- Control variables: the volume and concentration of the acid, the size of each portion, the temperature at the start.
The rest of this lesson and its 9 practice questions are in Plus.
Screen 1 of 4, free to read.
- 9 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards