The Detective's Technique
📖 The Detective's Technique
Titration is like perfectly balancing a see-saw. You carefully add weight to one side (drip by drip) until it's exactly balanced with the other. The moment it tips (colour changes) is when you've added exactly the right amount. One drop too many and you've overshot — that's why you add slowly at the end!
A titration is a technique where you add one solution (of known concentration) to another solution (of unknown concentration) until the reaction is complete. By measuring exactly how much you added, you can calculate the unknown concentration.
The genius of titration is in how you know when the reaction is complete. You add an indicator — a chemical that changes colour at the exact moment all the acid has reacted with all the alkali (the equivalence point). When you see the colour change, you stop immediately!
The key equipment:
- Burette — graduated tube with tap, measures to ±0.05 cm³ precision
- Pipette — transfers exact fixed volume (e.g., 25.0 cm³)
- Conical flask — holds the solution being titrated
- Indicator — shows when reaction is complete (e.g., phenolphthalein, methyl orange)
Chemistry glossary
- What is a titration?
- A technique to find an unknown concentration by adding a solution of known concentration until the reaction is complete You measure exactly how much was added
- What are concordant results?
- Titration results within 0.10 cm³ of each other These are the reliable results used to calculate the mean
The key idea behind titration is that neutralisation happens in a fixed mole ratio. For hydrochloric acid reacting with sodium hydroxide, the ratio is exactly 1:1. For sulfuric acid and sodium hydroxide, it is 1:2. The balanced equation tells you this ratio.
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🧠 Memory Aids
Equipment placement: "BURETTE = BASE (usually), conical flask = ACID" — though either way round works, examiners most commonly set up the base in the flask and acid in the burette, or describe acid in the burette. The key is that the solution of unknown concentration goes in the flask, measured by pipette.
Indicator colours:
- Phenolphthalein: colourless in acid → PINK in alkali. Remember: "Phenol turns PINK in base."
- Methyl orange: RED in acid → yellow in alkali. Remember: "Methyl goes RED in acid."
- Litmus: red in acid, blue in alkali (not used in titrations — colour change is not sharp enough).
Titration calculation: "n = c × V, then RATIO, then c = n ÷ V" — three steps, always in that order.
Now try it yourself
Quiz · Question 1 of 22
What is the purpose of a titration?
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This topic in real past papers
Every real exam question we've found on titrations (ht), with a full worked answer.