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Chemistry · Rates · Turbidity method
Rate of reaction — Na₂S₂O₃ + HCl
A paper cross is drawn on white card and a beaker of sodium thiosulfate solution is placed on top. Hydrochloric acid is added; sulfur precipitates and the solution slowly turns cloudy. Time how long it takes for the cross to disappear from view. Repeat at five different [Na₂S₂O₃].
t = 0 s
Results table
| [Na₂S₂O₃] | t (s) | rate × 1000 (s⁻¹) |
|---|---|---|
| 0.05 M | — | — |
| 0.10 M | — | — |
| 0.15 M | — | — |
| 0.20 M | — | — |
| 0.25 M | — | — |
Rate vs [Na₂S₂O₃]
Exam-style questions
1. What causes the solution to become cloudy?
2. How is the RATE of reaction estimated in this experiment?
3. If a plot of 1/time vs [Na₂S₂O₃] gives a STRAIGHT LINE through the origin, what does that tell you?
4. Why MUST every run use the same paper cross, same beaker depth, same viewer, and same room temperature?