Concentration and rate: practical using end point method
I can carry out a fair test to investigate how the rate of reaction depends on the concentration of a reacting solution.
Concentration and rate: practical using end point method
I can carry out a fair test to investigate how the rate of reaction depends on the concentration of a reacting solution.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- The reaction between sodium thiosulfate solution and hydrochloric acid produces a cloudy precipitate.
- At the end point of the disappearing cross experiment, each reaction has produced the same amount of product.
- At the end point of the disappearing cross experiment, the chemical reaction may not be complete.
- Increasing concentration of a reacting solution introduces more reactant particles, so they collide more frequently.
Keywords
Rate of reaction - Rate of reaction is the speed with which a chemical reaction takes place.
End point method - An end point method is used to measure the progress of a reaction until it has reached completion or a desired point e.g. a colour change.
Precipitate - A precipitate is an insoluble solid formed when two solutions react together.
Fair test - In a fair test variables are controlled so that only one change affects the dependent variable.
Common misconception
The reaction stops when the 'X' is no longer visible.
The disappearance of the cross only indicates that the sulfur precipitate has formed sufficiently to obscure the cross. The reaction itself continues beyond this point until all reactants are consumed.
Equipment
Conical flask, card marked with an 'X', measuring cylinders, different concentrations of sodium thiosulfate, hydrochloric acid, timer and eye protection.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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