The starting reaction mixture has no colour. State what is seen as this reaction takes place.
Suggest why the reaction comes to an end when the sample is added to calcium carbonate.
Suggest why the calcium carbonate is in powdered form.
State what is seen when a sample of the reaction mixture is added to calcium carbonate.
Plot the results on the grid.
Draw a circle round the anomalous point on the grid.
Use the points to draw a curve of best fit.
Use the graph to find the volume of aqueous sodium thiosulfate needed for a sample taken at $250\,\text{s}$.
Use the graph to find the time at which a sample is taken if $6.0\,\text{cm}^3$ of aqueous sodium thiosulfate is required.
Describe and explain the difference between the slope of your curve at $50$ seconds and at $400$ seconds.