why is a lid used in a chromatography experiment, and why do the colours travel different distances up the paper?
3 answers
A top is used to keep evaporation of the solvent to a minimum. Different substances travel different distances because each substance has a different adsorbance to the stationary and moving phases.
Why is potespium is not kmnos his own indicator?
Because potassium permanganate has a deep violet colour which is highly visible to the naked eye and when one titrates it and there is a loss of colour, it is apparent. So one does not need an indicator to tell you the end point.