u haf to see the products of the reaction. different products
haf different colours(mainly transitional metal ions). the common
ones r Cu2+, Cu3+, Fe3+, Fe2+....otherwise is according to acidity
or oxidation.
acidity:depending on indicator used, different indicators haf
different colour changes. for example, phenolthalein will b pink in
acidic medium n colourless in basic mediums.(used to check end
point of neutralisation titrations)
oxidation:usually using KMnO4. if solution undergoes oxidation, it
will decolourise purple KMnO4. K2Cr2O7 is used sometimes as well.
also decolourises when solution gets oxidised.
