8: Rainbow Reactions

Neutralisation Demonstration

You will probably have used indicators in your science lessons. This Rainbow Reaction experiment uses universal indicator, a full range indicator which can measure pH from 1 to 14.

You may have already carried out work in the laboratory which shows that an acid can be neutralised (cancelled out) by an alkali of equal strength.

This Neutralisation Demonstration shows neutralisation and the range of indicator colours very effectively.

What you will need

50cm3 burette with bung
syringes to dispense up to 20cm3
very dilute sodium hydroxide solution
dilute hydrochloric acid
sodium carbonate solution
universal indicator solution
eye protection

What you do

  1. Eye ProtectionIrritant
    Make sure that the tap of your burette is closed.
    Add 10cm3 of sodium hydroxide to the burette followed by a few drops of universal indicator.
  2. Add 20cm3 of hydrochloric acid followed by 2cm3 of sodium carbonate solution.
    Insert the bung and turn the burette upside down carefully, while holding on to the bung. Be careful as gas will form and could spray over you. You should see rainbow colours ranging from deep purple through blue and green to orange and red. But if you don’t, turn the burette upside down again (carefully).
eye protection
eye protection must be worn

Irritant
IRRITANT
sodium hydroxide solution


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