Aim : To test the change of colour in the reaction of an acid with a base.
Required Materials :
1) 2 ml of dilute NaOH (Sodium Hydroxide) solution.
2) Phenolphthalein indicator solution.
3) Dilute HCZ (Hydrochloric) solution.
1) Take about 2ml of dilute NaOH solution in a test tube.
2) Add two drops of phenolphthalein indicator solution.
Observation (i) :
1) It turns to red or pink colour.
2) It shows that NaOH is a base.
Experiment (1) : Add dilute HCZ solution to the above solution drop by drop. Observation (ii) : Pink colour disappears due to the reaction of NaOH (base) with HCZ (acid).
Experiment (2) : Now add one or two drops of NaOH to the above mixture. Observation (iii) : Pink colour reappears on adding NaOH.
Result: This reaction is called a neutralization reaction.