Take about 2 ml. of dilute NaOH solution in a test tube and add two drops of phenolphthalein solution.

What is the colour of the solution?

Add dilute HCL solution to the above solution drop by drop,

Is there any colour change for the reaction mixture?

Why did the colour of phenolphthalein change after the addition of an acid?

Now add a few drops of NaOH to the above mixture.

Does the pink colour of phenolphthalein reappear?

* Why do you think this is happened?


Meritnation experts please help me with this question...

Dear Student,

Phenolphthalein is basic indicator which remain colourless in acidic and neutral solution and turns pink or magenta in basic solution. 

(i) When few drops of phenolphthalein is added to 2 ml dilute sodium hydroxide, the solution turns deep pink as NaOH is a strong base. 

(ii) Yes, if dilute HCl is added to the solution then the colour of the solution get fades and if we keep on adding HCl, the solution becomes colourless.

(iII) The colour change occur on addition of acid as HCl being a strong acid will neutralize NaOH. 

(iv) If few drops of NaOH is added again to the same solution, the solution become basic and the pink colour of the phenolphthalein reappears. So, yes the pink colour of phenolphthalein reappears 

Regards

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