Question

While performing an activity in the lab students poured phenolphthalein indicator to four

different solutions taken in four different test tubes. A pink colour is observed in test tube

containing-




(a) HCl
(b)NaOH
(c) KCl
(d) NaCl​

Answer 1

Explanation:

Solution

The colour of the final mixture when added HCl to it

The colour (pink colour) will disappear.

the reaction between an acid and a base is known as neutralisation in this reaction and acid neutralizes the effect of acid and a base this reaction result in the formation of salt and water and energy in the form of heat is evolved.

Process:

fill half in test tube HCl and two drops of phenolphthalein to it start it continuously. next add Sodium Hydroxide till pink colour appears now add one drop of HCl the pink colour disappears so it is evident that when a solution is acidic it gives no colour this shows that neutralization reaction has occurred

Answer 2

A pink colour is observed in test tube containing- (b)NaOH

• Phenolphthalein is an acid base indicator. It is generally used to test for acid and base at the end of titration process. It remains colourless with acids and shows pink colour with bases.
• Among the following only NaOH is the only base. Hence, it would show pink colour. So, (b)NaOH is correct answer.
• HCl is an acid hence, phenolphthalein would remain colourless with it. So option a is incorrect.
• Both KCl and NaCl are salts. Hence, they are incorrect too.