Question

If you have been given a salt solution and an acidic solution, which
indicator would you prefer –methyl orange or phenolphthalein to test the two
colourless liquids. Give reason for your answer.

Answer 1

GiveN :-

• I have been given a salt solution and an acidic solution .
• I have been given phenolphthalein and methyl orange indicator .

To FinD :-

• Which indicator is more preferred.

SolutioN :-

Here I have been given a acidic and a neutral solution along with phenolphthalein and methyl orange indicator .

As we know that phenolphthalein changes to pink color in basic solutions and remains colourless is acidic and

basic solutions .

That is ,

$\sf:\implies \gray{ Base _{( in \ presence \ of \ phenolphthalein )} \to \pink{ Pink\ color } . }$

$\sf:\implies \gray{ Acid _{( in \ presence \ of \ phenolphthalein )} \to \pink{ No \ change } . }$

$\sf:\implies \gray{ Neural _{( in \ presence \ of \ phenolphthalein )} \to \pink{ No \ change} . }$

So If we use phenolphthalein we can't differentiate between a acid and a neutral solution. Whereas methyl orange changes to red color in presence of an acid and remains colourless in case of neutral solutions .

That is :-

$\sf:\implies \gray{ Base _{( in \ presence \ of \ Methyl \ orange )} \to \red{ Yellow \ color } . }$

$\sf:\implies \gray{ Acid _{( in \ presence \ of \ Methyl \ orange )} \to \red{ Red \ color} . }$

$\sf:\implies \gray{ Neural _{( in \ presence \ of \ Methyl\ orange )} \to \red{ No \ change} . }$

So methyl orange indicator should be used in place of Phenolphthalein .

$\boxed{\boxed{\textsf { Hence we should use \orange{ Methyl orange } in this case .}}}$