Suppose you have four test tubes labelled as A, .B, C and T) A contains plain water, B contains solution of an alkali, C* contains solution of an acid, and D contains solution of sodium chloride. Which one of these solutions will turn phenolphthalein solu

examrobotsa's picture

Submitted by examrobotsa on

Q: 45 (NDA-I/2016)
Suppose you have four test tubes labelled as ‘A’, .‘B’, ‘C’ and T) ‘A’ contains plain water, ‘B’ contains solution of an alkali, ‘C* contains solution of an acid, and ‘D’ contains solution of sodium chloride.
Which one of these solutions will turn phenolphthalein solution pink ?

question_subject: 

Science

question_exam: 

NDA-I

stats: 

0,10,17,3,10,13,1

keywords: 

{'test tubes': [0, 0, 0, 1], 'phenolphthalein solution': [0, 0, 0, 1], 'solutions': [0, 0, 2, 3], 'acid': [2, 1, 4, 16], 'solution': [2, 0, 7, 14], 'sodium chloride': [1, 0, 0, 1], 'plain water': [0, 0, 1, 1]}

Out of the given options, the solution that will turn phenolphthalein solution pink is option 2, Solution `B`.

To dissect each option:

Option 1, Solution `A` is plain water. Plain water does not have any acidic or basic properties to cause a color change in phenolphthalein solution. Therefore, it would not turn pink.

Option 2, Solution `B` is a solution of an alkali. Alkalis are substances that have a higher concentration of hydroxide ions (OH-) and can react with phenolphthalein solution to turn it pink.

Option 3, Solution `C` is a solution of an acid. Acids have a higher concentration of hydrogen ions (H+) and cannot react with phenolphthalein solution to turn it pink.

Option 4, Solution `D` is a solution of sodium chloride. Sodium chloride is a neutral substance and does not have any acidic or basic properties to react with phenolphthalein solution. Therefore, it would not turn pink.

In conclusion, option 2, Solution `B`, is the correct answer as it is the only solution containing an alkali that can react with phenolphthalein solution to turn it pink.