Question

Hands that have touched phenolphthalein powder will turn pink when dipped in:

• A. Water
• B. Carbonated water
• C. Soap solution
• D. Acetic acid solution

Answer 1

The correct option is C

Soap solution

Explanation for the correct option:

1. Indicators: Indicators are understood as the substance which changes color in an acidic or basic medium.
2. Some natural indicators are Litmus or red cabbage. Litmus changes from blue to red in acidic medium and red to blue in a basic medium.
3. Synthetic indicators would be phenolphthalein or methyl orange.
4. It is known that when the solution is basic, phenolphthalein gives a pink colour and when the solution is acidic, it remains colourless.
5. Here, among the given options, Soap solutions are slightly basic in nature because they are the salts of strong bases and weak acids. That's why they impart pink colour to the solution.

Explanation for the incorrect options:

1. Option (A) is incorrect as water is neither acidic or basic; it is neutral, so it will not turn phenolphthalein into pink.
2. Option (B) is incorrect as Carbonated water is acidic in nature and they do not impart color to the solution.
3. Option (D) is incorrect as Acetic acid solutions, being an acid it will not impart any color to the solution.

Therefore, option (C) is correct. i.e., Hands that have touched phenolphthalein powder will turn pink when dipped in Soap solution.