If a solution turns red indicator paper blue and phenolphthalein pink, which pH is most likely?
Answer and explanation
Correct answer: 11
Turning red indicator paper blue shows that the solution is basic rather than acidic or neutral. Phenolphthalein becoming pink supports the same conclusion because it is pink in a sufficiently alkaline medium. Of the listed values, pH 11 is clearly basic, whereas pH 7 is neutral and pH 3 or 1 are acidic. Therefore option A is the only value consistent with both indicator observations.
Frequently asked questions
What is the correct answer to this question?
11
Why is this the correct answer?
Turning red indicator paper blue shows that the solution is basic rather than acidic or neutral. Phenolphthalein becoming pink supports the same conclusion because it is pink in a sufficiently alkaline medium. Of the listed values, pH 11 is clearly basic, whereas pH 7 is neutral and pH 3 or 1 are acidic. Therefore option A is the only value consistent with both indicator observations.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
