If a solution turns red litmus blue and phenolphthalein pink, what is its likely pH?
Answer and explanation
Correct answer: 11
Red litmus turning blue demonstrates that the solution is basic, while phenolphthalein becoming pink confirms an alkaline medium. A pH greater than 7 is therefore required. Of the choices, pH 11 clearly represents a basic solution; pH 2 and 5 are acidic, and pH 7 is neutral, so they cannot explain both indicator changes.
Frequently asked questions
What is the correct answer to this question?
11
Why is this the correct answer?
Red litmus turning blue demonstrates that the solution is basic, while phenolphthalein becoming pink confirms an alkaline medium. A pH greater than 7 is therefore required. Of the choices, pH 11 clearly represents a basic solution; pH 2 and 5 are acidic, and pH 7 is neutral, so they cannot explain both indicator changes.
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.
