Methyl orange turns yellow and phenolphthalein turns pink in a solution. What is the nature of the solution?
Answer and explanation
Correct answer: Basic
Indicator colour ranges provide the governing evidence. Methyl orange is yellow in a neutral or alkaline medium and red in a sufficiently acidic medium. Phenolphthalein is pink in an alkaline medium and colourless in acidic or near-neutral conditions. Seeing both yellow methyl orange and pink phenolphthalein therefore indicates that the solution is basic, sufficiently above the phenolphthalein transition range. An acidic solution would make methyl orange red and phenolphthalein colourless. Hence option A is correct.
Frequently asked questions
What is the correct answer to this question?
Basic
Why is this the correct answer?
Indicator colour ranges provide the governing evidence. Methyl orange is yellow in a neutral or alkaline medium and red in a sufficiently acidic medium. Phenolphthalein is pink in an alkaline medium and colourless in acidic or near-neutral conditions. Seeing both yellow methyl orange and pink phenolphthalein therefore indicates that the solution is basic, sufficiently above the phenolphthalein transition range. An acidic solution would make methyl orange red and phenolphthalein colourless. Hence option A is correct.
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.
