If a solution showing blue colour with universal indicator turns green after adding acid, what happened?
Answer and explanation
Correct answer: The solution changed from basic to nearly neutral.
Universal indicator gives different colours over a pH range: blue generally indicates a basic solution, while green indicates a value close to neutral. When acid is added, hydrogen ions react with hydroxide ions in the basic solution, reducing its alkalinity. If the colour becomes green, the mixture has reached approximately neutral pH. It has not become more basic, and the observation does not prove that it is a strong acid.
Frequently asked questions
What is the correct answer to this question?
The solution changed from basic to nearly neutral.
Why is this the correct answer?
Universal indicator gives different colours over a pH range: blue generally indicates a basic solution, while green indicates a value close to neutral. When acid is added, hydrogen ions react with hydroxide ions in the basic solution, reducing its alkalinity. If the colour becomes green, the mixture has reached approximately neutral pH. It has not become more basic, and the observation does not prove that it is a strong acid.
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.
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