A solution gives red colour with universal indicator. After adding water the colour becomes yellow but not green. What is the correct conclusion?
Answer and explanation
Correct answer: The solution became less acidic but is still acidic
Universal-indicator colours represent approximate pH ranges. Red shows strong acidity, while yellow represents a less strongly acidic range. Adding water dilutes the solution and lowers the hydrogen-ion concentration per unit volume, so the colour shifts toward green, which represents neutrality. Because the result is yellow rather than green, neutralisation has not been reached; the solution remains acidic. Thus option A is correct, while B, C, and D are inconsistent with the observation.
Frequently asked questions
What is the correct answer to this question?
The solution became less acidic but is still acidic
Why is this the correct answer?
Universal-indicator colours represent approximate pH ranges. Red shows strong acidity, while yellow represents a less strongly acidic range. Adding water dilutes the solution and lowers the hydrogen-ion concentration per unit volume, so the colour shifts toward green, which represents neutrality. Because the result is yellow rather than green, neutralisation has not been reached; the solution remains acidic. Thus option A is correct, while B, C, and D are inconsistent with the observation.
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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