If a substance gives hydroxide ions in water, what effect will its solution show on an indicator?
Answer and explanation
Correct answer: It will turn red litmus blue
The governing concept is the definition of a base in aqueous solution: it produces hydroxide ions or increases their concentration. Basic solutions turn red litmus paper blue. They generally turn phenolphthalein pink and methyl orange yellow, so the statements saying these indicators are always colourless or red are incorrect. Blue litmus is associated with acids turning it red, not with bases. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
It will turn red litmus blue
Why is this the correct answer?
The governing concept is the definition of a base in aqueous solution: it produces hydroxide ions or increases their concentration. Basic solutions turn red litmus paper blue. They generally turn phenolphthalein pink and methyl orange yellow, so the statements saying these indicators are always colourless or red are incorrect. Blue litmus is associated with acids turning it red, not with bases. Therefore 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.
