A colourless solution turns blue indicator paper red but produces no bubbles with carbonate. Which conclusion is most correct?
Answer and explanation
Correct answer: The solution may be acidic, but the test conditions or carbonate may be unsuitable.
A blue indicator paper turning red is evidence that the solution is acidic. Many acids react with carbonates to release carbon dioxide, so bubbling would normally be expected when the reagent and conditions are suitable. However, no bubbles can result from an unsuitable or insufficient carbonate, low acid concentration, poor contact, or an experimental fault. Thus the cautious conclusion in A is best; the observation does not prove that the solution is basic, neutral, or only sugar.
Frequently asked questions
What is the correct answer to this question?
The solution may be acidic, but the test conditions or carbonate may be unsuitable.
Why is this the correct answer?
A blue indicator paper turning red is evidence that the solution is acidic. Many acids react with carbonates to release carbon dioxide, so bubbling would normally be expected when the reagent and conditions are suitable. However, no bubbles can result from an unsuitable or insufficient carbonate, low acid concentration, poor contact, or an experimental fault. Thus the cautious conclusion in A is best; the observation does not prove that the solution is basic, neutral, or only sugar.
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.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
