If gas evolves in an unknown reaction but colour does not change what is the most careful conclusion?
Answer and explanation
Correct answer: Gas formation may indicate a chemical reaction; other observations should also be checked for confirmation
A colour change can be a sign of a chemical reaction, but it is not necessary in every chemical reaction. Formation of a gas may suggest that a new substance has formed, so it can indicate a chemical reaction. However, bubbles alone are not conclusive because a physical process such as boiling can also produce bubbles. Check additional observations, such as temperature change, precipitate, odour, or the identity of the gas. Exam tip: Do not treat a single observation as conclusive evidence.
Frequently asked questions
What is the correct answer to this question?
Gas formation may indicate a chemical reaction; other observations should also be checked for confirmation
Why is this the correct answer?
A colour change can be a sign of a chemical reaction, but it is not necessary in every chemical reaction. Formation of a gas may suggest that a new substance has formed, so it can indicate a chemical reaction. However, bubbles alone are not conclusive because a physical process such as boiling can also produce bubbles. Check additional observations, such as temperature change, precipitate, odour, or the identity of the gas. Exam tip: Do not treat a single observation as conclusive evidence.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
