When lead nitrate is heated, it decomposes to form lead oxide, nitrogen dioxide, and oxygen. Which gas is brown in colour?
Answer and explanation
Correct answer: Nitrogen dioxide
This is a thermal decomposition reaction: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂. Nitrogen dioxide, NO₂, is a reddish-brown gas, so option B is correct. The oxygen released is colourless, nitrogen is also colourless, and nitric oxide is not the brown gas produced in this reaction. The observation of brown fumes is therefore a useful test for NO₂.
Frequently asked questions
What is the correct answer to this question?
Nitrogen dioxide
Why is this the correct answer?
This is a thermal decomposition reaction: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂. Nitrogen dioxide, NO₂, is a reddish-brown gas, so option B is correct. The oxygen released is colourless, nitrogen is also colourless, and nitric oxide is not the brown gas produced in this reaction. The observation of brown fumes is therefore a useful test for NO₂.
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.
