The brown gas on heating lead nitrate indicates the presence of which substance?
Answer and explanation
Correct answer: Nitrogen dioxide
On heating, lead nitrate undergoes thermal decomposition: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂. Nitrogen dioxide, NO₂, is a reddish-brown gas, so its characteristic colour identifies it as the gas observed. Oxygen is colourless, hydrogen is also colourless and is not produced in this decomposition, and carbon dioxide is not a product of lead nitrate decomposition. Therefore option C is correct.
Frequently asked questions
What is the correct answer to this question?
Nitrogen dioxide
Why is this the correct answer?
On heating, lead nitrate undergoes thermal decomposition: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂. Nitrogen dioxide, NO₂, is a reddish-brown gas, so its characteristic colour identifies it as the gas observed. Oxygen is colourless, hydrogen is also colourless and is not produced in this decomposition, and carbon dioxide is not a product of lead nitrate decomposition. Therefore option C is correct.
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.
