What Are the Observations When Lead Nitrate Is Heated?

When Pb(NO₃)₂ (lead nitrate, a white crystalline solid) is heated in a test tube:

1. Brown/reddish-brown fumes are observed — these are nitrogen dioxide (NO₂) gas.
2. A cracking sound may be heard initially (due to rapid decomposition).
3. A yellow solid remains — lead oxide (PbO), also called litharge.
4. A glowing splint held near the mouth of the test tube relights — oxygen (O₂) is produced.
5. The white solid gradually turns yellow as it decomposes.

Equation: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂

Word equation: Lead nitrate → Lead(II) oxide + Nitrogen dioxide + Oxygen

1. Lead(II) Oxide (PbO): • Bright yellow powder (called litharge) • Basic oxide — reacts with acids to form lead salts • PbO + 2HNO₃ → Pb(NO₃)₂ + H₂O • Used in making lead glass and lead-acid batteries

2. Nitrogen Dioxide (NO₂): • Brown/reddish-brown gas • Pungent, choking odour • Toxic gas • Acidic oxide: 3NO₂ + H₂O → 2HNO₃ + NO

3. Oxygen (O₂): • Colourless, odourless gas • Supports combustion — relights a glowing splint

Note on PbO colour: • PbO is yellow at room temperature • When heated strongly, it may also form Pb₃O₄ (red lead / minium) or PbO₂ under specific conditions

The heating of lead nitrate is a standard CBSE Class 10 chemistry experiment that demonstrates:

1. Thermal decomposition — one compound breaks into multiple products.
2. Colour change — white Pb(NO₃)₂ → yellow PbO.
3. Gas evolution — brown NO₂ and colourless O₂.

Comparison with zinc nitrate: Zn(NO₃)₂ heated: 2Zn(NO₃)₂ → 2ZnO + 4NO₂ + O₂ (same type) Both Zn and Pb are moderately reactive metals, hence both give metal oxide + NO₂ + O₂.

Key difference: • ZnO is white (turns yellow when hot, back to white when cool) • PbO is yellow (permanent colour)

Activity series position of Pb: • Below hydrogen, above Cu • Moderately reactive — gives metal oxide on heating its nitrate