Stage 1: Lower Temperature (around 170°C)
* Reaction: Cu(NO₃)₂(s) → CuO(s) + 2NO₂(g) + ½O₂(g)
* Explanation: The copper(II) nitrate decomposes into copper(II) oxide (CuO), nitrogen dioxide gas (NO₂), and oxygen gas (O₂). This reaction is exothermic, meaning it releases heat.
Stage 2: Higher Temperature (above 300°C)
* Reaction: CuO(s) + NO₂(g) → Cu(s) + ½O₂(g) + NO₂(g)
* Explanation: At higher temperatures, the copper(II) oxide further decomposes into copper metal (Cu), oxygen gas, and nitrogen dioxide. This reaction is also exothermic.
Overall, the final products of heating copper(II) nitrate are:
* Copper metal (Cu): This is a reddish-brown solid.
* Nitrogen dioxide (NO₂): This is a reddish-brown gas with a pungent odor.
* Oxygen gas (O₂): This is a colorless and odorless gas.
Observations:
* Color change: Initially, the copper(II) nitrate is blue. As it decomposes, the solid changes color to black (CuO) and then eventually to reddish-brown (Cu).
* Gas evolution: The release of nitrogen dioxide and oxygen gas is evident as brown fumes are seen coming off the heated sample.
Safety:
* The decomposition of copper(II) nitrate produces toxic gases. It's crucial to perform this experiment in a well-ventilated area.
* Nitrogen dioxide is a respiratory irritant. It's essential to avoid inhaling the fumes.
In summary, heating copper(II) nitrate results in its decomposition into copper metal, nitrogen dioxide, and oxygen gas, accompanied by a color change and the release of brown fumes.
