Drop a piece of copper foil into a test tube containing concentrated nitric acid in a fume cupboard. Describe what happens
When a piece of copper foil is dropped into a test tube containing concentrated nitric acid in a fume cupboard, the following reactions occur:
1. Initially, there might be no immediate visible reaction, but the copper foil starts to react with the nitric acid slowly.
2. As the copper foil reacts with the nitric acid, the solution in the test tube starts to turn blue or greenish-blue due to the formation of copper(II) nitrate. This occurs because nitric acid oxidizes the copper, converting it into its ionic form (Cu2+).
3. Simultaneously, brown-red fumes, which are nitrogen dioxide (NO2) gas, start to evolve from the test tube. Nitric acid acts as an oxidizing agent, oxidizing nitric oxide (NO) formed by the reaction of nitric acid with copper to nitrogen dioxide gas.
The overall chemical reaction can be represented as:
Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O
In this reaction, copper reacts with nitric acid to form copper(II) nitrate, nitrogen dioxide gas, and water.
It is important to conduct this reaction in a fume cupboard to ensure that any toxic fumes, such as nitrogen dioxide, are safely vented and do not pose a risk to the experimenter or the environment.
Summarize the above answers
When copper foil is dropped into concentrated nitric acid in a fume cupboard, it reacts slowly, forming a blue or greenish-blue solution due to the formation of copper(II) nitrate. Additionally, brown-red fumes of nitrogen dioxide gas are released. This reaction occurs because nitric acid oxidizes the copper, and the overall reaction can be represented as Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O. Conducting this reaction in a fume cupboard is necessary to ensure the safe venting of toxic fumes.
When a piece of copper foil is dropped into a test tube containing concentrated nitric acid in a fume cupboard, the following series of steps can be observed:
1. The copper foil initially appears shiny and metallic.
2. As soon as the copper foil comes into contact with the nitric acid, a reaction begins to take place.
3. The reaction between the copper and nitric acid produces nitrogen dioxide gas (NO2), which is reddish-brown in color and has a pungent odor. This gas is released into the fume cupboard. It is important to note that nitrogen dioxide is toxic and irritating, so working in a fume cupboard ensures safety.
4. The color of the copper foil starts to change, turning brownish initially and then progressing to a dark brown or black color.
5. As the reaction continues, the copper foil dissolves to form copper(II) nitrate, which is a soluble blue-green compound. This blue-green color can be observed in the solution formed.
6. The solution may effervesce due to the release of nitrogen dioxide gas, resulting in bubbling or fizzing.
7. Heating the test tube gently, if required, can accelerate the reaction between copper and nitric acid.
8. Eventually, the copper foil will completely dissolve, leaving behind a clear, blue-green solution of copper(II) nitrate.
It is essential to note that this reaction produces toxic fumes, so it should only be performed in a well-ventilated area, such as a fume cupboard, to ensure safety and the proper disposal of waste.