To tackle this question, let’s break down the information provided and identify the compounds step by step. The solid ‘A’ you’re referring to is likely a form of copper(II) oxide, which is a blackish-brown solid. When it reacts with alkali metal hydroxides in the presence of air, it forms a dark green compound ‘B’, which is probably a copper(II) hydroxide complex. Upon electrolytic oxidation in an alkaline medium, this compound transforms into a dark purple compound ‘C’, which is likely to be a copper(II) complex such as copper(II) oxide or a related species. Let’s delve into the reactions involved.
Identifying the Compounds
Compound A: Copper(II) Oxide
Compound A is copper(II) oxide (CuO), a blackish-brown solid. It is known for its ability to react with bases.
Compound B: Copper(II) Hydroxide Complex
When copper(II) oxide reacts with an alkali metal hydroxide (like sodium hydroxide, NaOH) in the presence of air, it forms a dark green compound, which can be represented as:
- CuO + 2 NaOH + H2O → Cu(OH)2 + Na2O
In this reaction, the copper(II) oxide reacts with sodium hydroxide and water to form copper(II) hydroxide, which can appear as a dark green precipitate.
Compound C: Copper(II) Complex
Upon electrolytic oxidation of the copper(II) hydroxide in an alkaline medium, we can produce a dark purple compound. This can be represented as:
- Cu(OH)2 + 2 e⁻ → Cu + 2 OH⁻
- Cu + 2 OH⁻ + O2 → Cu(OH)2 (in presence of air)
However, during the oxidation process, the copper can form various complexes, and one of the common products is a copper(II) complex that appears dark purple, such as copper(II) tetraamine complex.
Summary of Reactions
To summarize, the sequence of reactions can be outlined as follows:
- CuO + 2 NaOH + H2O → Cu(OH)2 (dark green compound B)
- Electrolytic oxidation: Cu(OH)2 → Cu complex (dark purple compound C)
In conclusion, the compounds identified are:
- A: Copper(II) oxide (CuO)
- B: Copper(II) hydroxide (Cu(OH)2)
- C: Copper(II) complex (dark purple)
This sequence illustrates the transformation of copper compounds through chemical reactions, showcasing the fascinating interplay between oxidation states and complex formation in inorganic chemistry.
