Final answer:
In reaction A) Cu+4HNO₃ ➔ Cu(NO₃)² +2H₂O+2NO₂, nitric acid acts as an oxidizing agent by oxidizing copper to copper(II) nitrate while being reduced to nitrogen dioxide.
Step-by-step explanation:
In the context of the provided reactions and the understanding of oxidizing agents, nitric acid (HNO₃) acts as an oxidizing agent in the reaction:
A) Cu+4HNO₃ ➔ Cu(NO₃)² +2H₂O+2NO₂
This reaction is an example of a redox process where copper (Cu) is oxidized by nitric acid. Copper initially in its metallic state (Cu) is oxidized to copper(II) nitrate (Cu(NO₃)²), while nitric acid is reduced to nitrogen dioxide (NO₂). Here, nitric acid donates oxygen to copper, causing copper to lose electrons, which is characteristic of an oxidizing agent.
The balanced chemical equations provided in the exercises demonstrate different aspects of redox chemistry, out of which the first example directly supports the identification of nitric acid as an oxidizing agent.
Exercise 20.2.1 mentions the extraction of copper from CuS using nitric acid to obtain sulfate and nitrogen monoxide, emphasizing the oxidative action of nitric acid. Contrary, the example of copper(II) oxide reacting with nitric acid to form copper(II) nitrate elucidates the use of nitric acid in producing a compound that serves to inhibit algae growth in swimming pools.
In summary, the role of nitric acid as an oxidizing agent is highlighted in these redox reactions, showcasing the importance of balancing chemical equations to understand electron transfer processes.