The equation 4HNO3 + Cu2S -> 2NO2 + 2H2O + 2Cu(NO3)2 + S

  1. Detailed information about the Chemical Equation:
    The chemical reaction between 4 moles of nitric acid (HNO3) and 1 mole of copper sulfide (Cu2S) produces 2 moles of nitrogen dioxide (NO2), 2 moles of water (H2O), 2 moles of copper(II) nitrate (Cu(NO3)2), and 1 mole of sulfur (S).

  2. Reaction conditions:

    • Acidic environment.
    • Room temperature or slightly higher.

  3. Reaction process:

    • The reaction occurs via a rearrangement mechanism.
    • First, nitric acid attacks copper sulfide to form copper nitrate.
    • At this point, some nitric acid is reduced to nitrogen dioxide.
    • Then, copper nitrate continues to react with nitric acid to produce copper(II) nitrate, water, and sulfur.

  4. Occurring phenomena:

    • During the reaction, the black solid of copper sulfide disappears.
    • Brown gas (nitrogen dioxide) is released.
    • At the end of the reaction, the obtained solution turns blue due to the presence of copper(II) nitrate.

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