Copper(II) Sulfate Redox Reactions

Demonstration of redox (oxidation-reduction) reactions using copper(II) sulfate (cupric sulfate).
Copper compounds are favored due to their bluish-green color.

Copper Chloride: Greenish color.
Copper Carbonate: Greenish powder (solid).
Copper Acetate: The presenter's favorite.
Copper(II) Sulfate: Dark blue crystal when concentrated; light greenish-blue in less concentrated solutions.

A solution of copper(II) sulfate is used.
Sodium chloride (table salt) is added to increase the electrolytic nature of the solution to facilitate electron flow in the redox reaction.
The reaction can occur without sodium chloride, but it proceeds more slowly and with less impressive results.

Copper(II) sulfate solution is divided into four shot glasses.
Four different metals are added to each glass: aluminum, zinc, iron, and copper.

Aluminum: Coated with a reddish-brown solid.
Zinc: Coated with a reddish-brown solid, with the zinc itself breaking apart.
Iron: Coated with a brownish-red coating (rust).
Copper: Appears relatively unchanged.

Remaining copper(II) sulfate is poured into a beaker.
A large piece of zinc (from a six-volt lantern battery electrode) is submerged in the copper(II) sulfate solution.
The copper coats the zinc, and copper accumulates at the bottom of the beaker and floats on top of the zinc casing.

All reactions are oxidation-reduction (redox) reactions.
Copper ion (cupric ion) in copper(II) sulfate is in solution as an electrolyte.
When the copper ion interacts with a more active metal, it is reduced to solid copper (reddish-brown solid).
As the cupric ion ($\Cu^{2+}) is reduced to solid copper ($\Cu), the blue color of the solution fades; the solution becomes almost clear as the copper cation is converted to solid copper.
Active metals (zinc, aluminum, and iron) are oxidized; they lose electrons and become metallic ions.

Reduction: Cupric ion ( $Cu^{2+}$ ) gains two electrons ($\2e^− $) to become solid copper:$ Cu^{2+} + 2e^− → Cu.
Oxidation: Active metals lose electrons to become ions.
- For example, zinc ($\Zn) loses two electrons to become zinc ion ( $Zn^{2+}$ ): $Zn → Zn^{2+} + 2e^−$ .

No reaction occurs when copper metal is placed in copper(II) sulfate because copper is the same in terms of reactivity as copper.
Copper is one of the least active metals.
Metals less active than copper include gold, platinum, and silver.

The video is the last one before Christmas and New Year's.
A break is announced, with a return in the next year with Painting of the Week and the conclusion of the Garden of Earthly Delights analysis.