Question

Copper corrodes to cuprous oxide, \(\mathrm{Cu}_{2} \mathrm{O},\) or cupric oxide, \(\mathrm{CuO},\) depending on environmental conditions. (a) What is the oxidation state of copper in cuprous oxide? (b) What is the oxidation state of copper in cupric oxide? (c) Copper peroxide is another oxidation product of elemental copper. Suggest a formula for copper peroxide based on its name. (d) Copper(III) oxide is another unusual oxidation product of elemental copper. Suggest a chemical formula for copper(II) oxide.

Short answer

(a) The oxidation state of copper in cuprous oxide is +1. (b) The oxidation state of copper in cupric oxide is +2. (c) The chemical formula for copper peroxide is CuO₂. (d) The chemical formula for copper(II) oxide is CuO.

Step-by-step solution

Find oxidation state of copper in cuprous oxide

Cuprous oxide has a chemical formula of \(\mathrm{Cu}_{2}\mathrm{O}\). To find the oxidation state, we must look at the oxygen atom's oxidation state, which is always -2. Since the total charge in any compound is neutral (zero), we can calculate the oxidation state of the copper atom.

Write the equation and solve for oxidation state of copper

Let x be the oxidation state of copper in cuprous oxide. The equation for calculating oxidation state is: \(2x + (-2) = 0 \) Solve for x: \(2x = 2 \) \(x = +1 \) The oxidation state of copper in cuprous oxide is +1.

Find oxidation state of copper in cupric oxide

Cupric oxide has a chemical formula of \(\mathrm{CuO}\). Similar to Step 1, we look at the oxygen atom's oxidation state, which is always -2.

Write the equation and solve for oxidation state of copper

The equation for calculating oxidation state for cupric oxide is: \(x + (-2) = 0 \) Solve for x: \(x = +2 \) The oxidation state of copper in cupric oxide is +2.

Suggest a formula for copper peroxide

Copper peroxide is a compound containing copper and peroxide ions (O2²⁻). Since copper's oxidation state stays constant, we can assume it is +2. A balanced chemical formula will have equal positive and negative charges. Cu²⁺ + (O2²⁻) → Cu(O2) or CuO₂ Copper peroxide's chemical formula is CuO₂.

Suggest a formula for copper(II) oxide

Copper(II) oxide implies that copper has an oxidation state of +2. Oxygen has an oxidation state of -2. Writing the balanced chemical formula: Cu²⁺ + O²⁻ → CuO The chemical formula for copper(II) oxide is CuO.

Key concepts

Cuprous Oxide

Cuprous oxide is a reddish solid with the chemical formula \( \mathrm{Cu}_2\mathrm{O} \). It is one of the principal oxides of copper. The oxidation state of copper in cuprous oxide is +1, which indicates that each copper atom loses one electron. When we reason through the stoichiometry of the formula, considering oxygen's consistent -2 oxidation state, the two copper atoms collectively compensate for the charge brought by the single oxygen atom.

To simplify, let's recall that the sum of oxidation states in a neutral compound is zero. Therefore, if we have two copper atoms at an oxidation state of +1 each (summing up to +2), they perfectly balance out the -2 charge from the oxygen, thus maintaining charge neutrality. This balance is essential to understanding the electrochemistry involved in processes where cuprous oxide might be a reactant or a product. Cuprous oxide is commonly found in various applications such as antifouling agents for marine paints and as an agricultural fungicide.

Cupric Oxide

Moving on to cupric oxide, which appears as a black or dark brown powdery solid, and is most commonly represented by the formula \( \mathrm{CuO} \). Unlike cuprous oxide, the copper in cupric oxide exhibits an oxidation state of +2. This means that in the compound, each copper atom has lost two electrons.

Using the same rule of thumb, with oxygen holding an oxidation state of -2, a single copper atom balances the charge of one oxygen atom, maintaining the compound's overall neutrality. This +2 oxidation state of copper is more common than the +1 state found in cuprous oxide. Cupric oxide is utilized in various areas such as catalysis, in ceramics to produce glazes, as well as in the production of copper salts. It's also a crucial component in the manufacture of dry cell batteries.

Copper Peroxide

Copper peroxide is an interesting compound conceptualized based on its name to have a peroxide component. Peroxides typically contain the \( \mathrm{O}_2^{2-} \) group, which is known for its -2 charge as a whole. Suggesting a formula for copper peroxide would involve pairing copper in its +2 oxidation state, \( \mathrm{Cu}^{2+} \), with the peroxide anion to maintain charge balance.

The speculated chemical formula of copper peroxide is therefore \( \mathrm{CuO}_2 \). This formula stems from the reasoning that the copper with a +2 charge neutralizes the charge from the two oxygen atoms which together have a -2 charge. Though copper peroxide is not commonly encountered and is less stable than the other copper oxides, it comes up in discussions surrounding the copper corrosion process and may have niche applications in organic synthesis discussions.

Copper(II) Oxide

Copper(II) oxide, also simply known as cupric oxide, holds significant importance in the realm of copper compounds. As indicated earlier, its chemical formula is \( \mathrm{CuO} \), and it presents as a solid with a dark brown to black coloration. The (II) in the name stands for the oxidation state of the copper ion, which is +2, and this is clearly reflected in the compound's stoichiometry.

This compound is the outcome of the more common oxidation state of copper (+2) combining with oxygen, which has an oxidation state of -2. Copper(II) oxide has a vast array of uses, including acting as a pigment in ceramics and glassmaking, being a precursor for other copper-containing products, and playing a role in electronics and solar cells. Understanding its chemical structure and properties is paramount for students tackling topics in inorganic chemistry and material science.