This is an **oxidation-reduction** (redox) reaction:

**Cu**0 - *2* **e**- → **Cu**II *(oxidation)*

**O**0 + *2* **e**- → **O**-II *(reduction)*

*Cu* is a **reducing** agent, *O* is an **oxidizing** agent

## Word equation

**copper + oxygen → cupric oxide **

## Input interpretation

**Cu + ****O****2**** → Cuo**

** copper oxygen cupric oxide**

## Balanced equation

Balance the chemical equation algebraically:

**Cu + ****O****2**** → CuO**

Add stoichiometric coefficients, c, to the reactants and products:

c1** Cu + **c2 **O****2**** → **c3** Cuo**

Set the number of atoms in the reactants equal to the number of atoms in the products for **Cu** and **O**:

**Cu: **c1**=**c3

**O: 2**c2**=**c3

Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c2 = 1 and solve the system of equations for the remaining coefficients:

c1**=2**

c2**=1 **c3**=2**

Substitute the coefficients into the chemical reaction to obtain the balanced

equation:

**Answer:**

**2 Cu + ****O****2**** → 2CuO**