Oxidation States and Half Reactions

Front

What is an oxidation state?

Back

An oxidation state (or oxidation number) is a measure of the degree of oxidation of an atom in a substance, indicating the number of electrons lost or gained.

Front

What does it mean for an element to be oxidized?

Back

An element is oxidized when it loses electrons, resulting in an increase in its oxidation state.

Front

What does it mean for an element to be reduced?

Back

An element is reduced when it gains electrons, resulting in a decrease in its oxidation state.

Front

What is a half-reaction?

Back

A half-reaction is an equation that shows either the oxidation or reduction process separately, indicating the transfer of electrons.

Front

In a redox reaction, what happens to the total charge?

Back

The total charge remains the same; the number of electrons lost in oxidation equals the number of electrons gained in reduction.

Front

What is the oxidation state of an element in its elemental form?

Back

The oxidation state of an element in its elemental form is always zero.

Front

How do you determine the oxidation state of oxygen in compounds?

Back

Oxygen typically has an oxidation state of -2 in compounds, except in peroxides where it is -1.

Front

What is the oxidation state of chlorine in Cl2?

Back

The oxidation state of chlorine in Cl2 is 0.

Front

What happens to the oxidation state of calcium in the reaction 2Ca + O2 -> 2CaO?

Back

The oxidation state of calcium changes from 0 to +2, indicating it is oxidized.

Front

What is the oxidation state of sodium in NaCl?

Back

The oxidation state of sodium in NaCl is +1.