Oxidation Numbers and Redox Reactions

Front

What is an oxidation number?

Back

The oxidation number is a value that represents the total number of electrons an atom either gains or loses when it forms a compound.

Front

How do you determine the oxidation number of an element in a compound?

Back

The oxidation number can be determined by following a set of rules, including the oxidation state of elements in their elemental form is zero, and the sum of oxidation numbers in a neutral compound is zero.

Front

What does an increase in oxidation number indicate?

Back

An increase in oxidation number indicates that the element is being oxidized, meaning it loses electrons.

Front

What does a decrease in oxidation number indicate?

Back

A decrease in oxidation number indicates that the element is being reduced, meaning it gains electrons.

Front

In the reaction 2Ca + O2 → 2CaO, what is the oxidation number change for calcium?

Back

Calcium changes from 0 in elemental form to +2 in CaO.

Front

In the reaction Na + PbCl2 → Pb + NaCl, which element is oxidized?

Back

Sodium (Na) is oxidized as it goes from 0 to +1.

Front

What is the oxidation state of oxygen in most compounds?

Back

The oxidation state of oxygen is usually -2 in most compounds.

Front

What is the oxidation state of hydrogen in compounds?

Back

The oxidation state of hydrogen is usually +1 when bonded to nonmetals and -1 when bonded to metals.

Front

What is a redox reaction?

Back

A redox reaction is a chemical reaction that involves the transfer of electrons between two species, resulting in changes in oxidation states.

Front

What is the oxidation state of lead (Pb) in PbO?

Back

The oxidation state of lead in PbO is +2.