All High School Chemistry Resources
Example Questions
Example Question #1 : Help With Oxidation Reduction Reactions
What is the oxidation number of sulfur in the given compound?
Use the rules for assigning oxidation numbers. We know that the sum of oxidation numbers of all atoms present in the compound must equal zero because the compound is neutral.
The oxidation number of hydrogen is except in compounds with less electronegative elements (which is not the case here). Because there are two hydrogens, the overall oxidation is .
The oxidation number of oxygen is always . Multiply that by the total number of oxygens to get .
From here, simple math tells us that the oxidation number of sulfur must be to make the total oxidation state equal to zero.
Example Question #2 : Help With Oxidation Reduction Reactions
Which of the following describes a high energy, exothermic redox reaction that produces carbon dioxide and water?
Acid-base
Decomposition
Boiling
Combustion
Nuclear
Combustion
A combustion reaction is characterized as an oxidation-reduction reaction because the oxidation number of the reactants changes, and oxygen is used to burn a fuel molecule. Carbon dioxide is often produced as a product. The following is an example of a combustion reaction:
Example Question #2 : Help With Oxidation Reduction Reactions
Which of the following describes an oxidation-reduction reaction?
None of these
A reaction in which one species molecule is oxidized then reduced
A type of chemical reaction that always involves acids and bases
A type of reaction in which one reactant is broken down into two products
The transfer of electrons between species, and the subsequent changes in oxidation states
The transfer of electrons between species, and the subsequent changes in oxidation states
In an oxidation reaction, one species is oxidized (loses electrons). During a reduction reaction, one species is reduced (gains electrons). These transfers of electrons results in the change of oxidation states. One way to help you remember which reaction is which, is by using the mnemonic: OIL RIG - Oxidation Is Loss of electrons; Reduction Is Gain of electrons.