19.1.1 Reviewing Oxidation-Reduction Reactions

Question 1

Reviewing Oxidation-Reduction Reactions

Answer 1

• Oxidation-reduction reactions (redox reactions) are reactions in which electrons are transferred from one reactant to another.
• Redox reactions in which the changes are minor and easily controlled can be used to harness electricity.
• Redox reactions can be balanced by breaking the reaction into half-reactions.

Question 2

note

Answer 2

• In oxidation-reduction reactions (redox reactions), electrons are transferred from the reductant to the oxidant.
• The reductant loses electrons, and is oxidized itself.
• The oxidant gains electrons, and is reduced itself.
• Redox reactions involving a minimal rearrangement of atoms, a low kinetic barrier, and controlled changes (such as the oxidation of copper metal by silver ions) can be harnessed to produce electricity.
• Redox reactions involving a high kinetic barrier or a mixture of products (such as the oxidation of methane by oxygen) are harder to harness to produce electricity.
• Redox reactions can be balanced by breaking the reaction into half-reactions.
• This is done by identifying redox partners (Br 2 and Br – , for example), and writing a half-reaction for each.
• Each half-reaction is then balanced for oxygen atoms and hydrogen atoms using H 2 O and H + (in acid) or H 2 O and OH – (in base).
• Finally, the number of reactant electrons in the reduction half-reaction must be balanced with the number of product electrons.

Question 3

What is the oxidation number for chromium in K2Cr2O7 for the following reaction?

Answer 3

+6

Question 4

Which of the following is the balanced equation for the reaction between the permanganate ion and chloride ion in an acidic solution?

Answer 4

2MnO4- + 10Cl- + 16H+ -> 2Mn2+ + 5CL2 + 8H2O

Question 5

What is the common oxidation state for an alkaline earth metal?

Answer 5

+2

Question 6

What happens in all redox reactions?

Answer 6

There is a transfer of electrons.

Question 7

What is the common oxidation number for oxygen in a compound?

Answer 7

−2

Question 8

What is the oxidation number for nitrogen in Cu(NO3 )2 for the following reaction?

Answer 8

+5

Question 9

Which of the following is not true about reduction?

Answer 9

An increase in oxidation number occurs in the reduction half-reaction.

Question 10

Which of the following is necessary to balance a redox reaction?

Answer 10

Make the increase and decrease in oxidation numbers the same.

Question 11

What is an oxidation in a redox reaction?

Answer 11

An increase in oxidation number