C7. Oxidation, Reduction, and Redox Reactions

Question 1

What is the oxidation number of uncombined elements?

Answer 1

Always 0

Question 2

What is the oxidation number of ions?

Answer 2

Same as charge on ion

Question 3

What is the oxidation number of group 1?

Answer 3

Always +1

Question 4

What is the oxidation number of group 2?

Answer 4

Always +2

Question 5

What is the oxidation number of aluminium?

Answer 5

Always +3

Question 6

What is the oxidation number of hydrogen?

Answer 6

+1 (In hydrides, metal bonded with hydrogen, -1)

Question 7

What is the oxidation number of chlorine?

Answer 7

-1 (When bonded with F or O, positive value)

Question 8

What is the oxidation number of fluorine?

Answer 8

Always -1

Question 9

What is the oxidation number of Oxygen?

Answer 9

-2 (In peroxides -1, In OF2 +2)

Question 10

What is oxidation?

Answer 10

Loss of electrons; increase in oxidation number

Question 11

What is reduction?

Answer 11

Addition of electrons; decrease in oxidation number

Question 12

What do redox half equations show?

Answer 12

Reduction & oxidation stages in 2 equations; half equations must have electrons

Question 13

What are the rules for balancing redox half equations?

Answer 13

1. Note species before and after reaction
2. Balance any atoms except O & H
3. Balance O with H2O
4. Balance H with H+ ions
5. Balances charges with electrons

Question 14

What does a combined half equation show?

Answer 14

Full ionic equation, no electrons, reduction and oxidation