2.1.5: Redox

Question 1

What is an oxidation number?

Answer 1

The number of electrons an atom uses to bond with any other atom

Question 2

What is the oxidation number of an uncombined element such as C, H, O2?

Answer 2

0

Question 3

What is the oxidation number of combined oxygen such as in H2O?

Answer 3

-2

Question 4

What is the oxidation number of oxygen in peroxides?

Answer 4

-1

Question 5

What is the oxidation number of combined hydrogen such as in NH3, H2S?

Answer 5

+1

Question 6

What is the oxidation number of hydrogen in metal hydrides such as LiH?

Answer 6

-1

Question 7

What is the oxidation number of a simple ion?

Answer 7

Charge on the ion
E.g Na+
→ +1 ; Cl-
→ -1

Question 8

What is the oxidation number of combined fluorine such as in NaF, CaF2?

Answer 8

-1

Question 9

What is the oxidation number of Fe in iron (III) chloride?

Answer 9

+3

Question 10

What are oxyanions?

Answer 10

Negative ions that have an element along with oxygen

Question 11

What is the oxidation number of S in SO4 2-?

Answer 11

+6
Because, combined oxygen has an oxidation number of -2.
4 x -2 = -8.
The charge on the compound is -2. Sum of oxidation numbers must equal -2
So, -2 -(-8) = +6

Question 12

Define oxidation in terms of electron transfer and oxidation number

Answer 12

Oxidation is
● Loss of electrons
● An increase in oxidation number

Question 13

What is a redox reaction?

Answer 13

A reaction in which both oxidation and

reduction takes place

Question 14

What is the oxidation number of a metal?

Answer 14

0, because it is an uncombined element