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 sit he 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 combined 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

When an element has more than one stable oxidation number, how is it indicated

Answer 9

Written as a Roman numeral

Question 10

What is the oxidation number of Fe in Iron (lll) chloride?

Answer 10

+3

Question 11

What are oxyanions?

Answer 11

Negative ions that have an element along with oxygen

Question 12

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

Answer 12

+6

Because, combined oxygen has an oxidation number of -2

4 x -2 = -8

The chrage on the compound is -2. Sum of oxidation numbers must equal -2

-2 -(-8) = +6

Question 13

Define oxidation in terms of electron transfer and oxidation number

Answer 13

Oxidation is
loss of electrons
an increase in oxidation number

Question 14

Define reduction in terms of electron transfer and oxidation number

Answer 14

Reduction is
Gain of electrons
A decrease in oxidation number

Question 15

What is a redox reaction?

Answer 15

A reaction in which both oxidation and reduction takes place

Question 16

What is the oxidation number of a metal?

Answer 16

0

because it is an uncombined element