2.1.5 Redox

Question 1

What is an oxidation number ?

Answer 1

the total number of electrons that an atom either** gains or loses** in order to form a chemical bond with another atom.
It is a + or - sign followed by a number
(total number of electrons lost or gained by an atom in a compound)

Question 2

Rule for oxidation number in elements

Answer 2

Oxidation **number of 0 **
(H2 = 0, Ca = 0)

Question 3

Rule for oxidation numbers in monoatomic ions

Answer 3

Oxidation number is the same as the ionic charge
(Zn 2+ = +2)

Question 4

Rule for oxidation number in polyatomic ions

Answer 4

**Sum **of the individual oxidation numbers = overall charge on the ion

Question 5

Rule for oxidation number in a neutral compound

Answer 5

Sum of oxidation numbers = 0

Question 6

Oxidation number of fluorine (IN A COMPOUND)

Answer 6

-1

This is the most electronegative element

Question 7

Oxidation number of oxygen
(In a compound)

Answer 7

-2
-Bonded to flurorine = +2
-In a peroxide = -1

Question 8

Oxidation number of hydrogen
(In a compound)

Answer 8

+1
(Unless bonded to a metal - metal hydride- then it is -1)

This is because** hydrogen only has one electron** so it can either lose the electron to a non metal and gain a positive charge, or** it can gain an electron** from a metal and gain a negative charge

Question 9

Oxidation number of chlorine
(In a compound)

Answer 9

-1

Question 10

What do roman numerals show ?

Answer 10

They show the oxidation number of variable elements

Question 11

Define redox reaction

Answer 11

A reaction involving reduction and oxidation
(They always occur together)

Question 12

Define oxidation and reduction in terms of electrons

Answer 12

Oxidation = loss of electrons
Reduction = gain of electrons
(Total electrons lose = Total electrons gained)

OILRIG (Oxidation is loss, reduction is gain)

Question 13

Define oxidation and reduction in terms of oxidation number

Answer 13

Oxidation = increased oxidation number
Reduction = decreased oxidation number
(Total increase in oxidation no. = Total decrease in oxidation no. - They must balance)

Question 14

In a redox reaction, what type of elements typically gain electrons, and which donate electrons ?

Answer 14

Metals = lose electrons (to become positive ions)
Non-metals = gain electrons (to become negative ions)