Oxidation and Reduction

Question 0

Give an example of a chemical reaction involved in the transfer of electrons

Answer 0

Iron rusting

Question 1

I have lost an electron! Are you sure?

Answer 1

Yes I’m positive

Question 2

What is the name given to reactions involved in the transfer of electrons?

Answer 2

Oxidation and Reduction (Redox reactions)

Question 3

Use this equation to demonstrate the transfer of electrons between

Zn + Cu2

Answer 3

Zn + Cu2 -> Zn2 + Cu

Question 4

State whether oxidation or reduction is the loss of electrons, hence state which one is gain of electrons

Answer 4

Oxidation-Lost of electrons

Reduction-Gain of electrons

Question 5

State how many electrons are lost or gained by groups 1-7

Answer 5

Group 1= +1
Group 2= +2
Group 3= +3
Group 4= +/-4
Group 5= -3
Group 6= -2
Group 7= -1

Question 6

Uncombined elements have an oxidation number of zero. Account for the oxidation number of combined elements

Answer 6

You must assign oxidation numbers to combined elements using the periodic table

Question 7

State what is being oxidised and what is being reduced in this equation

  0       0       +2  -2 2Mg + O2 -> 2mgo

Answer 7

Magnesium (Mg) oxidation

Oxygen (O) reduction

Question 8

State what is being oxidised and what is being reduced in this equation

  0       0       +1  -1 2Na + Cl2 -> 2NaCl

Answer 8

Sodium (Na) oxidation

Chlorine (Cl) reduction

Question 9

State what is being oxidised and what is being reduced in this equation

0      0     +1  -1 2K + F2 -> 2KF

Answer 9

Potassium (K) oxidation

Fluorine (F) reduction

Question 10

State what is being oxidised and what is being reduced in this equation

+1 -1 0 0
2KCl -> 2K + Cl

Answer 10

Chlorine (Cl) oxidation

Potassium (K) reduction

Question 11

State what is being oxidised and what is being reduced in this equation

+3 -1 0 0
AlCl3 -> Al + 3Cl

Answer 11

Chlorine (Cl) oxidation

Aluminium (Al) reduction

Question 12

Define an oxidising agent

Answer 12

An oxidising agent is a substance that brings about oxidation in other substances

Question 13

Define a reducing agent

Answer 13

Define a reducing agent is a substance that brings about reduction in other substances

Question 14

What brings about reduction in redox equations

Answer 14

Oxidation

Question 15

What brings about oxidation in other redox equations

Answer 15

Reduction

Question 16

Give two examples of oxidising agents

Answer 16

Oxygen- combustion

Hydrogen peroxide-bleaching hair

Question 17

Give two examples of reducing agents

Answer 17

Sulfur oxide- bleaching agent

Carbon man oxide- removes oxygen from iron ore to convert to pure iron

Question 18

Define oxidation numbers

Answer 18

The oxidation number of an atom is the charge an atom has, or appears to have, when electrons are distributed according to certain rules

Question 19

State the rules of oxidation numbers

Answer 19

• The oxidation number of an atom in its elemental state is 0.
• The oxidation of a simple ion is equal to the charge of that ion
• Group 1= +1, group 2= +2 and group 7= -1 etc…
• The sum of oxidation number of the atoms in an ion is equal to the total charge of that ion
• Oxygen has an oxidation number of -2 except in hydrogen peroxide where it’s -1 or if it’s bonded to fluorine it’s +2
• Hydrogen has an oxidation number of +1 except in metallic hydrides where it’s -1

Question 20

What is the oxidation number of phosphorus in pcl3

Answer 20

3
Cl has an oxidation number of -1 there are 3 of them that makes their oxidation number -3. P must equal 3 equaling the overall charge to 0 therefore balancing the equation.