Redox

Question 1

What do oxidation states indicate?

Answer 1

The number of electrons that an element has accepted or donated.

Question 2

What is an advantage of oxidation states over charges?

Answer 2

They can also be applied to covalent compounds.

Question 3

What is a key skill required in calculating oxidation states?

Answer 3

The ability to systematically apply rules to questions.

Question 4

What is the oxidation state of uncombined elements?

Answer 4

0.

Question 5

What is the sum of oxidation states in a compound?

Answer 5

0.

Question 6

What does the sum of oxidation states equal in a complex ion?

Answer 6

The charge on the ion.

Question 7

What is the oxidation state of group 1 metals in a compound?

Answer 7

+1.

Question 8

What is the oxidation state of group 2 metals in a compound?

Answer 8

+2.

Question 9

What is the oxidation state of aluminium in a compound?

Answer 9

+3.

Question 10

What is the oxidation state of hydrogen in a compound?

Answer 10

+1, except in metal hydrides where it is -1.

Question 11

What is the oxidation state of oxygen in a compound?

Answer 11

-2, except in peroxides where it is -1.

Question 12

According to Rule 1, what is the oxidation state of O in O2?

Answer 12

0.

Question 13

What is the oxidation state of S in HSO4?

Answer 13

+6.

Question 14

Fill in the blank: The oxidation state of each hydrogen in HSO4 is ______.

Answer 14

+1.

Question 15

Fill in the blank: The oxidation state of each oxygen in HSO4 is ______.

Answer 15

-2.

Question 16

True or False: The sum of oxidation states in HSO4 is equal to +6.

Answer 16

False.

Question 18

What is the first step in balancing half equations?

Answer 18

Balance the species with the variable oxidation state

Question 19

How do you write a half equation that shows the reduction of H2SO4 to SO2?

Answer 19

H2SO4 → SO2 + 2H2O

Question 20

What is the oxidation half equation for Fe?

Answer 20

Fe → Fe2+ + 2e

Question 21

What is the purpose of adding electrons in half equations?

Answer 21

Balance charge

Question 22

True or False: Electrons are added to the side with a higher positive charge to balance the equation.

Answer 22

True

Question 23

What do you add to balance hydrogens in half equations?

Answer 23

H+ ions

Question 24

What do you add to balance oxygens in half equations?

Answer 24

Water molecules

Question 25

How do you balance the following half equation: H2SO4 + 2H + 2e → SO2 + 2H2O?

Answer 25

Balance the charges and atoms on both sides

Question 26

Fill in the blank: To balance the equation Fe → Fe2+, _______ are added to the left-hand side.

Answer 26

2 electrons

Question 27

What is the balanced equation for the oxidation of Fe?

Answer 27

Fe → Fe2+ + 2e

Question 28

What is the final step in writing half equations?

Answer 28

Ensure all charges and atoms are balanced

Question 29

What is the key rule for balancing half equations?

Answer 29

Follow the order of balancing species, charge, hydrogens, and oxygens

Question 30

How to write the half equation full steps

Answer 30

Balance the species with the variable oxidation state ( by balancing the big numbers or small n.os eg. 2cl = cl2 (the n.o of the atoms)) Balance oxygen by adding water Balance hydrogen by adding H+ ions Balance the charge by adding electrons

Question 33

What does the term REDOX represent?

Answer 33

A combination of oxidation and reduction.

Question 34

What is required for something to be oxidised?

Answer 34

An oxidising agent.

Question 35

Define oxidation.

Answer 35

A process in which electrons are lost.

Question 36

Define reduction.

Answer 36

A process in which electrons are gained.

Question 37

What is a reducing agent?

Answer 37

A substance that donates electrons to another species.

Question 38

What is an oxidising agent?

Answer 38

A substance that accepts electrons from another species.

Question 39

Fill in the blank: A reaction in which electrons are lost is called _______.

Answer 39

Oxidation.

Question 40

Fill in the blank: A reaction in which electrons are gained is called _______.

Answer 40

Reduction.

Question 41

True or False: You cannot have oxidation without reduction.

Answer 41

True.

Question 42

What must you do before defining key terms in exam questions?

Answer 42

Read exam questions carefully.

Question 43

In a chemical reaction, what does the oxidising agent do?

Answer 43

It reduces another species.

Question 44

What does a reducing agent do in a chemical reaction?

Answer 44

It oxidises another species.

Question 45

Fill in the blank: In redox reactions, oxidation and reduction occur _______.

Answer 45

Simultaneously.

Question 46

What is the role of electrons in oxidation?

Answer 46

Electrons are lost.

Question 47

What is the role of electrons in reduction?

Answer 47

Electrons are gained.

Question 49

What is the first rule for combining half equations?

Answer 49

One half equation must show oxidation and one must show reduction.

Question 50

In oxidation half equations, where are electrons added?

Answer 50

On the right-hand side.

Question 51

In reduction half equations, where are electrons added?

Answer 51

On the left-hand side.

Question 52

What must be equal before combining half equations?

Answer 52

The number of electrons in each half equation.

Question 53

How do you make the number of electrons equal in half equations?

Answer 53

Multiply them up to the lowest common denominator.

Question 54

What should be included when adding the equations together?

Answer 54

All reactants and products from both equations.

Question 55

What must be removed after combining half equations?

Answer 55

Any spectator ions or electrons.

Question 56

Fill in the blank: H2SO4 + 2H + 2e → SO2 + 2H2O represents _______.

Answer 56

[reduction]

Question 57

Fill in the blank: Fe2 → Fe + e represents _______.

Answer 57

[oxidation]

Question 58

What is the final combined equation from the half equations H2SO4 + 2H + 2Fe2 → 2Fe3+ + SO2 + 2H2O?

Answer 58

H2SO4 + 2H + 2Fe2 → 2Fe3+ + SO2 + 2H2O.

Question 59

True or False: Spectator ions are included in the final REDOX equation.

Answer 59

False.