oxidation, reduction, redox equations

Question 1

What is oxidation?

Answer 1

The loss of electrons or gaining of protons

Question 2

What is reduction?

Answer 2

The gaining of electrons or loss of protons

Question 3

What is in an oxisdising agent?

Answer 3

A species that is an electron acceptor and removes electrons from another species

Question 4

What is a reducing agent?

Answer 4

Species that is an electron donator and gives electrons to another species

Question 5

What is a disproportionation reaction?

Answer 5

When a species is oxidised and reduced simultaneously

Question 6

What is an oxidation state?

Answer 6

The hypothetical charge on an element in a compound or ion

Question 7

What is the oxidation state of an element?

Answer 7

Always 0

Question 8

What must the sum of all the oxidation states in the compound vehicle to?

Answer 8

0 or the overall charge on an ion

Question 9

Which groups in the periodic table have fixed oxidation states and what are they?

Answer 9

Group 1 = +1
Group 2 = +2
Group 3 = +3

Question 10

What is the oxidation state of hydrogen usually?

Answer 10

+1

Question 11

What is the oxidation state of hydrogen in metal hydrides? (e.g., NaH)

Answer 11

-1

Question 12

What is the oxidation state of fluorine?

Answer 12

always -1

Question 13

What is the oxidation state of halogens? What is the rule for working out the oxidation state?

Answer 13

• usually -1

- unless another element in the compound is more electronegative (e.g., ICl = +1 -1)

Question 14

What is the oxidation state of oxygen usually?

Answer 14

• 2

Question 15

What is the oxidation state of oxygen in peroxides? (e.g., H2O2)

Answer 15

-1

Question 16

How do you work out the oxidation state of an ion?

Answer 16

The oxidation state will be equal to the ions charge

Question 17

What must the overall oxidation states in a molecular ion equal to?

Answer 17

The charge on the ion

Question 18

What is the method for writing half equations?

Answer 18

1. Calculate the oxidation states on each side of the equation
2. Balance the elements changing the oxidation state
3. Sort out the electrons
4. Sort out the oxygens
5. Sort out the hydrogens
6. Check the total oxidation states are equal on both sides of the equation

Question 19

How do you sort out the electrons when writing the half equation (step 3)?

Answer 19

• If the oxidation state becomes more negative, it gains electrons
• is oxidation state becomes more positive, it loses electrons

Question 20

How do you sort out the oxygens writing a half equation (step 4)?

Answer 20

• For every oxygen gained you add one water molecule

- For every oxygen lost you remove one water molecule

Question 21

How do you sort out the hydrogens when writing a half equations (step 5)?

Answer 21

• for every hydrogen atom gained, add one H + ion

- for every hydrogen at lost, remove one H+ ion

Question 22

How do you combine half equations?

Answer 22

Adding equations together so that the electrons cancel out

Question 23

How do you cancel out electrons when combining half equations?

Answer 23

Multiply each half equation to make the same number of electrons in each equation