Redox.

Question 1

Summarise the redox rules.

Answer 1

The more electronegative atom will have the negative oxidation state in more complex species. Fluorine is always -1 since it is the most electronegative so nothing trumps it. Oxygen is always +1 unless bonded to the omnipotent flourine is -1 and oxygen can be positive.
The other exception is where fluorine is in H2O2 where oxygen is -1 and hydrogen is +1.
Metals will have the oxidation states of the ions they would form.
Since you can see on the periodic table that hydrogen is more electronegative than metals in metals bonded to hydrogen the hydrogen will have a negative oxidation state and be relative to the metals.

Question 2

What is an oxidation state.

Answer 2

Oxidation state is the charge the species would have if it where an ion.

Question 3

Give the redox half equation for Cr3+ becoming Cr2O72-.

Answer 3

2Cr3+ +14H+ goes into Cr2O2 2- +6e- +7H20.

Question 4

Give the oxidation state of oxygen in H2O2.

Answer 4

O= -1 (you have the O2 2- ion in there)

Question 5

Give the oxidation state of hydrogen in NaH. Justify this answer. And give Na oxidation state.

Answer 5

Na+1 (no exceptions).
Therefore to make neutral charge H=-1
Hydrogen is the more electronegative so can take this to be the negative value.

Question 6

What is the difference in the way charges and oxidation states are written.

Answer 6

For oxidation state it is charge followed by number.

For an ion it is number followed by charge.

Question 7

What do we imagine when we use oxidation states.

Answer 7

We Imagine Everything as it it where ions.

Question 8

How should you think of oxidation Staes when there is multiple of one atom being reduced or oxidised.

Answer 8

The oxidation state is for one atom so need to multiply electrons if multiple change.

Question 9

Give the oxidation states of all the species in the following examples : KMnO4 , K2MnO4 and NaCuCl2.

Answer 9

K=+1 in all of the species as is a group 1 metal so that’s safe. There is no fluorine or hydrogen peroxide. So can safely take oxygen as -2 in all species.
For K2MnO4 : Mn=+7
For K2MnO4 :Mn=+6
For NaCuCl2 : Cu = +1 Cl= -1 Na= =1

Question 10

How should hydrogen be considered in terms of its electronegativity.

Answer 10

Its position in the periodic table is representative of its electronegativity.

Question 11

What do you need to look out for when you first start a redox atom.

Answer 11

LOOK TO BALANCE THE REDOIX ATOM AS FIRST THING , YOU WILL GET NO MARKS IF YOU MISS THIS.

Question 12

Give the redox equation for the sulphate ion becoming sulphur dioxide.

Answer 12

SO4 2- +2e- +4H+. INTO SO2 +2H2O