IONIC FORMULA

Question 1

How is an unknown oxidation number found in an ion/compound?

Answer 1

Using the oxidation state rules, and the charge of the compound, the oxidation number of an element can be determined.

Sulphate ion for example (SO4^2-)
-2 charge
Oxygen has a oxidation number of -2 in this case
x + -8 = -2
x = 6, so the oxidation number of sulphur in SO4^2- is 6

Question 2

What are half equations?

Answer 2

More simplified reactions used to show the important ions and compounds in a reaction and the transport of electrons

Question 3

How are simple half equations balanced?

Answer 3

Electrons are used; the charge on both sides of the reaction have to be the same and the charge on 1 side goes down by 1 for each electron added

(Pb^2+ + 2e- ==> Pb)

Question 4

How are complex half equations balanced?

Answer 4

Hydrogen ions and water can also be used, if oxygen is present in the compound
For each water molecule on 1 side of the reaction, there will be 2 hydrogen ions that increase the charge by 2+ (1 per hydride ion); this can still be balanced by electrons

(VO2^2+ + H2O ==> VO2^+ + 2H+ + e^-)

Question 5

How are half equations combined?

Answer 5

If the amount of electrons are unequal, multiply the smaller value until they are
Combine the 2 equations
Cancel out any electrons, ions, compounds, etc. that appear on both sides of the reaction