Physical Unit 1.7: Redox

Question 1

what are the oxidation state rules?

Answer 1

an element by itself - 0
an ion - charge of the ion
group 1 metals - +1
group 2 metals - +2
hydrogen - +1 with non-metals & -1 with group 1/2 metals
oxygen - always -2 except peroxides, superoxides or with fluorine - -1
fluorine - always -1
chlorine, bromine & iodine - always -1 except with oxygen or halogen higher in group

sum of oxidation states = charge on the ion or 0 for a neutral compounds

Question 2

how do you construct redox half equations?

Answer 2

1. identify element of variable oxidation state & balance it
2. add H2Os to balance the oxygens
3. add H+s to balance the hydrogens
4. add e-s to balance charges

Question 3

how do you combine half equations to make full equations?

Answer 3

must have same # of e-s on each side
so multiply the half equations so they have the same e-s
then cancel out

Question 4

how do you identify a process as reduction or oxidation?

Answer 4

oilrig:
oxidation is loss of e-s
reduction is gain of e-s

Question 5

what is an oxidising agent?

Answer 5

the species that is reduced (oxidation state decreases)

Question 6

what is a reducing agent?

Answer 6

the species that is oxidised (oxidation state increases)

Question 7

what is disproportionation?

Answer 7

in a disproportionation reaction, a species is simultaneously reduced & oxidised

Question 8

define oxidation state

Answer 8

the charge a species would have if it were an ion