m2 - redox

Question 1

oxidation number rules

Answer 1

metals by themselves = 0
oxygen in compounds = -2
hydrogen in compounds = +1

Question 2

oxidation is…

Answer 2

loss of electrons
increase in oxi number

Question 3

reduction is

Answer 3

gain of electrons
decrease in oxi number

Question 4

oxidising and reducing agents

Answer 4

oxidising agents are themselves reduced (accept electrons)
reducing agents are themselves oxidised (donate electrons)

Question 5

half equation Li to Li+
Cu2+ to Cu

Answer 5

Li -> Li+ + e- (x2)
Cu2+ + 2e- -> Cu (x1)

2Li + Cu2+ -> 2Li+ Cu

Question 6

how to balance more complex half equations
(MWHE)

Answer 6

balance:
Metal => H2O => H+ => e-

oxygen using Water
hydrogen using H+
charges using Electrons

(also can use oxi states)

Question 7

when given overall equations, how do you balance them using oxi numbers

Answer 7

work out oxi numbers to see what is oxidised and what is reduced
then make them equal by multiplying

eg if you have +2e- and -4e-, multiply +2e- by 2

Question 8

iodine thiosulphate titration half equations

I-
S2O3 2-

Answer 8

unknown + I- (excess) —> I2

I2 + thiosuphate (known) —> I-

Question 9

colours throughout iodine thiosulphate titration

Answer 9

red-brown I2 in conical flask,
adding thio ions will make it go colourless but we need to see exact change
so one it reaches straw yellow we add starch so it will go blue/black

Question 10

iron and manganate titration colours

Answer 10

purple in burrette, colourless in conical
turns a pale pink once Mn is in excess