topic 3: redox 1 Flashcards
oxidation (in terms of electrons)
loss
- increase in oxidation number
reduction (in terms of electrons)
gain
- decrease in oxidation number
elements ON
0
Group 1 metal ON
+1
group 2 metals ON
+2
Aluminium ON
+3
H ON
+1
EXCEPT IN METAL HYDRIDES IT BECOMES -1
F ON is alllllways
-1
O ON
-2
Peroxide ON
O2 (2-)
fluroine takes precedent
Cl,Br,I ON
-1
except when with oxygen and fluorine
oxidising agent is …
- ELECTRON ACCEPTOR
- species causing another element to oxidise
- it is reduced itself
reducing agent…
- ELECTRON DONOR
- species causing another element to be reduced
- it is oxidised itself
redox reaction
reaction where both oxidation and reduction occurs
disproportionation
an element in a SINGLE SPECIES simultaneously oxidises and reduces
in acidic conditions (balancing redox)
- h2o for oxygrn
- add h+ for hydrogen
in basic conditions (balancing redox)
DO AS IF ACIDIC (h2o then h+)
- add the same OH as h+ to BOTH SIDES
- cancel
superoxide
(o2)-
what is combined in redox titrations
reducing agent and oxidising agent
manganate 7 ion
MnO4-
potassium manganate titrations
- mno4 - to mn2+ (reduced)
- fe 2+ to fe3+ (oxidised)
- must add acid to the iron
which acid to use for potassium manganate titration and why
- dilute sulfuric acid
- doesnt oxidise under these conditoins, doesnt react with manganate (7) ions
why not use HCl for manganate titrations
can be oxidised to chlorine by the manganate (7) ions
why not use HNO3 for manganate titrations
may oxidise the substance
why not use ethanoic acid for manganate titrations
too weak
why not use CONC sulfuric acid for manganate titrations
may oxidise the substance
indicator for potassium manganate titrations
-mno4 2- is purple
- mn2+ is colourless
iodine thiosulphate titration
- XS potassium iodide added to oxidising agent
- brown iodine formed
- iodine is titrated with sodium thiosulphate, which oxidises it back to colourless iodide ions
- STARCH INDICATOR IS ADDED WHEN PALE YELLOW, GOES BLUEBLACK TO COLOURLESS
