volumetric analysis of oxidation reduction reactions

KMnO4

formula for potassium permanganate

potassium manganate VII

alternative name for potassium permanganate

purple coloured solid

how does potassium permanganate come in the lab

cannot be obtained in a highly pure state, decomposes in sunlight, decomposes in heat

why is potassium permanganate not a primary standard

Mno4- + 8H+ +5e- = Mn2+ + 4H2O

formula for potassium permanganate acting as an oxidising agent in an acidic solution. it gains 5 e-

+7 purple to +2 colourless

how does the oxidation state of potassium permanganate change in the half reaction as well as colour.

sulfuric acid

what is added to supply KMnO4 with h+ ions so it can undergo redox reaction

the KMnO4 would oxidise it to Cl2

why cant HCL be used instead of H2SO4

brown due to the formation of manganese dioxide MnO2

what colour does the manganese ion change to in a neutral or basic solution

+7 to +4

what oxidation state change occurs to Mn in a basic or neutral solution

self indicating

why dont you need an indicator with KMnO4

read top of meniscus

weird practice with KMnO4

intense colour, low solubility, effective oxidising agent

why do we use dilute potassium permanganate

titrate against Fe2+ ions

how do we determine the concentration of KMnO4

5

how many e- can a MnO4- accept when reacted with Fe2+ ions

1

how many e- can Fe2+ lose to MnO4-

1:5

ratio of KMnO4:Fe2+

not a primary standard (crystals slightly oxidised by air, efflorescent)

why cant Fe2+ be obtained from FeSO4’7H2O

efflorescence

the spontaneous loss of water of crystallisation to the air

ammonium iron II sulfate

where dow e get the Fe2+ ions

(NH4)2’FeSO4’6H20

formula of ammonium iron ii sulfate

well stabilised and isnt efflorescent

why can we use ammonium iron ii sulfate despite it being hydrated

392

relative molecular mass of ammonium iron ii sulfate

prevent Fe2+ from oxidising to Fe3+ by oxygen in the air

why must ammonium iron ii sulfate be dissolved in water containing diluted sulfuric acid

KMnO4

what goes in the burette when standardising a solution of a solution of KMnO4 against ammonium iron ii sulfate

ensure sufficient supply of h+ ions, so all MnO4- are reduced to Mn2+

why is excess sulfuric acid added to the conical flask of ammonium iron ii sulfate when standardising KMnO4 against it

brown precipitate

what happens if no or insufficient sulfuric acid is added to the conical flask for KMnO4 against ammonium iron ii sulfate

purple to clear to pink

colour change seen in the conical flask in the standardising of KMnO4 against ammonium iron ii sulfate m(3, including one excess drop)

KMnO4 again

what goes in the burette when titrating KMnO4 against iron tablets comboed with H2SO4 (sulfuric acid)

yes

is an excess of sulfuric acid added to the iron tablet experiment

purple to clear to pink 2

colour change in iron tablet experiment

Na2S203

sodium thiosulfate formula

colourless crystalline solid hydrated

typical way we find sodium thiosulfate

S2O3 2-

thiosulfate ion formula

I2 + 2S203 2- = S4O6 2- + 2I-

formula for the reaction between iodine and sodium thiosulfate to get a tretrathionate ion

S4O6 2-

tetrathionate ion formula

cant be obtained in a highly pure state, efflorescent

why isnt sodium thiosulfate a primary standard

titrate it against a standard solution of iodine

how do we find out the concentration of sodium thiosulfate

sublimes

why cant a standard solution of iodine be made up by weighing it directly

titrate KMnO4 against excess potassium iodide solution

how do we standardise a solution of iodine

2MnO4- + 10I- + 16h+ = 2Mn2+ + 5I2 + 8H2O

equations between mno4- ion and iodide ion, with the multiplication of 5 and 2

need 5 in other equation

why do we have to multiply the 2I- by 5

we need 2 in the other equation

why do we multiply the mno4- by 2

2:5

ratio of KMnO4 to iodine formed

reddish brown to pale yellow to colourless

colour change in an iodine/thiosulfate titration

pale yellow

when do we add starch to iodine/thiosulfate

blue black to colourless

colour change of starch

will absorb the iodine earlier

why dowe add starch only at colourless