24.5 Redox And More Colour Flashcards
What does the FE2+ / MNo4- redox reaction and colour change look like
What species cause colour change?
Fe2+ is reduced to Fe 3+
MNO4 - is oxidised ti form MN2+ ions
Thus the colour change is PURPLE to colourless, purple MNO4-
What is the Fe3+ / 2I- redox and Colour change
What species dominates colour
Fe3+ reduced to Fe 2+
This causes a colour change of yellow to pale green ions
2I- oxidised to iodine
This for,s a colour change producing brown iodine
Brown colour takes precedence
Cr2o7 2- redox to cr 3+ with zinc
Colour change
Cr2o72- reduced ti cr 3 + ions
Colour change orange to green
Zinc is just reduced ti zn 2+
Redox of Cipper 2+ ions to copper 1 + ions with iodine
WHAT TWO PRODUCTS ARE PRODUCED + products
Cu2 + reduced to copper + calm
2I- ixidised ti iodine brown calm
But thr reduced CU+ also reavts with I- to form a WHITE predicate of CUI
Overall reaction looks like
2cu + 4I- —> 2CuI + I2
What is disporponation and how does it happen with cu2+ ions normally (what state are they)
When same species is both oxidised and reduced
Normally happens when copper 2+ ions are aqeuous
Remmeber all the anions test for cabrkante , SUKFATE, and halides
Nitric acid = effervescence , barium nitrate = white preicpste , silver nitrate = silver halide milk cream butter
What was further test for the halogens with ammonia?
After reacting with silve nitrate And getting milk cream butter
The SOLUBITILTY of ammonia decreases lower you go
So milk one the most soluble, will be soluble in dilute ammonia
Cream will only be soluble in concentrated
Butter INSOLUBLE with concentrated
Why order must be carbonate, SUKFATE then silver halid
1) must do silver test last because silver makes two white predicates with SUKFATE ions and carbonate = bad
2) must do barium second because barium forms white predicate with a carbonate too
1) doing carbonate first ensures you know exactly carbonate bevause others will never react to effervescence
This way say ou testing for chlorine ions and you haven’t tested for sukfate, a white predicate of silver sulfste will form and you gonna get confused
How to do it on a mixture of ions
Add acid till stop bubbling so all cabrknsge gone
2) add virus nitrate then filter if any prefipate made
3) finally do halide with ammonia
Can’t use sukfruic acid or hydrochloride acid bevause barium SUKFATE predicate and chlorine ions
Redox colours summary
Mn2o4- becomes mn2 + colourless ( reduction)
Fe 2+ becomes fe 3 +
2I- oxidation ti become brown iodine
Fe 3+ becomes fe 2 +, yellow to pale green but overruled by brown
Cr2o72- becomes cr 3+ reduction
Zinc oxidisation
Cu2 + reduction to cu +
I2 - become sidoien brown
But then cu + reavts with I- to become white predicate too
