Colours And Tests Flashcards
Carbonate ion test
How to don+ confirm
1) nitric acid
- effervescence
- collect gas bubble through lime water (ca(OH)2 )
If co2 then jt will form a white precipitate of calcium carbonate , therefore if co2 released it was a carbonate
Sulfste test
Barium NITRATE to solution
- if sulphate ion present, white precipitate Ba(So4) forms
(Don’t use barium chloride if need to do halide test after)
Halide tests
Colours + HOW TO DIFFERENTIATE IF COLOURS ARE SIMILAR (easy way to remember the concs)
Silver nitrate
- based on colour of prefipate milk cream butter (white cream yellow) is the halide
- to confirm , dissolve in ammonias
- first dissolved in conc and weak
- second dissolved in comc only
- 3rd doesn’t dissolve at all (conc )
Easy way to remember is solubility increase group 2 so decrease group 7.)
Sequence of tests
Why pretty much
1) carbonate first
- only carbonates release co2 so can safely rule out,
- baroum CARBONATE IS A WHITE PRECIPITATE
2) sulfste test 2nd
- SILVER SULFSTE + AND SILVER CARBONATE FORM PRECIPITATED TOO
4) therefore must do halide last
What acid and solution to use and why (sulfruic nitric what?)
Nitric acid, barium nitrate , silver nitrate, so that you don’t introduce RSNDOM sulfste , chlorine ions if doing series of tests
How ti do tests to identify mixture of compounds ? For thr csbrknste sulfste halide
1) add nitric acid till stop bubbling, now you know all carbonate reacted
2) add excess barium nitrate, any barium sulfste precipitate out, filter
3) do halide test, with ammonia to check
Don’t use sulfruic or hydrochloric acid etc
Ammonium ion cation test
WHAT REAGENT NEEDED
what way to confirm
REACT NAOH with ammonium soltuoj
Heat up
Ti confirm , add DAMP litmus paper red near neck, should turn blue
AS tests summary
4 tests + required order and why
1) carbonate = nitric acid = effervescence = collect + bubble in like water (Ca(OH2) ) and should form white calcium carbonate precipitate
2) sulfste = barium nitrate = white precipitate barium sulfate
3) halide = silver nitrate = milk cream butte , add conc / dilute (decrease solubility lower you go) to differentiate
4) am,onium = NaOH to solution, heat, use red litmus paper becomes blue
Must do carbonate sulfste then silver, as barium carbinste , silver carbonate and silver sulfste all are precipated (white)
Condition for sodium hydroxide in disprortijstion with chlorine
Cold and dilute
Fe 2+ fe 3+ when in solution colour
Pale green fe 2+
Yellow fe 3+
Cr 6+ cr 3 + colour in solution
How to remember easily
We now acidified potassium dichromate is an oxidising agent. Therefore, the chromium must be REDUCED
=cr6+ is orange
Cr 3+ is GREEN
Hexa aqua copper basic colour
How is it formed
PALE BLUE
Formed when copper sulfste dissolved in water
1) hexa aqua copper resctions with ammonia!
All 3 colour changed
Drop by drop,
- initially will get Cu(OH)2 precipitate blue formed
- then dissolved in ammonia to give Copper 4 ammonia 2 water DARK BLUE
2) hexa aqua copper resvtion with chlorine ions
What is intial and final colour
- what happens if you add water back to new complex ion ?
- why is there a green colour seen if slowly add chlorine ?
- as chlorine ions are big, remember only 4 can react
- this forms [cu (cl4)] -2 which is YELLOW
2) adding back with water reverses and makes it yellow to pale blue again
3) a green intermediate is formed as adding chlorine ions as the yellow and pale blue mix, don’t fret
S
3) what is chromium hexa water colour base
This is violet
3) chromium hexa water resvtion with ammonia dropwise
All 3 collour changes
- intially precipitate formed = Cr (Oh)3 which is GREY GREEN
RRECIPITATE - then dissolved in excess ammonia to form CHROMIUM HEXA 6 AMMONIA
Which is VIOLET
What is the source for chlorine ions for 2)
Concentrated HYDROCHLROIC ACID
Precipitation
1) Cu2+
Blue to blue precipated (Cu (Oh)2
Precipitation
2) Fe 2+
What else
Pale green to green (Fe(Oh)2
Then in air oxidise to Fe 3+ thus Fe (OH) and BROWM
Preiciaptiom
Fe3+
Fe 3+ is yellow and becomes orange brown precipated fe (Oh)3 as seen before
Rediaptiom 4)
Mn 2+
Mn 2+ pale pink and become light brown in Mn(OH)2 precisiptr
5) precipitation
Cr 3+
Special case unlike other 4 REMEMBER
Cr 3+ is VIOLET
Becomes Cr(OH)3 green grey precipated (as seen before)
BUT DISSOLVED IN EXCESS NAOH
Giving [Cr (OH)6] -3 which is DARK GREEN
Remember these all REACT and form same precipated with ammonia and NaOH except
They all do, and all use same equations so don’t get confused
- however Cr 3+ does make the precipated but doesn’t dissolve in excess ammonia to form thr Comolex hexa h dry oxide Cromium dark hreen
All colours ligand + precipitation
Ligand
1) hexa aqua copper (light blue) with ammonia = precipated Cu (Oh)2 blue = dissolved in excess to 4 ammonia 2 water copper (dark blue) complex ion
2) hexa aqua copper (light blue) with hcl = cu cl4 2- (yellow). Reversible + green intermediate can be formed as colours mix
3) hexa aqua chromium is Violet . Add ammonia = cr(Oh)3 green grey preicpste = dissolved in excess to form hexa ammonia chromium purple,
Preiciaptiom
1) Cu2+ blue to blue preicpste
2) fe 2+ light green to green , to orange brown as oxidises to Fe3+ I’m air
3) fe3+ yellow to orange brown like ^
4) mn 2+ pale pink to light brown
5) cr3+ Violet becomes cr (oh)3 green Grey precipated as seen before = cr (Oh)6 -3 compex dark green
All react the same with ammonia, except when cro (Oh)3 excess ammonia forms cr 6 ammonia no cr 6 hydroide …
Z
Extra resvtion and colours
Copper iodine
Need to know
2 Cu 2 + + 4I- —> 2CuI + I2
Copper iodine is a white precipated , iodine is a brown colour
What colour is pure copper (s) which is achieved in disprotiinstikn resvtion
And cu (so4)
Cu (s) brown
Cu(so4) is blue
Colour of sulfur
Like orange
Colours of hexa aqua Fe 2+ and Fe3+, for anything?
Just like how cu2+ hexa aqua is blue too (although light ) they take rhe SAME COLOUR Z
THUS light green and orange brown
