IIT JEE , AIEEE Forum - Chemistry , Inorganic Chemistry

Mr.IITIAN007

Can somebody please tell me the observations of preliminary tests for the ions Fe2+,Fe3+ and Al3+.Preliminary tests means dry heating test,charcoal cavity test,cobalt nitrate test,flame test and barax bead test.If there is no observation for an ion mentioned above,let me know here.Please post them fast.

aashish

cobalt nitrate test:-

on adding 2 drps. of Co(NO3)2 to white residue after charcoal cavity test. Blue colour indicates presence of Al3+

borax bead test:-

for iron:-

oxidiing flame:yellowish brown whwn hot, pale yellow whwn cold,

reducing flame:-green,hot and cold

chromium:oxidiing flame & reducing flame:green

if u require for wet tests, plz ask

rahul_12345

THESE ARE THE PRELIMINARY TESTS FOR THE THREE IONS YOU MENTIONED ABOVE

ACTION OF SODIUM HYDROXIDE SOLUTION

To a solution of the test substance, sodium hydroxide solution is added drop by drop until it is in excess (test with red litmus paper). Some solutions may be acidic to begin with (test the original solution with blue litmus paper); in such cases nothing will happen until the acid has all been neutralised

White precipitate soluble in excess NaOH: Al³⁺, Zn²⁺, Pb²⁺.

Dirty-green precipitate, turning brown on standing: Fe²⁺

Foxy red (rust coloured) precipitate: Fe³⁺.

The action of aqueous ammonia solution

To a solution of the test substance, ammonia solution is added drop by drop until it is in excess (test with red litmus paper). Some solutions may be acidic to begin with (test the original solution with blue litmus paper); in such cases nothing will happen until the acid has all been neutralised.

White precipitate insoluble in excess ammonia: Mg²⁺, Ca²⁺, Al³⁺, Pb²⁺.

Dirty-green precipitate, turning brown on standing: Fe²⁺.

Foxy red (rust coloured) precipitate: Fe³⁺.

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Cheers!

Mr.IITIAN007

Hey Aashish!!!!! Thanks . But what about flame test and and dry heating test the remaining ions??????????????And Rahul very very thanks.But I particularly want dry heating,charcoal cavity,flame and cobalt nitrate test.

vineet513

for Ferric on adding naoh soln it would give reddish colour ppt whereas for ferrous it would give dirty green ppt. and for al3+ it would give white ppt.

magiclko

http://webmineral.com/help/FlameTest.shtml

What metals do colors indicate?

Color	Metal
Red	Carmine: Lithium compounds. Masked by barium or sodium. Scarlet or Crimson: Strontium compounds. Masked by barium. Yellow-Red: Calcium compounds. Masked by barium.
Yellow	Sodium compounds, even in trace amounts. A yellow flame is not indicative of sodium unless it persists and is not intensified by addition of 1% NaCl to the dry compound.
White	White-Green: Zinc
Green	Emerald: Copper compounds, other than halides. Thallium. Blue-Green: Phosphates, when moistened with H₂SO₄ or B₂O₃. Faint Green: Antimony and NH₄ compounds. Yellow-Green: Barium, molybdenum.
Blue	Azure: Lead, selenium, bismuth, CuCl₂ and other copper compounds moistened with hydrochloric acid. Light Blue: Arsenic and come of its compounds. Greenish Blue: CuBr₂, antimony
Violet	Potassium compounds other than borates, phosphates, and silicates. Masked by sodium or lithium. Purple-Red: Potassium, rubudium, and/or cesium in the presence of sodium when viewed through a blue glass.

Symbol	Name	Color
As	Arsenic	Blue
B	Boron	Bright Green
Ba	Barium	Light green
Ca	Calcium	Red-orange
Cs	Cesium	Pale violet
Cu(I)	Copper(I)	Blue
Cu(II)	Copper(II) (non-halide)	Green
Cu(II)	Copper(II) (halide)	Blue-green
Fe	Iron	Gold
In	Indium	Blue
K	Potassium	Lilac
Li	Lithium	Crimson
Mn(II)	Manganese(II)	Yellowish green
Mo	Molybdenum	Yellowish green
Na	Sodium	Intense Yellow
P	Phosphorus	Pale bluish green
Pb	Lead	Pale green
Rb	Rubidium	Pale violet
Sb	Antimony	Pale green
Se	Selenium	Azure blue
Sr	Strontium	Crimson
Te	Tellurium	Pale green
Tl	Thallium	Pure green
Zn	Zinc	Bluish green

magiclko

check out the following link, it will give all about qualitative analysis

http://wulfenite.fandm.edu/labtech/qualanal.htm

Mr.IITIAN007

Hey thanks magilco and vineet.

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