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Ch. 11 Qualitative Analysis - Coggle Diagram
Ch. 11 Qualitative Analysis
Test for Cations
Things to consider:
Colour of ppt.
Colour change in solution
Solubility of ppt.
Reagents
Ammonium
Sodium Hydroci
NaOH:
Fe2+: Green ppt (TM so coloured compound)
Insoluble in excess and ppt turns brown on standing
Fe3+: Red-brown ppt (TM so coloured compound)
Insoluble in excess
Zn2+: White ppt.
Ppt. is insoluble in excess
Al3+ : White ppt.
Ppt. is soluble in excess to form a colourless solution
Cu2+: Light blue ppt. (TM so coloured compound)
Insoluble in excess
Ca+: White ppt.
Ppt. is soluble in excess to form a colourless solution
Cations that dissolve in NaOH: ZAP (Zn2+, Al3+, K+)
Cations that dissolve in NH4: CuZ (Cu2+, Zn2+)
NH4:
Fe2+: Insoluble in excess and precipitate turns brown on standing
Fe3+: Insoluble in excess
Cu2+: Soluble in excess and forms a dark blue solution
Ca2+: No ppt. No change is observed
Al3+: Insoluble in excess
Zn2+: Soluble in excess and frms a colourless solution
Test for Anions
Dilute nitric acid and silver nitrate
Cl-: White ppt. AgCl is formed
I-: Yellow ppt. AgI is formed
Dilute nitric acid and barium nitrate
SO4 2-: White ppt. BaSO4 is formed
Add dilute acid, bubble gas through limewater
CO3 2-: Effervesence is observed. White ppt. is formed with limewater (CaCO3). --> CO2 gas is produced
Add aq NaOH, piece of aluminium and warm the mixture gently. test w/ litmus paper
NH4-: Effervsence is observed. Damp Red litmus paper turns blue. Ammonia gas is produced
Odorless, Colourless gases
Hydrogen: test w/ lighted splint. Lighted splint extinguishes w/ a pop sound if hydrogen is present
Oxygen: Test w/ glowing splint. Glowing splint relights w/ a pop sound if oxygen is present
CO2: Bubble gas through limewater. White ppt. f
Pungent Gases
Ammonia: Test w/ damp red litmus paper which wll t
Cl-: Damp blue litmus paper turns red and turns bleached
SO 4 2-: Place a piece of potassium maganate (VII) at mouth of test tube which turns from purple to colourless