Qualitative Tests Flashcards
CO2 Carbon Dioxide
Bubble gas produced through limewater - changes from colourless to milky
H2 Hydrogen
Place a burning splint into contact with the gas. A pop is produced.
O2 Oxygen
Place a glowing splint into contact with the gas. The splint relights.
Cl2 Chlorine
Damp litmus paper turn red then bleaches.
NH3 Ammonia
Glass rod dipped in concentrated HCl - white fumes and smoke.
HCl Hydrochloride
Glass rod dipped in concentrated Ammonia solution - white fumes and smoke.
SO2 sulfur dioxide
Bubble gas produced through potassium dichromate solution - changes from orange to green
Flame Test Method
- Dip nichrome wire in conc. HCl then place in blue Bunsen flame.
- Repeat until no colour observed.
- Dip wire into sample then into flame.
- Record colour observed.
Li+
crimson
Na+
yellow
K+
lilac
Ca2+
brick red
Ba2+
green
Cu2+
blue-green
Nh4+
- 5cm3 of NaOH solution in a test tube.
- Add spatula measure of sample.
- Warm gently.
- If NH4+ ion present, NH3 with a pungent smell will be evolved.
- Confirm with NH3 test.
Sulfate Ion SO4 2-
- Dissolve a spatula measure of sample in nitric acid.
- Add 2-3cm3 of Barium Chloride solution.
- White ppt of Barium Sulfate will form.
- Ba2+(aq) + SO4 2-(aq) > BaSo4 (s)
Halide Ions Cl-, Br-, I-
- Dissolve a spatula measure of sample in Dilute Nitric Acid.
- Add 2-3cm3 of Silver Nitrate Solution.
Cl-: white, Br-: cream, I-: yellow - Add dilute NH3 (Cl dissolves)
- Add conc. NH3 (Br dissolves)
I- will not dissolve in NH3.
Carbonate ions CO3 2-
- Place 5cm3 of Dilute Nitric Acid in a test tube.
- Add a spatula measure of the sample.
Obs: Effervescence and solid disappears. - Confirm by bubbling gas through limewater (turns milky).
Iodine
Add a few drops of aqueous starch to iodine solution - turns blue-black.
