chemistry testing for gases.
haha i realised all the font size too small to see properly...anyway, here is a quick revision of testing for gases
Nitrogen
colourless and odourless
confirmatory test: insert LIGHTED splint, extinguishes with a pop sound
Oxygen
colourless and odourless
confirmatory test: insert GLOWING splint, the flame rekindles:)
Carbon dioxide
colourless and odourless
confirmatory test: Bubble the gas into limewater (calcium hydroxide) and white ppt will form (Calcium carbonate)
note: it turns blue litmus paper slightly red
Sulfur Dioxide
colourless, has CHARACTERISTIC BURNING SMELL OF SULPHUR
Turns blue litmus red
Confirmatory test:
-turns purple acidified potassium manganate (KMnO4) decolourised
-turns orange acidified potassium dichromate (K2Cr2O7) orange to green
H20 vapour (water vapour)
colourless, odourless
confirmatory test: test with cobalt (II) chloride paper, turns blue to PINK!
note: anhydrous cobalt (II) chloride is also used as a drying agent!:)
Chlorine
pale greenish yellow, choking smell
confirmatory test: turns blue litmus paper red, then bleached
Ammonia
colourless, pungent
confirmatory test: turns RED litmus blue
ok so basically, the neutral gases are:
-oxygen
-hydrogen
-water vapour
They are NEUTRAL TO MOIST LITMUS PAPER
Acidic gases (turn blue litmus paper RED)
-Carbon dioxide --> confirmed via limewater test
-Sulfur dioxide --> test with acidified potassium manganate/dichromate
-Chlorine --> it will turn litmus paper bleached
Alkaline gas---> ONLY ONE! SPECIAL! UNIQUE! AND SMELLY!!!!!!
it is the one and only......AMMONIA!!!:D
Collection of GASES
ok, basically, just remember, how you collect a gas depends on 2 factors--it's solubility in water, and density compared with air.
based on the table in the textbook, gases that are NOT soluble in water are:
1. Hydrogen
2. Oxygen (although slightly)
3. Carbon dioxide (slightly too)
4. Nitrogen
The rest are soluble:)
thus, these 4 gases usually use the displacement of water method
Gases that are less dense than air
1. Hydrogen
2. Ammonia
The rest are mostly denser
so, these usually use Upward delivery/ downward displacement of air
Drying of gases
Here are some drying agents:
1. concentrated sulphuric acid (H2SO4)
2. Calcium Oxide (CuO, also known as quicklime)
3. Fused Calcium chloride
4. anhydrous cobalt (II) chloride
5. Anhydrous copper (II) sulfate
Take note, don't use concentrated sulphuric acid to dry ammonia!
k that's about it, good luck for all the common tests:) and remember to smile! it helps(:
smiling song (to the tune of if you're happy and you knwo it)
If you're sad and you know it give a smile (flash a BIG smile)
If you're angry and you know it give a smile (flash a gigantic smile!)
If you're really dissapointed and you don't want to show it,
If you're really dissapointed give a smile:) (flash a HUMONGOUS smile!)
well, hope that took off some stress...
Labels: JIAWEI:D
one heart, one mind,one dance