Test for hydrogen
Test gas with burning splint
Observation for H2 gas
- effervescence occurs
- colourless odourless gas evolved
- gas extinguishes lighted splint with a pop sound
- gas is hydrogen
Why is there a pop sound for hydrogen
Due to small explosion when hydrogen gas burns w oxygen in the air
Test for oxygen
Test gas with a glowing splint ( swipe away the fire first)
Observations for O2
- effervescence occurs
- colourless odourless gas evolved
- gas relights a glowing splint
- gas is oxygen
Why does splint start to glow again for oxygen
Cuz oxygen gas supports combustion
Observation for CO2
Effervescence occurs
Colourless odourless gas evolved
Gas forms white ppt in limewater
Gas is CO2
Why does it form white ppt
CO2 is an acidic oxide that reacts with calcium hydroxide to form insoluble calcium carbonate (white ppt) and water
What is the test for carbon dioxide?
Put the thing in btwn CO2 and limewater ( shorter end in CO2, longer one in limewater)
What is the test for ammonia?
Warm the mixture
Put damp litmus paper over the test tube
Observation for ammonia
Effervescence occuds
Colourless pungent gas observed
Gas turns damp red litmus paper blue
Gas is ammonia
Why is ammonia alkali
When dissolved in water ammonia ionises to produce hydroxide ions ( alkali property)
When to test for oxygen
When mentioned add hydrogen peroxide
When to test for ammonia
- when mention add aq sodium hydroxide & aluminium foil then warm
- base + ammonium salt –> salt + water + ammonia
When to test for carbon dioxide
- when need an a solid that’s not grey n not metal to acid ( prob a carbonate)
- asked to heat strongly
When to test for hydrogen
- if asked to add unknown solid to acid ( grey metal)
