Test for - anions Flashcards
What is the test for chlorine gas.
Blue litmus paper —–> white litmus paper
Why does the litmus paper go red before going white for the chlorine test?
Because chlorine is acidic
Test for oxygen
glowing splint relights inside a test tube.
Test for CO2
Calcium hydroxide (limewater) goes from... colourless ---> cloudy
Test for Hydrogen
Squeaky pop test
Why do we hear a squeaky pop?
Because the hydrogen reacts very quickly with the oxygen in the air to form H2O.
What are the three tests for Anions?
- Carbonate test
- Sulfate test
- Halide test
Carbonate test.
Explain the method.
Add a DILUTE acid to a carbonate.
It effervesces and produces CO2 gas.
Use the CO2 test to check if CO2 is present.
if CO2 is present, then it is a carbonate.
Ionic equation for carbonates
remove the spectator ions.
CO3 2- (s) + 2 H+ (aq) —–> CO2 (l) + H2O (g)
Ionic equation for hydrocarbonates.
HCO3 - + H+ —–> H2O + CO2
Just add a H next to the Carbonate
and remove the 2
Why does the limewater go cloudy?
Because the CO2 gas reacts with the calcium hydroxide to produce a white precipitate which turns the limewater cloudy.
Sulfate test.
Explain method.
Add DILUTE HCl to check if it is a carbonate first.
if fizzes —> it’s a carbonate
no fizzing —> add the sulphate.
Add the barium chloride BaCl2
Forms a white dense barium sulphate precipitate.
Ionic equation for sulfates.
Ba 2+ (aq) + SO4 2- (aq) —–> BaSO4 (s)
Test for Cl-
ionic equation
Chlorine Cl-
- add silver nitrate AgNO3
- forms white precipitate —> AgCl (s)
- dilute NH3 is added and AgCl dissolves.
Ag+ (aq) + Cl- (aq) —–> AgCl (s)
Test for Br-
ionic equation
Bromide Br-
- add AgNO3
- forms a cream precipitate —-> AgBr (s)
- dilute NH3 is added and nothing happens
- concentrated NH3 is added and AgBr dissolves
Ag+ (aq) + Br- (aq) —-> AgBr (s)
