A Level Chemistry Qualitative Analysis Notes
You can use this set of notes for revision. It builds on basic QA knowledge from the A
level data booklet that is provided for you during theory/practical exams.
It would be ideal to memorise such that you can look at the left column of test and be
able to think of what are the possible outcomes, what could you be testing for. This will
help you greatly in QA practical exams and theory exams.
Tests Possibilities
Cations
1. Add carbonate A) Acidic high charge cation
Al3+, Cr3+, Fe3+: white/grey-green/reddish
brown ppt formed, ppt insoluble in excess, CO2
gas (colourless gas forms white ppt with
limewater)
B) acid: CO2 gas (colourless gas forms white
ppt with limewater)
C) carbonate ppt only. (Ba2+, Ag+, Ca2+, Zn2+,
Mg2+, Mn2+, Cu2+, Fe2+). Note that for Fe2+,
green ppt turns brown on contact with air. Mn2+
forms off-white ppt and Cu2+ forms blue ppt.
The rest form white ppt.
D) mixture of acid and M2+ ions. So
observations B + observations for C
E) mixture of M3+ and M2+ ions (another ppt
due to M2+ is produced only after all the acidic
M3+ ions have reacted). So, observations is a
combination of A, B, then C.
, 2. Add carbonate then heat A) NH3 gas formed. NH4+
B) Carbonates may also form and decompose.
Observation for CuCO3:
Blue ppt formed, turned black on heating, CO2
gas
CuCO3
3 Add dilute H2SO4 White ppt (calcium sulfate) formed if test
solution contains high [Ca2+]. OR could be
Ba2+ (barium sulfate)
3.2 Maybe: then H2O2 Could test for Fe2+ or halide ions, basically
things that may be oxidised. Everytime you see
H2O2, you know H2O2 is an oxidising agent.
For example, Fe2+ is oxidised to Fe3+ (green to
brown solution). Halide ions like Cl- oxidised to
form Cl2 gas (blue litmus paper turns red and is
bleached)
4. Add NaOH, and then in excess Test for cations. (Note that there may be more
than one cation, so more than one ppt)
Most cations form white ppt with NaOH, you can
see that in the data booklet. Here are the
exceptions:
Mn2+:
Colourless solution
Off-white ppt formed. Insoluble in excess NaOH
(aq). Off-white ppt rapidly turned brown on
contact with air.
For Fe2+ :
Colourless solution. Green ppt formed, insoluble
in excess NaOH(aq). Green ppt turned brown
on contact with air.
You can use this set of notes for revision. It builds on basic QA knowledge from the A
level data booklet that is provided for you during theory/practical exams.
It would be ideal to memorise such that you can look at the left column of test and be
able to think of what are the possible outcomes, what could you be testing for. This will
help you greatly in QA practical exams and theory exams.
Tests Possibilities
Cations
1. Add carbonate A) Acidic high charge cation
Al3+, Cr3+, Fe3+: white/grey-green/reddish
brown ppt formed, ppt insoluble in excess, CO2
gas (colourless gas forms white ppt with
limewater)
B) acid: CO2 gas (colourless gas forms white
ppt with limewater)
C) carbonate ppt only. (Ba2+, Ag+, Ca2+, Zn2+,
Mg2+, Mn2+, Cu2+, Fe2+). Note that for Fe2+,
green ppt turns brown on contact with air. Mn2+
forms off-white ppt and Cu2+ forms blue ppt.
The rest form white ppt.
D) mixture of acid and M2+ ions. So
observations B + observations for C
E) mixture of M3+ and M2+ ions (another ppt
due to M2+ is produced only after all the acidic
M3+ ions have reacted). So, observations is a
combination of A, B, then C.
, 2. Add carbonate then heat A) NH3 gas formed. NH4+
B) Carbonates may also form and decompose.
Observation for CuCO3:
Blue ppt formed, turned black on heating, CO2
gas
CuCO3
3 Add dilute H2SO4 White ppt (calcium sulfate) formed if test
solution contains high [Ca2+]. OR could be
Ba2+ (barium sulfate)
3.2 Maybe: then H2O2 Could test for Fe2+ or halide ions, basically
things that may be oxidised. Everytime you see
H2O2, you know H2O2 is an oxidising agent.
For example, Fe2+ is oxidised to Fe3+ (green to
brown solution). Halide ions like Cl- oxidised to
form Cl2 gas (blue litmus paper turns red and is
bleached)
4. Add NaOH, and then in excess Test for cations. (Note that there may be more
than one cation, so more than one ppt)
Most cations form white ppt with NaOH, you can
see that in the data booklet. Here are the
exceptions:
Mn2+:
Colourless solution
Off-white ppt formed. Insoluble in excess NaOH
(aq). Off-white ppt rapidly turned brown on
contact with air.
For Fe2+ :
Colourless solution. Green ppt formed, insoluble
in excess NaOH(aq). Green ppt turned brown
on contact with air.
