25 min
START!
60 min
35 min
Question 1 (Practical)
Question 1 (Calculations)
Question 2 (Practical)
105 min
70 min
Question 2 (Calculations)
Question 3 (Q.A.)
Review/Reflection
120 min
Unknown
MCO3
Na2SO3.xH2O
[Analyte]
Ar , Mr
TITRIMETRY
GRAVIMETRY
CALORIMETRY
TITRIMETRY (TITRATION)
• Analytical method by which the concentration of an analyte (substance of unknown
concentration) is determined based on its stoichiometric reaction with a reagent of
known concentration (titrant) introduced to a sample gradually until the analyte is
consumed quantitatively.
• There are three main types of titrations in the CIE curriculum.
1. Acid – Base titration
2. Redox titration
3. Salt – Acid/Base Titration (includes hydrated salts & backward/indirect titrations )
APPARATUS (TITRATION)
Indicator
Weighing boat
Conical
Flask
Burette
Volumetric
Pipette
(25cm3)
Funnel
Volumetric
Flask
Beaker
Wash bottle
(dH2O)
Measuring
cylinder
APPARATUS (TITRATION)
White tile
Weighing balance
Stand & Clamp
Dropping pipette
Pipette pump
TITRATION SET-UP
make sure the jet space in the
burette is filled with the solution
and air bubbles are removed.
TITRATION PROCEDURE
1. Preparing the burette
2. Preparing the conical flask
3. Rough Titration
4. Accurate titrations
5. Calculations
TITRATION PROCEDURE
1. Preparing the burette
(i) Rinse the burette with titrant.
TITRATION PROCEDURE
1. Preparing the burette
(ii) Fill the burette with the titrant.
Funnel
Titrant
(iii) Remove the funnel
Burette
Ensure the tap is closed
& jet has no air bubbles.
TITRATION PROCEDURE
1. Preparing the burette
(iv) Record the initial burette reading
When reading a burette you must always view it at eye level, so
that you accurately record the level of the lowest point of the
solution’s meniscus
There is no need to adjust
the volume of the solution
to exactly 0.00 cm3.
TITRATION PROCEDURE
2. Preparing the conical flask
(i) Rinse pipette with analyte
TITRATION PROCEDURE
2. Preparing the conical flask
(ii) Transfer analyte to the conical flask using the pipette
TITRATION PROCEDURE
2. Preparing the conical flask
(ii) Transfer analyte to the conical flask using the pipette
There will be a very small amount of
solution in the end of the pipette.
Do not add this small drop of solution!
The pipette is calibrated to deliver the
exact volume with this drop remaining in
the pipette.
TITRATION PROCEDURE
2. Preparing the conical flask
(ii) Transfer analyte to the conical flask using the pipette
The calibration mark is aligned with the
lowest point of the meniscus
TITRATION PROCEDURE
2. Preparing the conical flask
(iii) Add few drops of indicator
2 to 3 drops
TITRATION PROCEDURE
3. Rough Titration
(i) Deliver the titrant into the conical flask until end point is reached
TITRATION PROCEDURE
End Point
TITRATION PROCEDURE
TITRATION PROCEDURE
3. Rough Titration
(ii) Record the final burette reading
The burette readings should always be given to 2dp
either ending in 0.00 or 0.05. If the bottom of the
meniscus sits on a line it should end with a 0.00. If the
meniscus sits between two lines it should end with 0.05.
Wash out the conical flask with plenty of tap water and then
rinse with distilled water ready for your second titration
TITRATION PROCEDURE
3. Rough Titration
(iii) Calculate the volume of titrant delivered
Initial burette reading (cm3)
Final burette reading (cm3)
Titre (cm3)
TITRATION PROCEDURE
1
2
3
4
TITRATION PROCEDURE
4. Accurate Titrations
(i)
Repeat the titrations until you achieve at least 2 concordant results
• lf 2 or 3 titre values are within 0.10cm3 (concordant) then we can say results are
accurate.
• Close to the endpoint of the titration (approx. 2cm3 before the rough titre) you might like to
add only part of a drop; this is possible by allowing half of a drop to come out of the
burette and with the help of your wash-bottle you can rinse it into your flask
• It is also good practice to wash down the inside walls of your conical flask again once you
have reached the end-point
TITRATION PROCEDURE
4. Accurate Titrations
Distilled water can be added to the conical flask during a titration
to wash the sides of the flask so that all the acid on the side is
washed into the reaction mixture to react with the alkali. It does
not affect the titration reading as water does not react with the
reagents or change the number of moles of acid added.
ACCURATE TITRATION RESULTS
Trial
Initial burette reading (cm3)
Final burette reading (cm3)
Titre (cm3)
1
0.50
24.50
24.00
2
2.50
27.00
24.50
3
1.55
25.95
24.40
24.50 + 24.40
Average Titre =
= 24.45
2
24.45 cm3 of titrant.
25.0cm3 of analyte required ..............................
TITRATION CALCULATIONS
Vtitrant (in cm3)
24.45
=c×
ntitrant = c ×
1000
1000
T + 2A → TA2
nanalyte = 2 × ntitrant
1. Calculate the number of moles of titrant
2. Use the stoichiometric equation to calculate the number
of moles of the analyte
3. Use the number of moles of the analyte to find the unknown.
TITRATION MARK ALLOCATION [14 – 18]
Rough Titre (1 mark)
• two burette readings for the rough titration
• titre for rough titration
Accurate Titres (3 marks)
• initial / start and (burette) reading / volume
• final / end and (burette) reading / volume
• titre or volume / of FA used / added
• unit: / cm3 or (cm3)
• All accurate burette readings are recorded to the nearest 0.05 cm3
• The final accurate titre recorded is within 0.10 cm3 of any other
accurate titre
TITRATION MARK ALLOCATION
Accuracy (3 marks)
δ ⩽ 0.20 cm3 (3)
0.20 cm3 < δ ⩽ 0.40 cm3 (2)
0.40 cm3 < δ ⩽ 0.60 cm3 (1)
Calculations (7 marks)
• Average Titre
• Number of moles
• Concentration
• Unknown
δ is the difference between the
candidate’s mean titre vs the
supervisor’s mean titre
REDOX TITRATION
• Redox titration is based on an oxidation-reduction reaction between the titrant and the
analyte.
• It is one of the most common laboratory methods to identify the concentration of
unknown analytes.
• A redox titration usually does not require an indicator.
• The most important redox titrations are:
1. Permanganometric
2. Iodometric
PERMANGANOMETRY
• Involves the use of KMnO4 (Potassium Manganate (VII)) as the oxidising agent.
• KMnO4 is used as a standard solution/titrant and is an auto - indicator
• The end point of the titration involves the occurrence or disappearance of the pink
purple colour
• Involves an acidic medium (H+)
MnO4 − + 8 H+ + 5 e− → Mn2+ + 4 H2O
purple
colourless
PERMANGANOMETRY (9701 F/M P33 2020 Q1)
Titration of Hydrogen Peroxide (H2O2) with KMnO4
0.0300 mol/dm3 KMnO4
(FA 1)
25 cm3 of
Diluted H2O2
(FA4)
H 2 O2 + H +
20 cm3 of
H2SO4
(FA2)
1
2
3
IODOMETRY
• In an iodometric titration, an oxidising agent is allowed to react with an
excess of Potassium iodide to liberate free iodine.
• It is an indirect titration.
• The free iodine is titrated against a standard reducing agent.
• Usually, a standard thiosulphate solution is used e.g. Na2S2O3.
IODOMETRY
• The first step involves the reaction between the oxidising agent and excess
Potassium iodide (KI).
• Thus, iodine is quickly liberated.
KI + Oxidising Agent → I2
• The liberated iodine is titrated with a standard solution of sodium
thiosulphate.
• Starch is used as an indicator.
IODOMETRY
• At the end point, all of the iodine will react with thiosulphate and produce
iodide ions.
• Therefore, the blue colour of starch indicator disappears.
• Iodometric titrations occur in an acidic medium.
IODOMETRY (9701 M/J P33 2021 Q1)
Determining the concentration of sodium
chlorate(I) in a sample of bleach
25 cm3 of
Diluted Bleach
(FA2)
20 cm3 of
Dil. H2SO4
(FA3)
I2
2
15 cm3 of
KI
(FA4)
1
3
0.100 mol/dm3
Na2S2O3 (FA5)
4
IODOMETRY
10 drops of starch
indicator
0.100 mol/dm3
Na2S2O3
0.100 mol/dm3
Na2S2O3
6
7
Yellow
STOP!
5
I2
Blue - black
6
STOP!
8
Colourless
BACK TITRATION
• A back titration is a titration method where the concentration/unknown of an analyte is
determined by reacting it with a known amount of excess reagent.
• The remaining excess reagent is then titrated with another, second reagent.
• The titration results would show how much of the excess reagent was used in the first
titration, thus allowing the original analyte's concentration/unknown to be calculated.
• A back titration may also be called an indirect titration.
BACK TITRATION
• A group 2 carbonate, XCO3 is insoluble in water. However, it can react with excess
hydrochloric acid
XCO3 + 2HCl → XCl2 + CO2 + H2O
• Therefore, we can perform a back titration to find the unknown (X).
• The remaining excess HCl can be titrated with a known concentration of NaOH to
determine the number of moles of the excess acid.
NaOH + HCl → NaCl + H2O
The number of moles of acid can be used to calculate the moles which reacted w XCO3.
BACK TITRATION
Weighing boat
0.71 g
20 cm3 of 1 mol/dm3 HCl
= XCO3
Mean Titre was 12.00 cm3
0.500 mol/dm3 NaOH
What is the identity of X?
Excess HCl
BACK TITRATION (CALCULATIONS)
n(NaOH)= c(NaOH) x V(NaOH) = 0.500 mol/dm3 x 12/1000 dm3 = 0.006 mol
excess n(HCl) = n(NaOH) = 0.006 mol
(HCl : NaOH = 1 : 1)
n(HCl) that reacted with carbonate = n(HCl) added - excess n(HCl)
= 0.02 mol – 0.006 mol = 0.014 mol
n(XCO3) = 1/2 x n(HCl) that reacted with carbonate
= 1/2 x 0.014 = 0.007 mol
Mr = m(XCO3) / n(XCO3) = 0.71g / 0.007 mol = 101.4 g/mol
Ar(X) = Mr(XCO3) - Ar(C) - 3Ar(O) = 101.4 – 12 – 3(16) = 41.4 g/mol
X = Ca
STANDARD SOLUTION
• A standard solution is one that has a known concentration.
• With a standard solution, it is possible to investigate the concentration of other solutions of
unknown concentration by titration.
• A standard solution is made by dissolving an accurate mass of solute into a known
volume of water.
STANDARD SOLUTION (PROCEDURE)
1. Use the weighing boat to weigh out the required amount of solute. Empty it into 250
cm3 beaker.
To ensure there is no solute remaining in the weighing boat, wash the weighing boat twice
using distilled water from a wash bottle and pour the washings into the beaker
Weighing boat
____g
= solute
Weighing boat
with residual solute
Beaker
Wash bottle
with dH2O
STANDARD SOLUTION (PROCEDURE)
2. Add more water to the beaker so that you have about 100 cm3. Stir the mixture with the
stirring rod until all the solute has dissolved.
Stirring rod
Beaker
Solute completely dissolves
STANDARD SOLUTION (PROCEDURE)
3. Place the filter funnel into the neck of the 250 cm3 volumetric flask and pour the
contents of the beaker into the flask.
Funnel
Dissolved solute
Calibration mark
250 ml
Volumetric flask
250 ml
STANDARD SOLUTION (PROCEDURE)
4. Using a wash bottle, rinse the beaker and pour the washings into the volumetric flask.
Repeat this several times. You must also rinse the stirring rod.
Washings
Beaker with residual
solution
Dissolved solute
Stirring rod
STANDARD SOLUTION (PROCEDURE)
5. When the level of the liquid is just a few cm3 below the mark on the neck of the
volumetric flask, take the dropper and with great care use it to add distilled water from
the wash bottle to the solution one drop at a time until the lowest point of the meniscus is
touching the line
NB
If you go over the mark and the
level of the liquid is above the line
then you must reweigh your solute
and repeat the preparation of the
solution.
STANDARD SOLUTION (PROCEDURE)
6. Place the stopper in the neck of the volumetric flask and, keeping the stopper firmly in
the neck using your thumb, mix the solution by turning the flask upside down at least five
or six times.
The solution is now ready
for titration
DILUTION BEFORE TITRATION
• When using a concentrated original sample, it may be necessary to dilute the sample
before titrating.
• The reason for this is that it would take more volume than an be held in the burette to
reach the end point.
• Dilution involves a pipette/burette and a volumetric flask
DILUTION BEFORE TITRATION (9701 F/M P33 2020 Q1)
Scenario 1 (Pipette & Volumetric Flask)
1
25 cm3 of
Hydrogen Peroxide
(FA3)
250 cm3
Volumetric Flask
2
Distilled water
n=cxV
n = constant
c = decreases
V = increases
DILUTION BEFORE TITRATION
3
4
25 cm3 of
Diluted H2O2
(FA4)
Transfer FA4 to
beaker
Beaker with FA4
FA4
Diluted hydrogen
peroxide
5
DILUTION BEFORE TITRATION (9701 O/N P32 2008 Q1)
Scenario 2 (Burette & Volumetric Flask)
1
Btwn 41.00 & 42.00 cm3 FB2
(KMnO4)
250 cm3
Volumetric Flask
2
Distilled water
n=cxV
n = constant
c = decreases
V = increases
DILUTION BEFORE TITRATION
3
4
5
25 cm3 of
Diluted KMnO4
(FB5)
Transfer FB5 to
beaker
Beaker with FB5
FB5
Diluted KMnO4
10 cm3 of KI
+
10 cm3 of H+
THERMOMETRIC TITRATION
• In a thermometric titration, the titrant is added at a known constant rate to an analyte
until the completion of the reaction is indicated by a change in temperature.
• The temperature is measured for each portion of analyte is added.
• A graph of temperature against volume of titrant delivered is plotted in order to find the
endpoint of the titration (the point where there is maximum or minimum temperature).
• The volume of the titrant is used to calculate the unknown concentration of the analyte.
THERMOMETRIC TITRATION (9701 F/M P33 2022 Q1)
1
2
Plastic cup
25 cm3 of
NaOH
(FA1)
Beaker
4
H2SO4 (FA2)
(5 cm3 increments)
3
Thermometer
Thermometer
1.90M NaOH
1.90M NaOH
THERMOMETRIC TITRATION
Volume of FA2 added / cm3
0
5
10
15
20
25
30
35
40
45
50
Temperature / °C
25.0
25.8
27.0
28.0
28.8
29.8
30.2
30.0
29.9
30.1
29.8
Endpoint
•
•
•
•
Axes
Scale
Plotted points
Lines of best fit
A
sulphuric
27 cm3 of sulfuric
acid, FA 2, required to
neutralise 25.0 cm3 of
sodium hydroxide, FA 1.
CALCULATING PERCENTAGE ERROR
• There are several reasons why the final value you record during an experiment may
be inaccurate.
• Some of the errors associated with a value may be random (e.g. the substances used
may be impure).
• More commonly though, errors are systematic and are associated with the apparatus
used.
• For every experiment you complete you must assess and state the total percentage error
associated with the values you report.
CALCULATING PERCENTAGE ERROR
• In some circumstances you can check what the actual value should be. If you know this
value then you can calculate the experimental error using the formula:
Actual value – Experimental Value
× 100
Percentage error =
Actual value
CALCULATING PERCENTAGE ERROR
Each type of apparatus has a sensitivity/maximum/total error/uncertainty
• balance ± 0.005 g (2dp)
• volumetric flask ± 0.1 cm3
• 25 cm3 pipette ± 0.1 cm3
• burette ± 0.05 cm3
• Thermometer ± 0.5°C
• The sensitivity/total error can be used to calculate percentage error
CALCULATING PERCENTAGE ERROR (BURETTE)
• Burettes used in schools commonly read to ± 0.05 cm3.
• If you take two burette readings in a titration, then each of them has an error of ±0.05
cm3 and the total error is 0.10 cm3.
• If you run in 22.00 cm3 of solution from the burette (titre),
Total error
0.10
Percentage error =
× 100 =
× 100% = 0.45%
Value of measurement
22
CALCULATING PERCENTAGE ERROR
• To decrease the apparatus errors you can either decrease the sensitivity error by using
apparatus with a greater resolution (finer scale divisions ) or you can increase the size
of the measurement made.
• In order to reduce errors in a titration, replacing measuring cylinders with pipettes or
burettes which have lower apparatus sensitivity error will lower the error
• To reduce the error in a burette reading it is necessary to make the titre a larger
volume.
• This could be done by: increasing the volume and concentration of the substance in the
conical flask or by decreasing the concentration of the substance in the burette.
GRAVIMETRY
• Gravimetric analysis is a technique through which the amount of an analyte can be
determined through the measurement of mass.
• The quantity/unknown of the analyte is determined based on the mass of the solid.
• An example would be using heat to decompose a compound to give solid residue and
gaseous product (resulting in change in mass), and the difference in mass before/after
heating to account for mass lost.
APPARATUS (GRAVIMETRY)
Spatula
Electronic balance
Crucible with lid
Pipe – clay triangle
Crucible tongs
Tripod Stand
Bunsen burner
Heat proof mat
SET-UP (GRAVIMETRY)
Crucible tongs
Gas supply
Crucible
Pipe – clay triangle
Tripod stand
Bunsen burner
BUNSEN BURNER (GRAVIMETRY)
GRAVIMETRY
Volatisation Gravimetry
THERMAL DECOMPOSITION
Metal Nitrates
MNO3/M(NO3)2
Metal Carbonates /
Hydrogencarbonates
XCO3/X2CO3/XHCO3
Metal Hydroxide
MOH/M(OH)2
Hydrated Salts
e.g MgSO4.xH2O
Hydrated Basic Metal
Carbonates
e.g. CuCO3.Cu(OH)2.xH2O
GRAVIMETRY
Cover the crucible with the lid if there is
spitting/frothing during heating.
Gas evolved upon heating
Residue
Powdered solid
Mass Loss = Mass of powdered solid – Mass of residue
GRAVIMETRY (9701 F/M P33 2019 Q2)
Basic Copper(II) Carbonate (FA3)
Empty crucible + lid
____g
crucible(open)
Crucible + lid + FA3
____g
Pipe – clay triangle
Tripod stand
Crucible(lid)
GRAVIMETRY (9701 F/M P33 2019 Q2)
Basic Copper(II) Carbonate (FA3)
Empty crucible + lid
____g
spatula
crucible(open)
Crucible + lid + FA3
____g
Pipe – clay triangle
Tripod stand
Crucible(lid)
GRAVIMETRY
____g
Pipe – clay triangle
Crucible +
lid + residue
Tripod stand
Crucible(open) with FA3
FA3
05:00
Heat Gently: 1 min
Heat Strongly: 4 min
Crucible + lid + residue
COOLING!
Heat-proof
mat
The lid is replaced during cooling to
prevent the absorption of water vapour
from the atmosphere.
GRAVIMETRY
Mass of crucible + lid (g)
Mass of crucible + lid + FA3 (g)
Mass of crucible + lid + residue (g)
Mass of FA3 (g)
Mass of residue (g)
Mass Loss (g)
•
•
•
•
Layout [1]
Headings + units [1]
Correct subtractions + dp [1]
Accuracy [3]
37.88
40.23
39.69
2.35
1.81
0.54
GRAVIMETRY (9701 O/N P31 2008 Q2)
Empty boiling tube
Empty beaker
____g
____g
Press the tare button
Hydrated
MgSO4
(FA4)
Boiling tube + FA4
____g
GRAVIMETRY (9701 O/N P31 2008 Q2)
Heat – proof mat
Test tube holder
COOLING!
Boiling tube + residue
____g
GRAVIMETRY
Mass of empty tube (g)
Mass of tube + FA4 (g)
Mass of tube + residue (g) after first heating
Mass of tube + residue (g) after second heating
Mass of FA4 (g)
Mass of residue (g)
Mass of water lost (g)
•
•
•
•
Layout [1]
Headings + units [1]
Correct subtractions + dp [1]
Accuracy [2]
42.63
44.98
43.93
43.82
2.35
1.19
1.16
GRAVIMETRY (9701 M/J P31 2021 Q2)
Hydrated MZ (FA4)
Empty crucible + lid
spatula
____g
crucible(open)
Between 2.40g & 2.60g FA4
Crucible + lid + FA4
____g
Pipe – clay triangle
Tripod stand
Crucible(lid)
GRAVIMETRY
____g
Pipe – clay triangle
Crucible +
lid + residue
Tripod stand
Crucible(open) with FA4
FA4
05:00
Heat Gently: 1 min
Heat Strongly: 4 min
Crucible + lid + residue
COOLING!
Heat-proof
mat
The lid is replaced during cooling to
prevent the absorption of water vapour
from the atmosphere.
SOURCES OF ERROR & IMPROVEMENT
Errors
Sample/Analyte has not completely decomposed.
Improvements
Heat to a constant mass.
Use a larger initial mass of analyte (FA?).
Use a balance that reads more dp.
Use a desiccator for cooling.
Repeat the experiment to obtain concordant/consistent results
CALCULATING % ERROR
• The accuracy of a two-decimal place balance is ±0.005 g.
• Each reading has this error and if you make two readings then the
maximum error is ±0.01 g. Consider the following example:
Mass of crucible + lid = 39.10 g; maximum error = 0.005g
Mass of crucible + lid + solid = 40.55 g; maximum error = 0.005g
Mass of solid = 1.45 g; maximum error = 0.01g
maximum error
0.01
% error =
×100 =
×100 = 0.69%
value of measurement
1.45
CALORIMETRY
• A technique used to measure the amount of heat released/absorbed by
a chemical reaction.
• The heat evolved by the chemical reaction is determined using a
calorimeter.
• The transfer of heat or flow of heat is expressed as the enthalpy
change, ∆H.
CALORIMETER (SIMPLE)
Plastic cup
Thermometer
For an exothermic rxn
• Heat lost by rxn = Heat gained by water
For an endothermic rxn
• Heat gained by rxn = Heat lost by water
Reaction mixture
q = mc∆T
q = heat energy (J)
∆H = Enthalpy change (kJ/mol)
m = mass of water (g)
c = specific heat capacity of water
∆T = Temperature change (T2 – T1)
n = number of moles of limiting reactant
∆H =
−q
n
CALORIMETRY APPARATUS
Plastic cup
Stopclock
Thermometer
Measuring cylinder
Electronic balance
Beaker
Spatula
Burette
TEMPERATURE – TIME GRAPH (EXTRAPOLATION)
∆T = T2 – T1
TEMPERATURE – VOLUME GRAPH (EXTRAPOLATION)
∆T = Tmax – Tinitial
ο
Temperature ( C)
Tmax
Tinitial
Vendpoint
Volume of titrant added (cm3)
CALORIMETRY (SCENARIOS)
• SCENARIO 1: Two aqueous solutions e.g. Neutralisation reaction
• SCENARIO 2: Solid Added to an aqueous solution e.g. Displacement
reaction, Dissolution (Dissolving a solid in aqueous solution).
• SCENARIO 3: Decomposition or Combustion Reaction
∆Hreaction
∆Hneut
∆Hdisplacement
HESS’s LAW
∆Hsolution
∆Hcomb
CALORIMETRY (CALCULATIONS)
Temperature vs Time/Volume Added
B
A
Determine ∆T
Calculate Heat Transferred
q = mc∆T
n=c×V=
m
M
Calculate moles of
limiting reagent
Calculate ∆H
q
mc∆T
−
or −
n
n
CALORIMETRY (9701 M/J P32 2021 Q2)
Impure Na2CO3 (FB3)
Plastic cup
spatula
____g
____g
FB3 +
plastic cup
Btwn 1.9g & 2.1g FB3
Plastic cup
Beaker
Twater
25cm3
dH2O
CALORIMETRY (9701 M/J P32 2021 Q2)
Stirring rod
Distilled water
FB3
Record highest
temp. reached
Experiment 2
Repeat using btwn 3.9g & 4.1g of FB3
CALORIMETRY (9701 M/J P32 2021 Q2)
Experiment 1
Mass of empty cup / g
Mass of cup + FB3 / g
Mass of FB3 / g
Initial Temperature / °C
Maximum Temperature / °C
Temperature change / °C
CALORIMETRY (9701 M/J P34 2021 Q2)
Experiment 1
Plastic cup
Beaker
30cm3
FB6 (NH3(aq))
Tmax
a
Tinitial
b
∆T
Tinitial
25cm3
FB7 (HCl(aq))
FB6
STIR!
a–b
Tmax
CALORIMETRY (9701 M/J P34 2021 Q2)
Experiment 1
Initial Temperature / °C
Maximum Temperature / °C
Temperature change / °C
CALORIMETRY (9701 M/J P34 2021 Q2)
Experiment 2
30cm3
distilled
water
Plastic cup
Beaker
Tip all FB8
Tinitial
diH2O
____g
Container +
FB8 (NH4Cl(s))
STIR!
CALORIMETRY (9701 M/J P34 2021 Q2)
Experiment 2
Tmin
____g
Initial Temperature / °C
Minimum Temperature / °C
Temperature change / °C
Mass of container + FB8 / g
Mass of container + residual FB8 / g
Mass of FB8 added / g
Container +
residual FB8
CALORIMETRY (9701 M/J P32 2020 Q2)
Plastic cup
20cm3
distilled
water
Beaker
Tip all FB5
____g
Container +
FB5
(hydrated
Na2S2O3)
Tinitial
diH2O
STIR!
CALORIMETRY (9701 M/J P32 2020 Q2)
Tmin
____g
Initial Temperature / °C
Minimum Temperature / °C
Temperature change / °C
Mass of container + FB5 / g
Mass of container + residual FB5 / g
Mass of FB5 added / g
Container +
residual FB5
CALORIMETRY (9701 O/N P35 2018 Q1)
____g
Plastic cup
Container +
FA1 impure
Na2CO3
Beaker
25cm3 of HCl
(FA2)
Tminutes
FA2
00:00
Measure T
every 30s / half min
Tip all FA1
02:30
t = 2.5 min
CALORIMETRY (9701 O/N P35 2018 Q1)
t = 3 min
03:00
03:30
Measure t
every 30s /
half min
interval
09:00
STOP!
____g
Container +
residual FA2
04:00
CALORIMETRY (9701 O/N P35 2018 Q1)
Time / min
0
0.5
1.0
1.5
2.0
2.5
Temperature / °C
Time / min
3.0
3.5
4.0
4.5
8.5
9.0
x
5.0
5.5
6.0
6.5
Temperature / °C
Mass of container + FA1 / g
Mass of container + residual FA1 / g
Mass of FA1 added / g
7.0
7.5
8.0
CALORIMETRY (9701 O/N P35 2018 Q1)
Choose a scale that allows
you to plot 2 or 10 °C above
the maximum temperature
reached
o
Temperature ( C)
T2
∆T
T1
2.5
Time (min)
CALORIMETRY (9701 M/J P34 2022 Q2)
Plastic cup
Beaker
Tinitial
FB3
(NaOH)
Burette 1
10cm3 FB3
9.0 cm3
Distilled
water
Distilled
water
FB4 (HCl)
Burette 2
1.0 cm3
FB4
Expt 1
CALORIMETRY (9701 M/J P34 2022 Q2)
Tmax
mixture
STIR!
Repeat…
Expt
Vol FB3
(cm3)
Vol H2O
(cm3)
Vol FB4
(cm3)
1
10.00
9.00
1.00
2
10.00
7.00
3.00
3
10.00
5.00
5.00
4
10.00
3.00
7.00
5
10.00
1.00
9.00
6
10.00
0.50
9.50
7
10.00
0.25
9.75
Tmax
Maximum
CALORIMETRY (9701 M/J P34 2022 Q2)
VFB4 that
reacts with
10cm3 FB3
Volume FB4 used (cm3)
CALORIMETRY (ASSUMPTIONS)
• There is no/negligible heat transfer between the environment & the
calorimeter.
• The calorimeter does not absorb energy.
• All dilute aqueous solutions are assumed to have the same density &
specific heat capacity equal to water
m = Total volume of solution(s)
CALORIMETRY (SOURCES OF ERROR)
• Heat Loss to the surroundings
• Uncertainty in temperature measurement
• Uncertainty in mass measurement
• Improper mixing of reactants
IMPROVEMENTS
• Use a lid to cover the plastic cup
• Use a magnetic stirrer
• Use a digital lab thermometer
• Use a balance with more dp
• Insulate the outer walls of the plastic cup
• Use larger volumes of solutions
• Taking more readings
CALORIMETRY (PERCENTAGE ERROR)
• Given that ∆T = 3.5 °C , what is the maximum percentage error?
2×0.5
Percentage Error =
× 100 = 28.6%
3.5
• The greater the value of ∆T, the smaller the percentage error.
CALORIMETRY (PERCENTAGE ERROR)
• The theoretical value for the enthalpy of neutralisation for a particular
reaction is -57.6 kJ/mol.
• Given that the experimental value for ∆Hneut you got is -48.7 kJ/mol,
calculate the percentage error.
−57.6−(−48.7)
% error =
× 100 = 15.45%
−57.6
RATE OF REACTION
• CIE usually asks questions involving the effect of concentration on the
rate of reaction.
• These questions also involve dilution with distilled water.
• The main experiments involved are:
1. The Disappearing cross experiment (Acid added to thiosulphate solution)
2. The iodine clock experiment
DISAPPEARING CROSS EXPERIMENT
• A simple experiment which can be done to determine how rate of reaction
is affected by concentration is the disappearing cross experiment.
• This experiment can be done for a number of different reactions, but
taking the following reaction as an example:
Na2S2O3 (aq) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + SO2 (g) + S (s)
• In this reaction, sodium thiosulphate reacts with hydrochloric acid
• The key product which allows this experiment to work, is the sulfur which is
a solid, and causes the solution to become opaque.
DISAPPEARING CROSS EXPERIMENT
DISAPPEARING CROSS EXPERIMENT
Before reaction
After reaction
STOP!
DISAPPEARING CROSS EXPERIMENT
• There are actually two factors which can be investigated using the
disappearing cross reaction:
1. Changing the temperature
2. Changing the concentration of the HCl or the thiosulfate
• You can plot graph for Rate of reaction against concentration to determine
the effect of concentration on the rate of reaction.
DISAPPEARING CROSS EXPERIMENT
(Rate is) proportional
(to conc of thiosulfate)
DISAPPEARING CROSS EXPT (9701 O/N P34 2021 Q1)
EXPERIMENT 1
FB1
45cm3 FB1
(Na2S2O3)
100cm3
beaker
Cross beneath
the beaker.
10cm3 FB2
(HCl)
FB1
00:00
START!
Cross disappears
00:00
STOP!
DISAPPEARING CROSS EXPT (9701 O/N P34 2021 Q1)
EXPERIMENT 2
Second
Burette
20cm3 FB1
(Na2S2O3)
10cm3 FB2
(HCl)
25cm3
distilled
water
100cm3
beaker
Diluted FB1
FB1
Cross beneath
the beaker.
00:00
START!
Cross disappears
00:00
STOP!
DISAPPEARING CROSS EXPT (9701 O/N P34 2021 Q1)
Expt
Vol FB1 (cm3)
Vol Water
(cm3)
Vol FB2 (cm3)
1
45.00
0.00
10.00
2
20.00
25.00
10.00
3
25.00
20.00
10.00
4
30.00
15.00
10.00
5
35.00
10.00
10.00
Rate
Time (s)
Rate
1000
Rate =
Reaction time
Vol FB1 (cm3)
DISAPPEARING CROSS EXPT (9701 O/N P31 2020 Q2)
EXPERIMENT 1
20cm3 FA4
(HCl)
40cm3 FA5
(Na2S2O3)
00:00
FA5
START!
Cross beneath
the beaker.
Cross disappears
00:00
STOP!
DISAPPEARING CROSS EXPT (9701 O/N P31 2020 Q2)
EXPERIMENT 2
20cm3 FA4
(HCl)
20cm3 FA5 (Na2S2O3) +
20cm3 distilled water
00:00
FA5
START!
Cross beneath
the beaker.
Cross disappears
00:00
STOP!
DISAPPEARING CROSS EXPT (9701 O/N P31 2020 Q2)
Expt
Vol FA5 (cm3)
Vol Water
(cm3)
Vol FA4 (cm3)
1
40.00
0.00
20.00
2
20.00
20.00
20.00
Time (s)
Rate
IODINE CLOCK EXPERIMENT
• In the iodine clock reaction, there are two processes happening
simultaneously. The first step is a slow reaction producing iodine:
Oxidising Agent + I- → I2
• The iodide ions come from Potassium Iodide (KI).
• However, the iodine is never seen initially because of the very fast second
reaction in which it is immediately reduced to colourless iodide ions by
thiosulfate ions.
IODINE CLOCK EXPERIMENT
I2 + 2S2O32- → 2I- + S4O62• Thus, iodine is slowly formed and the instantly converted back to iodide
ions until a the thiosulfate ions are all used up.
• The thiosulfate is a limiting reagent.
• As the thiosulfate gets used up, the iodine concentration shoots up and the
intense blue-black colour of the starch-iodine complex appears.
Iodine + Starch → Blue - black
IODINE CLOCK EXPERIMENT
IODINE CLOCK EXPERIMENT (9701 O/N P36 2018 Q1)
EXPERIMENT 1
20cm3 FB1
(FeCl3)
100cm3
beaker
20cm3 FB3
(Na2S2O3)
10cm3
FB2
(KI)
Second
beaker
FB2
IODINE CLOCK EXPERIMENT (9701 O/N P36 2018 Q1)
EXPERIMENT 1
10cm3 FB4
(starch indicator)
00:00
FB1
FB2 + FB3
FB2 + FB3 + FB4
00:00
STOP!
START!
STIR!
Blue black
IODINE CLOCK EXPERIMENT (9701 O/N P36 2018 Q1)
EXPERIMENT 2
Second
Burette
10cm3 FB1
(FeCl3)
100cm3
beaker
10cm3
distilled
water
FB1
10cm3 FB2
(KI)
Second
beaker
IODINE CLOCK EXPERIMENT (9701 O/N P36 2018 Q1)
EXPERIMENT 2
10cm3 FB4
(starch indicator)
20cm3 FB3
(Na2S2O3)
FB2 + FB3
FB2
00:00
00:00
STOP!
Diluted FB1
Blue black
START!
STIR!
FB2 + FB3 + FB4
IODINE CLOCK EXPERIMENT (9701 O/N P36 2018 Q1)
Expt
Vol FB1
(cm3)
Vol Water
(cm3)
Vol
FB2
(cm3)
Vol
Vol
FB3
FB4
(cm3) (cm3)
1
20.00
0.00
10.00
20.00 10.00
2
10.00
10.00
10.00
20.00 10.00
3
16.00
4.00
10.00
20.00 10.00
4
14.00
6.00
10.00
20.00 10.00
5
8.00
12.00
10.00
20.00 10.00
Rate
Time
(s)
Rate
1000
Rate =
Reaction time
Vol FB1 (cm3)
IODINE CLOCK EXPERIMENT (9701 M/J P35 2017 Q1)
EXPERIMENT 1
20cm3 FA1
(K2S2O8)
Beaker A
10cm3 FA3
(Na2S2O3)
20cm3 FA2
(KI)
Beaker B
FA2
IODINE CLOCK EXPERIMENT (9701 M/J P35 2017 Q1)
EXPERIMENT 1
10 drops of starch
indicator
00:00
FA1
START!
STIR!
FA2 + FA3 + starch indicator
FA2 + FA3
00:00
STOP!
Blue black
IODINE CLOCK EXPERIMENT (9701 M/J P35 2017 Q1)
EXPERIMENT 2
Second
Burette
10cm3 FA1
10cm3
distilled
water
Beaker A
FB1
20cm3 FA2
(KI)
Beaker B
IODINE CLOCK EXPERIMENT (9701 M/J P35 2017 Q1)
EXPERIMENT 2
10 drops of starch
indicator
00:00
10cm3 FA3
(Na2S2O3)
FA1
FA2
FA2 + FA3
00:00
STOP!
Blue black
START!
STIR!
FA2 + FA3
+ starch
indicator
IODINE CLOCK EXPERIMENT (9701 M/J P35 2017 Q1)
Expt
Vol FA1
(cm3)
Vol Water
(cm3)
1
20.00
0.00
2
10.00
10.00
3
15.00
5.00
4
12.00
8.00
5
8.00
12.00
Rate
Time
(s)
Rate
Time / rate related to
concentration
500
Rate =
Reaction time
Vol FB1 (cm3)
Measuring the volume of gas via Water Displacement
• The volume of gas generated in a chemical reaction is measured by
tracking the volume of water displaced from an inverted water-filled
measuring cylinder.
• The volume of water displaced is equal to the volume of gas produced.
• As the gas is produced in the reaction flask, it exits through the rubber
tubing and displaces the water in the measuring cylinder.
• This method is suitable for collecting gases which are insoluble or only
slightly soluble in water.
Measuring the volume of gas via Water Displacement
• As the gases cannot dissolve in water and are lighter in density than water,
they would rise to the top of the gas jar and be collected there.
• Some examples of gases collected via this way include H2, CO2 & CO2.
•
1.
2.
3.
Examples of reactions which produces these gases are:
Reaction of a solid metal carbonate with an acid.
Reaction of a metal with an acid
Decomposition of Hydrogen Peroxide catalysed by MnO2.
Measuring the volume of gas via Water Displacement
Bung
Rubber
Tubing
Measuring the volume of gas via Water Displacement
WATER DISPLACEMENT (9701 M/J P31 2019 Q1)
INVERT
Clamp
Tub with water
≈ 5cm
250cm3 measuring
cylinder filled with water
WATER DISPLACEMENT (9701 M/J P31 2019 Q1)
Bung
Clamp
Delivery tube to
measuring cylinder
FA1 (HCl)
Flask
____g
Container + FA2
(MCO3)
WATER DISPLACEMENT (9701 M/J P31 2019 Q1)
Tip all FA2
(FA1) HCl
WATER DISPLACEMENT (9701 M/J P31 2019 Q1)
Gas from flask
Vgas = V2 – V1
____g
Container +
residual FA2
WATER DISPLACEMENT (9701 M/J P31 2019 Q1)
Volume of gas (cm3)
Mass of container + FA2 (g)
Mass of container + residual FA2 (g)
Mass of FA2 added (g)
Vg × 10−3
ng =
24
n(MCO3) = n(CO2)
m
Mr =
n
Ar(M) = Mr – Ar(C) – 3Ar(O)
WATER DISPLACEMENT (9701 O/N P34 2019 Q1)
INVERT
Clamp
Tub with water
≈ 5cm
250cm3 measuring
cylinder filled with water
WATER DISPLACEMENT (9701 O/N P34 2019 Q1)
20cm3
distilled
water
30cm3 FB1
(H2O2)
X
Tip all FB2
(MnO2)
FB1
00:00
START!
WATER DISPLACEMENT (9701 O/N P34 2019 Q1)
01:00
Vol(O2) at t = 1 min
04:00
Vol(O2) at t = 4 min
WATER DISPLACEMENT (9701 O/N P34 2019 Q1)
Volume of Oxygen after 1 minute (cm3)
Volume of Oxygen after 4 minute (cm3)
WATER DISPLACEMENT (9701 M/J P32 2016 Q1)
INVERT
Clamp
Tub with water
≈ 5cm
250cm3 measuring
cylinder filled with water
WATER DISPLACEMENT (9701 M/J P32 2016 Q1)
Tip the FB1
25 cm3 of
FB2 (H2SO4)
Mg Ribbon (FB1)
____g
TARE!
FB2
WATER DISPLACEMENT (9701 M/J P32 2016 Q1)
Vol(H2) collected
WATER DISPLACEMENT (9701 M/J P32 2016 Q1)
Initial volume of gas (cm3)
Final volume of gas (cm3)
Volume of gas produced (cm3)
Mass of FB1 added (g)
0.00
QUALITATIVE ANALYSIS
• Qualitative analysis is a method used for identification of ions or
compounds in a sample.
• Deals with identification of various species (cations, anions and functional
groups etc) present in a mixture of species.
Perform the test(s)
Make observations
Make Deductions
1
2
3
PHYSICAL APPEARANCE & POSSIBLE IDENTITIES
COLOUR
White
Blue
Green
Golden yellow or Red brown or Brown
Black
Very pink (Not visible in soltn)
LIKELY COMPOUNDS
Ba2+,Ca2+, Al3+, Zn2+, Mg2+, NH4+ salts
Hydrated copper salts
Fe2+ salts, CuCl2, CuCO3 salts
Fe3+ salts
CuS, CuO, PbS, MnO2, FeS
Hydrated manganese salt
ACTION OF HEAT
• Heating a salt may cause it to decompose. The decomposition may result in:
(a) a colour change
(b) evolution of a gas
(c) liberation of water vapour
• Gases such as carbon dioxide, nitrogen dioxide, ammonia or oxygen can be
evolved.
• By identifying the gas or gases liberated, it is possible to pinpoint the anion
present in the salt.
ACTION OF HEAT
ACTION OF HEAT
1. Is residue present or not after heating
• Observe the colour of the residue when hot and cold
• If substances sublime and no residue is left, No heavy metal is present but
the salt potentially contains ammonium ions.
If residue left, Heavy metal is present :
• Reddish brown when hot and yellow when cold, Lead salt.
• Yellow when hot and white when cold, Zinc salt.
• Almost black when hot and vest red when cold, Iron salt.
ACTION OF HEAT
2. Check for evolution of gas(es)
• All carbonates decompose when heated to release carbon dioxide except
for potassium carbonate and sodium carbonate.
• Group II nitrates & Tr. Metal nitrates decompose when heated and release
oxygen and nitrogen dioxide.
• Group I nitrates (potassium nitrate and sodium nitrate) only release oxygen
gas.
• Some Ammonium compounds decompose to form ammonia.
ACTION OF HEAT
Carbonate
Salt
Copper (II)
Carbonate
Sodium
Carbonate
Potassium
Carbonate
Magnesium
Carbonate
Zinc
Carbonate
Lead (II)
Carbonate
Colour of
Salt before
heating
Green
Colour of residue
Hot
Cold
Effect on
Limewater
Black
Black
White
-
-
Limewater
turns milky
No change
White
-
-
No change
White
White
White
White
Yellow
White
White
Brown
Yellow
Limewater
turns milky
Limewater
turns milky
Limewater
turns milky
ACTION OF HEAT
• Nitrate salts also undergo decomposition on heating.
• Most metal nitrates decompose to produce a metal oxide, nitrogen dioxide
and oxygen.
• Sodium nitrate and potassium nitrate decompose to produce nitrite salts
and oxygen.
• Nitrogen dioxide is a brown gas. It is an acidic gas that turns moist blue
litmus paper red. Hence, dissolving it in water produces a colourless acidic
solution. The colourless oxygen gas rekindles a glowing wooden splint.
ACTION OF HEAT
Nitrate Salt
Colour
of Salt
before
heating
Colour of Residue
Tests for gases evolved
Hot
Cold
Colour of gas
Glowing
Splint
Moist Blue
Litmus paper
Copper(II) nitrate
Blue
Black
Black
Brown gas &
colourless gas
Rekindles
Turns red
Sodium nitrate
White
White
White
Colourless gas
Rekindles
No change
Potassium nitrate
White
White
White
Colourless gas
Rekindles
No change
Calcium nitrate
White
White
White
Brown gas &
colourless gas
Rekindles
No change
Magnesium nitrate
White
White
White
Brown gas &
colourless gas
Rekindles
Turns red
Zinc Nitrate
White
Yellow
White
Brown gas &
colourless gas
Rekindles
Turns red
Iron (III) Nitrate
Brown
Brown
Brown
Brown gas &
colourless gas
Rekindles
Turns red
ACTION OF HEAT
• Initial heating of ammonium chloride causes the salt to sublime.
• On further heating, decomposition takes place to produce ammonia and
hydrogen chloride (white fumes).
• When ammonium chloride is heated in a test tube, the lighter ammonia gas
will emerge first and turn a piece of moist red litmus paper blue.
ACTION OF HEAT
2. Check for evolution of gas(es)
• When a salt is heated strongly, it may decompose. One or more gases may
be liberated. Each gas can be identified by
•
•
•
•
noting its colour.
testing it with moist red litmus paper.
testing it with limewater.
testing it with glowing wooden splint.
ACTION OF HEAT
Solid X
CO32NO3-
Gas which turns limewater to white ppt
Brown gas liberated. Turns moist blue litmus
paper red. Colourless gas which relights a
glowing splint.
Colourless gas which relights a glowing splint.
Heat
What is happening to the solid?
• Effervescence/Fizzing
• Solid Melts
• Colour of the residue (hot/cold)
NH4+
MY.nH2O
Sublimation occurs, white fumes, condensation,
Gas turns moist red litmus paper blue, residue is
colourless or no residue is present.
Condensation/Moisture on the walls of the tube
TESTING FOR GASES
Gas
Ammonia
Colour & Smell
Colourless,
pungent
Carbon Dioxide
Colourless,
odourless
Hydrogen
Colourless,
odourless
Colourless,
Odourless
Pale green,
chocking smell
Oxygen
Chlorine
Test
Test Result
Hold damp red Paper turns blue
litmus paper in
gas
Bubble gas
Limewater turns
through
milky and gives
limewater
a white ppt
Hold a lighted
Burns with a
splint in gas
squeaky pop
Hold a glowing
The splint
splint in gas
relights
Hold a glowing
Paper is
splint in gas
bleached white
TESTING FOR CATIONS
• Cations can be identified by adding aqueous sodium hydroxide and
aqueous ammonia.
• Most cations (except H+, Na+, K+ and NH4+) give precipitates (insoluble salts)
with these alkalis.
• Al3+, Ba2+, Ca2+, Mg2+ & Zn2+ give a white ppt with aqueous NaOH.
• Mn2+ gives a pale brown ppt with aqueous NaOH/Ammonia.
• Fe2+, Fe3+, Cr3+, Cu2+ form a coloured ppt with aq. NaOH/Ammonia.
• Al3+, Mg2+ & Zn2+ form a white ppt with aqueous Ammonia.
TESTING FOR Al3+ ions
Add NaOH (aq)
White ppt White ppt dissolves
in excess to form a
colourless solution
Add NH3 (aq)
White ppt White ppt is insoluble
in excess aqueous
ammonia
TESTING FOR NH4+ ions
1. Add NaOH(aq)
2. Warm gently
3. Test gas given off with damp red litmus paper
TESTING FOR Ba2+ ions
Add NaOH (aq)
Faint white ppt
Add NH3 (aq)
Add H2SO4 (aq)
No observable change
White ppt formed
TESTING FOR Ca2+ ions
Add NaOH (aq)
Add NH3 (aq)
White ppt.
Insoluble in
excess
No observable change
TESTING FOR Cr3+ ions
Add NaOH (aq)
Grey green ppt
Soluble in
excess to give a
dark green
solution
Add NH3 (aq)
Grey green ppt.
Insoluble in
excess.
TESTING FOR Cu2+ ions
Add NaOH (aq)
Pale blue ppt.
Insoluble in
excess
Add NH3 (aq)
Blue ppt
Dissolves in
excess to form
a deep blue
solution
TESTING FOR Fe2+ ions
Add NaOH (aq)
Green ppt.
Insoluble in
excess
Green ppt turns
brown in
contact with air
Add NH3 (aq)
Green ppt.
Insoluble in
excess
TESTING FOR Fe3+ ions
Add NaOH (aq)
Red brown ppt.
Insoluble in
excess
Add NH3 (aq)
Red brown ppt.
Insoluble in
excess
TESTING FOR Mg2+ ions
Add NaOH (aq)
White ppt.
Insoluble in
excess
Add NH3 (aq)
White ppt.
Insoluble in
excess
TESTING FOR Zn2+ ions
Add NaOH (aq)
White ppt.
Soluble in
excess
Add NH3 (aq)
White ppt.
Soluble in
excess
TESTING FOR Mn2+ ions
Add NaOH (aq)
Off white ppt which
turns pale brown.
Insoluble in excess.
Add NH3 (aq)
Off white ppt which
turns pale brown.
Insoluble in excess.
TESTING FOR H+ ions
Add a carbonate salt
Effervescence
Insert blue litmus paper
Turns red
SUMMARY
Mg2+
Cr3+
SUMMARY
Ba2+
Mg2+
SUMMARY
SUMMARY
ADDITIONAL CONTENT
SUMMARY
SUMMARY
SUMMARY
SUMMARY
DETECTING ANIONS
Cations can be divided into three major groups as:
• Those that react with (major) dilute acids to give off gases (Carbonate, Sulphite)
• Those that react with concentrated sulphuric acid to liberate gases (Carbonate,
Nitrate)
• Those that react with neither dilute acids nor concentrated sulphuric acid
(Sulphate, Nitrite, Halides).
Test for Carbonate ions
Add dilute acid
Bubble the gas through
limewater
Effervescence.
Bubbles of colourless,
odourless gas.
Limewater forms
a white ppt
Test for Carbonate ions
CO32-(aq) + 2H+(aq) → CO2(g) + H2O(l)
CO2(g) + Ca(OH)2(aq) → CaCO3(s) + H2O(l)
Test for Carbonate ions
Squeeze as much air
as possible out of the
dropper & keep it
squeezed.
Position the tip of
the dropper a few
cm above the liquid
Add acid & release
bulb of the dropper to
suck some of the gas
Test for Carbonate ions
Put the dropper tip
into the limewater
and squeeze the bulb
to expel the gas
Suck limewater into
the dropper and
expel it out again
Test for Hydroxide ions
Add a few drops of
Silver nitrate solution
Mud-brown ppt is formed
Test for Hydroxide ions
Add a metal salt e.g CuSO4
A white/coloured ppt is formed
Test for Hydroxide ions
Add an Ammonium salt + heat gently
Moist red litmus paper turns blue
Test for Chloride ions
Add a few drops of A white ppt is formed if chloride is present
Silver nitrate solution
Test for Chloride ions
Add aqueous
ammonia solution
A white ppt is
formed if chloride
is present
The ppt dissolves
to form a
colourless solution
Test for Iodide ions
Add a few drops of
Silver nitrate solution
A pale yellow ppt is formed if iodide is
present
Test for Iodide ions
Add aqueous
ammonia solution
A pale yellow ppt
is formed if iodide
is present
The ppt does not
dissolve in excess
Test for Bromide ions
Add a few drops of
Silver nitrate solution
A cream ppt is
formed if bromide
is present
The ppt does not
dissolve in excess
Test for Bromide ions
Add aqueous
ammonia solution
A cream ppt is
formed if bromide
is present
The ppt does not
dissolve in excess
if dilute but
dissolves if
concentrated.
Test for Nitrate ions (Devarda’s Test)
Add aqueous sodium
hydroxide & warm
gently
Add Aluminium
foil/powder
(Effervescence)
Turns moist red
litmus paper blue
Test for Nitrite ions
Add aqueous sodium
hydroxide & warm
gently
Add Aluminium
foil/powder
(Effervescence)
Turns moist red
litmus paper blue
Test for Nitrite ions
Add an acid to
KMnO4
Add analyte to acidified
aqueous KMnO4
(Purple colour decolourises)
Test for Sulphate ions
Add BaCl2 (aq) or
Ba(NO3)2 (aq)
White ppt
Add dilute strong acid
(White ppt, insoluble
in excess acid)
Test for Sulphite ions
Add BaCl2 (aq) or
Ba(NO3)2 (aq)
White ppt
Add dilute strong acid
(Soluble in excess
acid)
Test for Sulphite ions
Add an acid to
KMnO4
Add analyte to acidified
aqueous KMnO4
(Purple colour decolourises)
Test for Thiosulfate ions
Add an acid to
analyte
Pale yellow ppt