Titration

1. KEYPOINTS IN TITRATION

2.

Learning Objective
- Be able to carry out titrations and
the associated calculations
Success Criteria
- Carry out an acid-base titration
- Perform calculations associated
with titration
Keywords
titration…..titrant…..titrand / analyte…..
end-point…..equivalence point…..indicator…..
parallax error

3. Task: Label the parts of a titration set-up.

4. Titration

Titration is a quantitative technique that is used to
accurately determine the concentration of a substance in
solution.
pipette bulb
burette
(buret)
pipette
(volumetric
pipette)
ring stand
volumetric flask
funnel
conical
(Erlenmeyer)
flask
beaker
The purpose of a titration is to determine
the volume of solution required to reach an endpoint. An endpoint is an
observable physical change, such as a colour change.

5. Making Measurements

• Always read at eye level to
avoid errors due to parallax
• For colourless solutions, take readings at the lower
meniscus

6.

During a titration, a solution of known
concentration, called a standard solution
(titrant), is added to a solution of unknown
concentration.
In analytical chemistry, a standard
solution is a solution containing a precisely
known concentration of an element or a
substance.
A solution of known concentration (titrant)
is used to determine the concentration of an
unknown solution (titrand or analyte).
Acid-Base
Titration

7.

How are the results of a titration used to calculate the
concentration of an unknown acid solution?
Average volume of NaOH = 20.00 + 19.90 + 20.10 = 20.00 cm3
3

8.

Common mistakes in table of results
Non-uniform decimal
places
Headings
do not include units
Unrealistic
measurement,
the second decimal
place can only be
.00 or .05
Measurement with a range
of more than 0.2 should
NOT be used in averaging

9. Recording Measurements

• Ensure to use uniform decimal places in your readings. This confirms
that your are working at similar precision levels
1
✓ uniform 2 decimal places
in all measurements
✓1 Headings include units
✓1 Realistic measurement ,
the second decimal place can
only be .00 or .05
✓1 Measurement with a
range of more than 0.2 not
be used in averaging
* No. or #
** V of FB 1 in cm3 or / cm3 or (cm3)
*** t in seconds or /s or (s)
time and temperature → ONE decimal places
volume
→ TWO
decimal places
mass
→ THREE decimal places

10. Procedures: Titration of hydrochloric acid with NaOH

11.

12.

Recording Measurements
In the space below record your burette readings for this rough titration.
The rough titre is ……………….. cm3.
[1]
1 mark for 2 decimal places

13. Recording Measurements

Record in a suitable form below all of your burette readings and the volume of FA 2 added in each accurate
titration.
Make sure that your recorded results show the precision of your practical work.
Titration numbers
Initial burette reading /cm3
1
0.00
2
3
4
✓ uniform 2 decimal places in all
measurements
Final burette reading /cm3
✓ Headings include units
Volume of NaOH used for titration
(Titre) /cm3
Experiment number
Initial volume of FА2/
cm3
Final volume of FА2/
cm3
Volume of FА2 used
for titration/ cm3
Exp 1
Exp 2
Exp 3
✓ Realistic measurement , the
second decimal place can only be
.00 or .05
✓ Measurement with a range of
more than 0.2 not be used in
averaging
[7]

14. Recording Measurements

Record in a suitable form below all of your burette readings and the volume of FA 2 added in each accurate
titration.
Make sure that your recorded results show the precision of your practical work.
Experiment number
Initial volume of FА2/
cm3
Final volume of FА2/
cm3
Volume of FА2 used
for titration/ cm3
Exp 1
Exp 2
Exp 3
• 1 mark for draw and table and
value with units
• 1 mark for 2 decimal places last 0
or 5
Accuracy teacher and student
• scaled titre within ±0.2 of supervisor’s titre (5)
• scaled titre within ±0.3 of supervisor’s titre (4)
• scaled titre within ±0.4 of supervisor’s titre (3)
• scaled titre within ±0.5 of supervisor’s titre (2)
• scaled titre within ±0.6 of supervisor’s titre (1)
[7]

15.

Recording Measurements
(b) (i) Calculate the average volume of NaOH.
[1]
correct mean calculated to either 2 or 3 decimal places using
results that are within ±0.20
✓ Measurement with a range of
more than 0.2 not be used in
averaging

16.

Recording Measurements
(ii) From your accurate titration results, obtain a suitable value to be used in your
calculations. Show clearly how you have obtained this value.
25.0 cm3 of FA 1 required ........................ cm3 of FA 2
[1]
2 decimal places

17.

Recording Measurements
(с) Сalculations
(i) Calculate how many moles of NaOH were present in the volume of FA2
………………. mol of NaOH
[1]
Write a balanced equation for the reaction:
HCl + NaOH → NaCl + H2O
1
:
1
Calculate the number of moles of alkali (known):
moles = concentration (mol/dm-3) × volume (dm3)
= 0.10 × (11.00 / 1000)
= 0.0011 moles NaOH
n(NaOH)=CV/1000
present standard data
1 mark

18.

Recording Measurements
(ii) Calculate how many moles of HСl were present in 25.0 cm3 of FA 1.
........................ mol of HСl
[1]
n(NaOH) = n(HCl)

19.

Recording Measurements
(ii) Calculate how many moles of HСl were present in 25.0 cm3 of FA 1.
The concentration of HСl in FA 1 was ................................. mol·dm–3
[1]
C(HCl) = n/V 1 mark
1 mark – data
1 mark – 3 or 4 decimal places and unit
Calculate the concentration of the HCl (unknown) solution in
mol/dm3:
moles
= 0.0011 / (0.025)
concentration =
volume (dm3)
= 0.044 mol/dm3

20. Sample titration calculations

If 20 cm3 of 0.1 molar NaOH neutralizes 25 cm3 of HCl of unknown
concentration.
Working:
1. Write a balanced equation for the reaction:
HCl + NaOH → NaCl + H2O
1
:
1
2. Calculate the number of moles of alkali (known):
moles = concentration (mol/dm-3) × volume (dm3)
= 0.1 × (20.00 / 1000)
= 0.002 moles NaOH
3. Calculate the concentration of the HCl (unknown) solution in
mol/dm3:
moles
= 0.002 / (0.025)
concentration =
volume (dm3)
= 0.08 mol/dm3

21. Another titration calculations…

Apparatus and chemicals:
FA 1 is sulfuric acid, H2SО4, of approximate
concentration 0.7 mol·dm-3 .
FA 2 is 0.150 mol·dm-3 sodium hydroxide
(a) Method Dilution Pipette 25.0 cm3 of FA 1
into the 250 cm3 graduated (volumetric)
flask labelled FA 3. Make the solution up
to the mark using distilled water (you can
use measuring cylinder of bottle with
distilled water). Shake the flask to mix the
solution of FA 3.
(b) Titration with phenolphthalein Rinse out
the pipette with distilled water and then
with FA 3. Pipette 25.0 cm3 of FA 3 into a
conical (Erlenmeyer) flask. Add 5 drops of
phenolphthalein indicator to the flask.
The indicator should remain colourless.
(c) Fill the burette with FA 2. Titrate FA 3
with FA 2, until a permanent pale pink
colour is obtained. You should perform a
rough titration. In the space below record
your burette readings for this rough
titration
23.85cm3 average value ignoring
with range greater than 0.20
23.85 X 0.150 = 0.00358 moles
1000
1
:
2
(½ x 0.00358) 0.00358 moles
0.00179
250 X 0.00179 = 0.0179
25

22.

Apparatus and chemicals:
FA 1 is sulfuric acid, H2SО4, of approximate
concentration 0.7 mol·dm-3 .
FA 2 is 0.150 mol·dm-3 sodium hydroxide
(a) Method Dilution Pipette 25.0 cm3 of FA 1
into the 250 cm3 graduated (volumetric)
flask labelled FA 3. Make the solution up
to the mark using distilled water (you can
use measuring cylinder of bottle with
distilled water). Shake the flask to mix the
solution of FA 3.
(b) Titration with phenolphthalein Rinse out
the pipette with distilled water and then
with FA 3. Pipette 25.0 cm3 of FA 3 into a
conical (Erlenmeyer) flask. Add 5 drops of
phenolphthalein indicator to the flask.
The indicator should remain colourless.
(c) Fill the burette with FA 2. Titrate FA 3
with FA 2, until a permanent pale pink
colour is obtained. You should perform a
rough titration. In the space below record
your burette readings for this rough
titration
250 X 0.00179 = 0.0179
25
Concentration = Moles
Volume
= 0.0179
0.025
= 0.716 mol dm-3
You can see that our answer is quite close to the
approximate concentration given

23. Reflection

• What has been learned
• What remained unclear
• What is necessary to work on