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Titration of Hydrochloric Acid with Sodium
Hydroxide
(Mostafa ElSanousi, 10/09/22, Chemistry HL)
I. Introduction & Purpose
Research Question
What is the method to determine the concentration of NAOH through a titration
experiment when NAOH is diluted into H2O and C20H14O4 (phenolphthalein or
HPh) is mixed in.
Introduction
Titration experiments may seem niche and impractical to observe and utilize in
real-world scenarios but that is simply not the case. I, for one, understood the
importance of titration experiments in the automotive industry in order to produce the
most efficient biodiesel fuel. In this case, pH level is determined to find how much of
a base is needed for balance and achieving the correct pH level in the fuel.
Therefore, titration experiments undoubtedly were brought to my attention as a
possible IA topic.
II. Background & Design
Background
Important Terms:
Titration – Method of determining the concentration of a dissolved substance (in this
case it is 0.1M of NAOH with a volume of 250cm^2) in terms of the smallest amount of
a reagent required to bring about the end point of the reaction (e.g. color change).
Titrant – A substance (the regent) that is used to bring about the end point of the
reaction between it and the analyte + HPh.
Indicator (C20H14O4) – C20H14O4, or phenolphthalein, is a colorless, weak acid,
that is used in titrations in order to identify the end point of titration.
Analyte – The analyte in a titration experiment is the unknown concentration (in this
case it is the NAOH diluted into H2O).
End Point – The point in a titration experiment when the indicator shows that the
amount of reactant necessary for a complete reaction has been added.
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Neutralization Reaction – Neutralization reactions are a type of reaction where an acid
and a base react and result in an ionic compound or water sometimes. When the
reaction is in water, the neutralization reaction depends on there being no excess of
hydrogen or hydrogen ions in the solution.
Important Concepts:
Molarity: M = n/v where n is moles of solute and v is liters of solution.
Molarity was used as this was the given concentration of NAOH in the beginning of
the experiment that we used to find the amount of moles present in 0.1M
concentration of NAOH if it has a volume of 250 cm^3.
Dm^3 = Cm^3/1000
This is important as dm^3 is the standard unit used in titration experiments and using
cm^3 would result in errors.
C = n/v – > n = c*v
According to the initial formula to determine concentration, moles are equal to the
concentration multiplied by the volume. This formula is important as it allows us to
determine the amount of moles in NAOH that has a concentration of 0.1M and has a
volume of 250 cm^3 which is rewritten to 0.250 dm^3 as it has to be in terms of dm^3
in order for the formula to function.
The connection to pH and the pH indicator:
pH measures the acidity or basicity of an aqueous solution. In this case, the pH level
changes according to the base in the titration experiment which is NAOH and since it
is a base the pH indicator will have a pink hue as it is initially colorless in pH levels
less than 8.5 but has a color in pH levels higher than 8.5.
Calculating amount of moles using molarity:
Molarity x volume = number of moles
In this case, at the equivalence point –
(MNaOH)(VNaOH) = (MHCl)(VHCl)
Titration experiments are important to chemistry as they allow for an accurate
determination of solution concentrations of the analyte. As discussed before, they also
hold implications in real-life situations, and are, therefore, valuable to various
industries (such as the automotive industry). Titration experiments are experiments
where a volume of a solution of a known concentration is added to a volume of
another solution in order to determine its concentration.
Hypothesis
I hypothesize that the concentration of NAOH + H2O will be less than the initial
concentration of NAOH as dilution results in the decrease in concentration.
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Furthermore, I believe that since the HPh will be dropped into the NAOH, the
solution will become a pink color compared to if it was being dropped into HCl
where it would retain its clear, transparent appearance. The reason for this is
that HPh is colorless in solutions with a pH level lower than 8.5 and has a pink
hue in pH levels above 9.0. Therefore, since the HPh is being dropped into a
base (NAOH), although being diluted into H20, its pH level is approximately 9.0
and thus the solution will develop a pinkish hue and only lose it when it becomes
transparent and has a pH level less than or equal to 8.5 which would mean that
the end point has been reached (concentration of hydrogen and hydrogen ions in
the solution are balanced and thus the color goes from pink to transparent again)
and the concentration of the NAOH + H2O has been quantified.
Design
- Independent Variable: Volume of base (250cm^2/0.250dm^3 of NAOH)
- Dependent Variable: The molarity of NAOH as identified through the final
burette reading.
- Controlled variables:
Variable
controlled
Why it’s important to control
Volume of
Distilled
Water Into the
NaOH
The volume of distilled water
into the NaOH will affect the
final concentration due to
the amount of dilution that
the NaOH will go through
which will decide how much
the initial concentration
decreases due to dilution.
Surface Area of
Volumetric Flask
The surface area of the
volumetric flask that we used to
dilute the NaOH with water
accurately is important as it
allowed for a specific
concentration of diluted NaOH
(50mL) that would become
different if we used a different
How this experiment
will control or monitor
the
variable
This will be monitored
throughout the
experiment through the
use of a volumetric
flask that is marked
with a line that allows
us to use the same
amount of distilled
water to dilute the
NaOH each and every
time.
The surface area of the
volumetric flask will be kept
constant as we will be using
the same exact flask.
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volumetric flask with different
proportions.
Mass of NAOH
diluted into H2O
(1g)
The mass of NaOH that we
solved for (1g) using the given
concentration (0.1M) and volume
(250cm^3) needs to be kept
constant as if it is different every
time there will be a different
concentration of diluted NaOH in
the final burette reading.
The concentration, and thus,
the mass, of the NaOH was
kept constant throughout the
entirety of the experiment as
we have had it measured
out in the beginning using
the mass scale to be 1
gram.
Addition of HPh
indicator (2 drops)
It is important to keep the
amount of HPh indicator used
constant as having a different
one every time will affect the pH
as it is still an acid despite being
a weak one.
The same dropper used to
add the HPh indicator into
the solution will be reused to
enforce similar results in the
final burette reading.
Room
temperature (must
remain constant)
If the solution is at a higher or
lower temperature because of
the general room temperature
then the volumetric flask
readings may be incorrect as it
will contract or expand meaning
that the final burette reading will
be wrong.
The room temperature will
be kept constant as the
temperature system will not
be tampered with or touched
so as to keep the
temperature constant.
III. Procedure & Safety
Materials
Burette (1)
250mL Erlenmeyer Flask (3)
1 L of Distilled Water (1)
pH Indicator (phenolphthalein) (1)
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Dropper (1)
Retort Stand and Clamp (1)
100mL Volumetric Flask (1)
Wash Bottle (1)
50mL Beaker (1)
Gloves
Lab Coat
Procedure
1. Wear safety equipment (e.g. gloves and lab coat).
2. Calculate amount of NaOH in grams that will be used in the titration
experiment given volume (250cm^3) and molarity (0.1M).
3. Using a mass scale, weigh exactly 1 gram of NaOH that will be used in the
experiment.
4. Remove the covering from the volumetric flask and fill approximately ¼ of
the flask.
5. Add 1g of NaOH that you measured just before and begin to carefully move
the volumetric flask in a circular motion to dilute the sodium hydroxide.
6. Proceed to fill the volumetric flask to the 50mL mark once the dilution of
sodium hydroxide is complete.
7. Add the diluted substance equally to three erlenmeyer flasks at the
indicated mark (25mL) provided in order to keep the amount constant.
8. Carefully add two drops of C20H14O4 (HPh) into each of the three
erlenmeyer flasks.
9. Add HCl into the burette until it reaches the 0.00 mark in order to avoid
mistakes in the final reading.
10. To begin the titration, place one of the three erlenmeyer flasks under the
burette mechanism so as the tip of the burette is within the flask to avoid
drippage outside the flask.
11. For the first trial, carefully calibrate the flask by turning the tap so as precise
and orderly droplets are going into the flask.
12. Turn off the tap when the diluted NaOH (which turns pink due to the HPh)
becomes a colorless liquid as that means it has reached the end point and
the titration has been successful.
13. Check the amount of HCl that is left over and that is the experimental
concentration of diluted NaOH.
14. Record your data.
15. Repeat the process two more times and record the data as well.
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Diagram
Safety/Ethical/Environmental Issues
NaOH Dangers: Contact with NaOH may result in serious burns to the eyes, skin, and
digestive system or lungs that can lead to serious injuries, or even death.
HCl Dangers: HCl is extremely hazardous when it comes into contact with the skin or
eyes or when it is inhaled or ingested and can cause permanent damage to your
organs.
HPh Dangers: HPh may cause eye irritation and skin irritation upon contact with skin
and may be harmful if it is absorbed through the skin as well.
Considerations: It is important to wash your hands with a large volume of water if you
come into contact with any of the mentioned substances during the replication of this
titration experiment.
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IV. Data Processing
Data Tables (give them meaningful titles)
DATA COLLECTION (RAW)
Amount of Distilled
Water (mL)
Volume of HCl (mL)
Trials
Initial Burette
Reading
Final Burette
Reading
50
1st Trial
0.00
44.5
50
2nd Trial
0.00
44.2
50
3rd Trial
0.00
44.3
Calculations
Average of the three trials:
44.5 + 44.5 + 44.3 divided by 3 = 44.33mL of HCl
Concentration of NaOH:
At the equivalence point – (MNaOH)(VNaOH)=(MHCl)(VHCl)
Average volume of HCl used = 44.33mL - 0.00 of HCl = 44.33mL of HCl
(MNaOH) = (MHCl)(VHCl)/(VNaOH)
(MNaOH) = (0.1)(44.33mL)/25mL
(MNaOH) = 0.17732 M
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Graphs:
Example of Strong Base-Strong Acid Graph and its general logarithmic trend at the
equivalence point:
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V. Conclusion
Consequently, based on my titration experiment results seen in the above graph and
how they do not represent a properly logarithmic function, it is safe to say that there
may have been some issues in the reporting or conduction aspect of the experiment.
Based on the data I worked out, the final concentration of NaOH that the titration
experiment was meant for, turned out to be 0.177M while the initial concentration was
0.1M. Therefore, this cannot be true as the dilution that the NaOH went through
(NaOH(aq) + HCl(aq) → NaCl(aq)+H2O(I); 1:1 molar ratio) means that the
concentration should be less than 0.1M as concentration decreases when becoming
diluted. The experiment could have gone better if some more measures were taken for
greater precision and accuracy, as well as some considerations into the actual
measurements and measuring devices being used as they have tampered with the
final results eventually at the end as well. Furthermore, titration experiments are
faulted in their nature as their main limitation is that the end point of the titration does
not necessarily equal the equivalence point. All in all, it was an informative experience
that facilitated the conceptual understanding of a titration, its property and construct,
and its product.
VI. Analysis
Sources of Error and Improvements
Source of Error
Mass Scale
How it could skew
(increase or decrease
the final result)
Suggested Procedural
Improvement
The mass scale could
result in an excess or
lack of NaOH needed for
the titration to be
accurate, therefore, it
could skew the final
results so that it
increases as the
concentration of NaOH in
the water would be
higher.
In order to ensure that the
mass scale does not
malfunction or to check that
it is giving precise or
accurate measurements, it
may be better to have two
available to have a few
attempts instead of using
one and taking it for what it
is worth.
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HPh dropper
The HPh dropper was not
entirely precise and
sometimes leaked for
more than two drops.
This will skew the final
results as the volume of
HCl needed in mL would
be higher in order to
perform the neutralization
reaction and complete
the titration successfully;
therefore, the final
concentration of NaOH
would also be higher as
well as it would take more
to balance the pH level.
In order to procedurally
improve this aspect of the
experiment, it is best to
ensure that the dropper is
working using it and
comparing it to other
droppers to see if they are
secreting the same amount
of liquid to avoid having a
malfunctioning dropper that
may be leaking more than it
is supposed to.
Reaction Time
Reaction time is an
important factor in a
titration experiment as in
order for the exact
volume of the titrant
needed to perform a
neutralization reaction,
you must have a faster
reaction time so as the
result is as accurate as
physically possible for a
human. If it is
overestimated due to a
poor reaction time, then
the volume of HCl will be
higher, and thus the
volume of NaOH will also
be higher as well.
In order to improve upon this
procedural issue, it is
possible to perform more
than 3 trials as that will
minimize the presence of the
systematic errors that are
present due to a person’s
natural reaction time while
also giving a clear insight
into what the actual results
may be.
Unequal distribution of
substance (NAOH +
If there is an unequal
distribution of substance
This procedural issue could
be fixed through ensuring
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H2O) in conical flasks
in the conical flasks,
there will be less or more
of the volume of diluted
NaOH, and thus this
could lead to the final
concentration either
skewing upwards or
downwards based upon if
there is more NaOH in
the flask or less.
that there is an equal
distribution in the conical
flasks through precisely
measuring the amount of
substance in the flasks and
equating them to the other
flasks instead of basing it off
of your eyes which can have
issues for a number of
reasons (e.g. parallax error).