Practical Experiment for Acid-Base Titration

This document is a practical experiment for Acid-Base Titration. It compares the analysis of household ammonia using the indicator method and pH metry instrumental technique. The document includes the aim, hypothesis, apparatus and chemicals used, risk assessment, variables and constants, procedure, observation table, balanced equation, calculation steps, graph, and a comparison of the two techniques. It also provides references for further reading.

a typed sheet of one High
School experiment on
AcidBase Titration to
compare the analysis of
household ammonia using
Indicator method and
pH metry in Indicator
method and pH metry in

TABLE OF CONTENTS
Title..................................................................................................................................................3
Aim..................................................................................................................................................3
Hypothesis.......................................................................................................................................3
Apparatus and Chemical..................................................................................................................3
Risk Assessment..............................................................................................................................3
Variables, Constants and control.....................................................................................................3
Diagram...........................................................................................................................................4
Procedure.........................................................................................................................................5
Observation Table............................................................................................................................6
Balanced Equation...........................................................................................................................7
Calculation steps..............................................................................................................................7
Graph...............................................................................................................................................9
Comparison of two techniques........................................................................................................9
REFERENCES..............................................................................................................................11

Title
Practical Experiment for Acid-Base Titration.
Aim
To make a comparison regarding the analysis of household ammonia using the indicator method
and pH metry instrumental technique.
Hypothesis
The hypothesis used in this experiment is that the pH of a solution may be easily or
accurately determined by the electrochemical measurements by making use of device known as
pH meter with a pH sensitive electrode and a reference electrode. The electrode potential for the
proton can be elaborated as:
Where E is considered to be measured potential, E0 is the standard electrode potential at aH+ =
1mol/L, T is the temperature in Kelvin, F is the Faraday constant and R is the gas constant.
Apparatus and Chemical
50 ml burette, 2*50 ml beakers, 3-4 * 100 mL Conical flasks, funnel, 20 mL Pipette, Methyl
orange indicator, 250 mL volumetric flask, anhydrous sodium carbonate (Na2CO3) powder
(Pattarapongdilok and et.al., 2019).
Risk Assessment
There can be risks when the safety glasses and laboratory coat are not wore by the individual
for the experiment. Also, there are major risks from ammonia vapour which causes irritation in
the eyes, skin and respiratory system (Nogueira and et.al., 2017). The household ammonia must
be dispensed from the stock bottle in a well ventilated area or the cupboard of fume.
Variables, Constants and control
The concentration of HCl is variable as this cannot be determined and this is why this can
be used as a standard against the cloudy ammonia. The titrate volume is constant which is 20-30
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mL of a 50 mL burette. The mass of Na2CO3 is constant which 1.06 g is and the volume of
volumetric flask is 250mL (Desriana and et.al., 2020). The molecular weight of HCl is fixed
which is 36.5g/mol. The control must be taken regarding the volume of the substances and also
the changes in the variables must be monitored accordingly. It must also be controlled that the
titration is done with pH electrode and helps in determining the equivalence point. The amount
of analyte must be calculated from the result of titration.
Diagram
Figure 1: Titration Setup
Source: Belford, 2021
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Figure 2: Experimental setup of acid-base titration
Source: Acid-Base titration, 2021
Procedure
Step 1: Preparation of Na2CO3 standard solution (stock)
An exact mass of 1.06 gm is weighed of anhydrous Na2CO3 and this is diluted to 250 mL in
volumetric flask. This is then mixed by inverting many times. This standard solution
concentration is then calculated so that this can be used in the titration against the solution of
HCl.
Step 2: Standardisation of HCL solution
The burette is cleaned and then filled with HCl solution. The pipette is cleaned with water
and Na2CO3 and then 20.0 mL aliquot of Na2CO3 is transferred through the pipette and then 3-4
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drops of Methyl Orange indicator is added to it. This is done many times while titrating. The
aliquots are titrated with HCl solution from the burette and also it is ensured that the contents in
the flask are homogenous. The solution must be turned to salmon pink gradually. This is done by
adding the HCl drop by drop (Liu and et.al., 2018). Then the volume of HCl which was
responsible for that pink colour is noted. Three readings are taken and then the HCl solution
concentration is calculated.
Step 3: Analysis of Cloudy Ammonia
The dilution of cloudy ammonia solution is prepared by using 20mL pipette. 20 mL
aliquots of diluted cloudy ammonia are then transferred to each of 100 mL conical flasks along
with 3-4 drops of methyl orange indicator. The titration process is then repeated 3-4 times.
Observation Table
Table 1: Na CO standard solution₂ ₃
Mass of
Na CO (g)₂ ₃
Volume
(mL)
Concentration of
Na CO (mol/L)₂ ₃
1.06 250 0.0400 ± 0.592%
Table 2: Titration of Na CO vs HCl solution₂ ₃
Trial Volume of 0.04M
Na CO (mL)₂ ₃
Volume of HCl
(mL)
1 20 15.2
2 20 15.5
3 20 15.5
Table 3: Titration of HCl vs NH solution₃
Trial Volume of diluted NH₃
(mL)
Volume of HCl
(mL)
1 20 18.8
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2 20 18.6
3 20 18.7
Balanced Equation
Na CO (aq) +₂ ₃ 2HCl → 2NaCl (aq) + CO (g) + H O (l)₂ ₂
Stage 1: First equivalence point
Na CO₂ ₃ (aq) + HCl (aq) → NaHCO₃ (aq) + NaCl (aq)
Stage 2: Second equivalence point
NaHCO₃ (aq) + HCl (aq) →H O₂ (l) + NaCl (aq) + CO₂ (g)
Calculation steps
To determine the concentration of the ammonia, the number of moles of NH are required which₃
can be determined through the use of the mole ratio of the balanced equation:
NH (aq) + HCl (aq) → NH (aq) + Cl (aq)₃ ₄⁺ ⁻
Therefore the ratio is 1:1; for every molecule of NH there is one molecule of HCl.₃
n (NH ) = n (HCl)₃
= 1.94 x 10 ³ mol⁻
∴ c (NH ) = n / V₃
= 1.94 x 10 ³ mol / 0.020L⁻
= 0.097M
To account for the dilution of 20mL sample cloudy ammonia up to 250mL, the original
concentration is determined via:
c V = c V₁ ₁ ₂ ₂ where 1 = initial, and 2 = final
∴c =₁ c V / V₂ ₂ ₁
7

c (NH ) = 0.097M₁ ₃ x 0.250L / 0.020L
= 1.21M
To compare with the 20g/L claim, the molarity is converted to grams per litre:
n (NH ) = cV₃
= 1.21M x 1 L
= 1.21 mol
M (NH ) = 17g/mol₃
∴ m (NH ) = nM₃
= 1.21 mol x 17g/mol
= 20.6g
= 20.6g
Percent Difference
% Difference = [experimental - theoretical] / [theoretical] x 100%
^^ note absolute difference brackets above
% Difference = (20.6g/L - 20g/L) / (20g/L) x 100%
= 3%
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Graph
Figure 3: HCl vs Na2Co3 pH curve
Source: Boman, 2018
Figure 4: Hydrochloric acid vs ammonia pH curve:
Source: Boman, 2018
Comparison of two techniques
Table 4: Comparison of ammonia content
Claimed NH content (g/L)₃ Experimental NH content (g/L)₃
20 20.6 ±0.536
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This minor difference provides evidence regarding the authenticity of the claim and also some
indication of tolerances of the manufacturing of products.
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REFERENCES
Books and Journals
Desriana, D. and et.al., 2020, February. The effectiveness of an interactive module in improving
students’ conceptual understanding of acid-base titration. In Journal of Physics:
Conference Series (Vol. 1460, No. 1, p. 012092). IOP Publishing.
Liu, Y. and et.al., 2018. Acid-base properties of kaolinite, montmorillonite and illite at marine
ionic strength. Chemical Geology. 483. pp.191-200.
Nogueira, S.A. and et.al., 2017. Monitoring acid–base titrations on wax printed paper
microzones using a smartphone. Micromachines. 8(5). p.139.
Pattarapongdilok, N. and et.al., 2019. Natural Indicator for Acid-Base Titration from Thai
Yellow Flower Extracts. International Journal of Chemical Engineering and
Applications. 10(1).
Online
Acid-Base titration, 2021. [ONLINE]. Available through :<
https://www.the-mad-scientist.net/g12-ib-sl-chemistry-madlab/august-14-18-2017>
Belford, R., 2021. Acid-Base Titrations. [ONLINE]. Available through :<
https://chem.libretexts.org/Courses/University_of_Arkansas_Little_Rock/
Chem_1403%3A_General_Chemistry_2/Text/17%3A_Aqueous_Equilibria/
17.03%3A_Acid-Base_Titrations>
Boman, S., 2018. Titrations. [ONLINE]. Available through :<
http://www.anglesandacid.com/titrations.html#.YLXa8qgzbIU>
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