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IB Chemistry HL - Internal Assessment (IA)
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Final Internal Assessment that received a 7. Written by a IB student who graduated with a 45/45.
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IntroductionWhile studying high-level content for chapter 17 (equilibrium) and chapter 18 (acid and base), I began
to question how these two topics can be linked in a real life situation. I then realized acid and base
titration is a common industrial process, yet the conditions of the experiment may not be in a
controlled environment; the titration process may be used under varying conditions, such as different
temperature, pressure, and so forth. From the IB curriculum I am aware these factors would affect any
equilibrium present, but I became curious: to what extent? To what extent would temperature affect
the titration process involving acid and base? Why? Addressing these questions subsequently became
the central purpose for this laboratory experiment.
Aim
To see how different temperature (20.0°C, 35.0°C, 50.0°C, 65.0°C, 80.0°C) affect the volume (± 0.05
cm3) of 0.500 mol dm-3 ethanoic acid required to successfully neutralize 20.00 cm3 (± 0.05 cm3) of
1.000 mol dm-3 sodium hydroxide in a titration process using a pH metre and phenolphthalein.
Research question
What is the stoichiometric significance of temperature on neutralization, investigated by a laboratory
titration process that measures the volume (± 0.05 cm3) of 1.000 mol dm-3 ethanoic acid required to
successfully neutralize 20.00 cm3 (± 0.05 cm3) of 1.000 mol dm-3 sodium hydroxide using a pH metre
and phenolphthalein, in variable surrounding temperature (20.0°C, 35.0°C, 50.0°C, 65.0°C, 80.0°C)?
Background information and hypothesis
Titration is the addition of one solution of a known concentration of acid to an unknown concentration
of basic solution until the reaction reaches neutralization, indicated by a colour change1. Usually, the
purpose of a titration is to determine the concentration of the unknown concentration until
neutralization occurs, but in this experiment, known concentration of both the titre and the basic
solution is used to determine the effect of temperature in the titration process.
Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water2, of a mildly basic
pH at standard temperature at the equivalence point. This experiment focuses on how the temperature
would affect the neutralization between these two products. I have hypothesized two reactions:
a) When high temperature results in lower volume of acid required for neutralization
According to the Le Chatelier’s Principle3, a higher temperature alters the ionic product constant of
water (Kw); the forward reaction of 2H2O ⇌ H3O+ + OH- is favoured at a higher temperature as this
process is endothermic. For example, at a temperature of 20°C the neutral pH is 7.08 while in a
temperature of 100°C, the neutral pH is 6.14. This means that, though neutral, a higher temperature
will result in a higher pH of the solution. As an increase in temperature result in an increased pH of a
solution, we can hypothesize that as the temperature increases, less ethanoic acid will be required to
reach the transition point of the pH indicator.
a) When high temperature results in higher volume of acid required for neutralization
However, unlike water, ethanoic acid is exothermic. A high temperature will favour the backwards
reaction in the dissociation of weak acid of CH3COOH + H2O ⇌ CH3COO- + H3O+ according to the
Le Chatelier’s Principle, and subsequently alter the acid dissociation constant to decrease as
temperature increases. Therefore, according to the Van’t Hoff’s equation, we can hypothesize that a
higher temperature would require more ethanoic acid to reach the transition point of the pH indicator.
1
Titration Part 1: Scientific Introduction [However, unlike water, ethanoic acid is exothermic. A high temperature will favour the backwards reaction in the
dissociation of weak acid of CH3COOH + H2O ⇌ CH3COO- + H3O+ according to the Le Chatelier’s Principle, and subsequently alter the acid dissociation
constant to decrease as temperature increases. Therefore, according to the Van’t Hoff’s equation, we can hypothesize that a higher temperature would require
more ethanoic acid to reach the transition point of the pH indicator.
online] Available from: https://www.math.duke.edu/education/ccp/materials/calculus_projects/TitrationProj/Titration1.html [Accessed 3th July, 2015]
2
Titration of Hydrochloric Acid with Sodium Hydroxide [online] Austin Peay State University Department of Chemistry. Available from:
https://www.apsu.edu/sites/apsu.edu/files/chemistry/SP12_1011_Titration_of_Hydrochloric_Acid_with_Sodium_Hydroxide_0.pdf [Accessed 3th July, 2015]
3
Clark, J. Temperature Dependent of the pH of pure Water [online] UC Davis. Available from:
http://chemwiki.ucdavis.edu/Physical_Chemistry/Acids_and_Bases/Aqueous_Solutions/The_pH_Scale/Temperature_Dependent_of_the_pH_of_pure_Water
[Accessed 3th July, 2015]
1
, Variables
Type of Variable Variable and Range How it will be changed
Independent Variables Temperature The different temperature will be controlled by
(20.0°C, 35.0°C, using an electronic water bath, which will set
50.0°C, 65.0°C, the temperature of the surroundings and the
80.0°C) solution constant and lessen the fluctuation.
Type of Variable Variable and Range How it will be measured
Dependent Variables Volume of 0.500 mol The ethanoic acid, with the concentration
dm-3 ethanoic acid accurately sourced from an authorized source,
required for the will be accurately measured through a burette
neutralization process (cm3, ± 0.05 cm3) to measure the impact of
to occur (cm3, ± 0.05 temperature on volume required.
cm3)
Type of Variable Variable and Range How it will be controlled
Controlled Variables Concentration of 20.00g of anhydrous sodium hydroxide powder
sodium hydroxide will be measured by an electronic balance (±
0.00g) and dissolved in 500.0 cm3 (cm3, ± 0.05
cm3) distilled water to create 1.000 mol dm-3
sodium hydroxide. This solution will be
constantly used throughout the trials to
maximize precision. This has to be controlled
to minimize unwanted fluctuation in the
resulting data.
Volume of sodium 25.00 cm3 of 0.100 mol dm-3 sodium hydroxide
hydroxide solution will be measured through a pipette (±0.05cm3)
for every experiment. This has to be controlled
to minimize unwanted fluctuation in the
resulting data.
Concentration of Due to the practical difficulty involved in
ethanoic acid ensuring accurate concentration of ethanoic
acid, 500.0 cm3 of 1.0 00 mol dm-3 CH3COOH
will be directly sourced from the school
laboratory (authorized source) and diluted to
0.500 mol dm-3 CH3COOH. This has to be
controlled to minimize unwanted fluctuation in
the resulting data.
Type of pH The same type and source of phenolphthalein
measurement tool (and pH meter) will be used consistently
throughout the experiment. This has to be
controlled to minimize confusion arising from
different shades and values.
* Other minor fluctuations, such as pressure, may be present; however, due to realistic limitation and practicality, we assume that the
pressure for all replicated experiments is 1ATM, and the fluctuation is negligible.
Safety and environmental precaution
Though this experiment does not deal with extremely harmful chemicals or dangerous apparatus, mild
risks still remains when not used appropriately. Ensure all protections are worn during the course of
the experiment.
Chemicals: ethanoic acid, sodium hydroxide
Ethanoic acid (CH3COOH)4 may cause severe corrosive injury when either ingested. May
cause severe corneal damage in the eye when directly contacted with the eye. Though the
4
Material Safety Data sheet Ethanoic acid. 2001. Chemistry Courses at Iowa State [ONLINE] Available at: http://avogadro.chem.iastate.edu/MSDS/acglac.htm.
[Accessed 6 July 2015].
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