BTEC Applied Science Unit 2A- Titration and Colorimetry (Distinction)
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Course
Unit 2
Institution
PEARSON (PEARSON)
Exemplar assignment for the first assignment of Unit 2 in BTEC Applied Science, Unit 2A, which is about carrying out two titrations and colorimetry of copper sulphate solution. If you take anything from this assignment, please put it in your own words otherwise it will count as plagiarism! Also do ...
Unit 2: Practical Scientific Procedures and Techniques
Learning aim A: Undertake titration and colorimetry to determine the
concentration of solutions
Keeping up the Standards
As part of my induction period as a technician’s apprentice at a sixth form college, I was required to
carry out two different titrations to determine the concentration of solutions. I also undertook
colorimetry to determine the concentration of copper sulfate solution.
What is titration and how is it used in industry?
A titration is defined as determining the concentration of an unknown solution using a solution of a
known concentration. It is primarily used in industrial laboratories [1] as a quantitative analytical tool
but also used in various other fields and industries such as environmental management, wastewater
treatment, food processing and pharmaceutical manufacturing. The most common method of
titration is known as an acid-base titration, also known as a neutralisation titration, where the
objective is to produce a neutral solution [2]. This was the titration that I was required to carry out as
part of this assignment. Further titration methods also include complexion titrations, precipitation
titrations, redox titrations and weak polyprotic acid titrations. [2]
What is colorimetry and how is it used in industry?
Like with titration, colorimetry is also used to determine the concentration of solutions. Colorimetry
is a scientific technique that uses the Beer-Lambert law to determine the concentration of coloured
compounds in solutions. The Beer-Lambert law states that the concentration of a solute is directly
proportional to its absorbance [3]. Colorimetry is carried out using a colorimeter, which measures
how much light a solution can absorb.
Making a standard solution of sodium carbonate:
Risk assessment
Risk Hazard Precautions Size of risk What to do in the event of
an accident
Sodium carbonate Can cause serious eye Wear eye Low If it comes into contact with eyes,
irritation. protection irrigate the eye with gently-
As sodium carbonate is an running tap water for at least 20
anhydrous solid, it presents minutes [4]
a bigger risk because it is
finely powdered [4]
Before carrying out the titration, I prepared 250 cm 3 of a 0.1 dm-3 standard solution of sodium
carbonate. In order for me to do this, I calculated the mass of sodium carbonate required to make
the standard solution.
1
,Unit 2: Practical Scientific Procedures and Techniques
Learning aim A: Undertake titration and colorimetry to determine the
concentration of solutions
Calculating the mass of sodium carbonate to be used for making the standard solution
The equation, number of moles = mass x relative formula mass, was used to work out the mass
needed for the standard solution. I converted 250 cm 3 into dm-3, which was 0.025 and worked out
the relative formula mass of sodium carbonate, which was 106. I then multiplied this by 0.025 and
worked out that a mass of 2.65g of sodium carbonate was needed to make the standard solution.
Equipment
● Weighing boat
● Balance
● Distilled water
● 2.65g of sodium carbonate
● Beaker
● Stirring rod
● Volumetric flask
Method
1. Use a weighing boat to weigh out 2.65g of sodium carbonate in exact balance.
2. Fill a 250 cm3 beaker to the top with the sodium carbonate. Rinse the weighing boat with
distilled water to make sure all of the solute has been transferred.
3. Use a stirring rod to ensure that all of the solute has dissolved. Add 150cm 3 of distilled water
to the beaker.
4. Fill a volumetric flask with 250 cm3 of the solution.
5. Rinse the stirring rod and beaker once more with distilled water before transferring them to
the volumetric flask.
6. Fill the volumetric flask with distilled water until it nearly reaches the graduation line.
7. Drop by drop, carefully add water until the meniscus's bottom touches the graduation line.
8. Add a stopper on the top and invert the flask to make sure the solution is mixed well.
Evaluation
I did not have many problems making the standard solution; I ensured that the measurements were
accurate by calibrating the balance and my attempt with making it went well. There were a few
issues in getting the balance to reset to 0g which resulted in me accidentally using the wrong mass of
sodium carbonate and being off by 1-2g. I was able to resolve this by using another balance which
was working accurately.
Using titration to accurately determine the
concentration of hydrochloric acid
Risk assessment
Risk Hazard Precautions Size of risk What to do in the event of
2
, Unit 2: Practical Scientific Procedures and Techniques
Learning aim A: Undertake titration and colorimetry to determine the
concentration of solutions
an accident
Dilute hydrochloric Not classified as Use the lowest Low If spilt on the skin, use a dry cloth
acid hazardous but dilute concentration possible. or paper towel to wipe as much
acid may still cause Use the smallest liquid off the skin as possible.
harm to the eyes or volume possible. Wear Irrigate the affected area with
the skin. [5] eye protection. [5] gently-running tap water for at
least 20 minutes. If it comes into
contact with eyes, irrigate the
eye with gently running tap water
for at least 20 minutes. [5]
Glassware Could break Keep away from the Low If broken, do not touch and
edge of the workspace inform your teacher
Running burette tap Could cause spillages When not in use, turn Low Clean spillage.
the burette tap If acid comes into contact with
horizontally to stop acid skin, wash skin with water
from running
In this titration, I used a standard solution of sodium carbonate to work out the concentration of
hydrochloric acid. For each volume of hydrochloric acid, I recorded the pH of the solution and
worked out a mean pH from my concordant results.
Word equation:
Sodium carbonate + Hydrochloric acid → Sodium chloride + Carbon dioxide + Water
Balanced symbol equation:
Na2CO3 (aq) + 2HCl (aq)→ 2 NaCl (aq) + CO2 (g) + H2O (l)
Equipment
- Burette
- Clamp and stand
- Graduated pipette
- Pipette filler
- pH metre
- Conical flask
- Beaker
- Distilled water
- Hydrochloric acid of an unknown concentration
- Standard solution of sodium carbonate
- Funnel
Before I carried out the titration, I calibrated the pH metre with distilled water using the method
below. This was so that imprecise measurements could be avoided when carrying out the titration.
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