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Essay of 22 pages for the course unit 19 at PEARSON (UNIT 19 ASSIGNMENT)
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Assignment B Unit 19
P3: Demonstrate accurately the concentration of solutions using the
Beer-Lambert Law
Task 1: Determining glucose concentration in lemonade
Methodology -
1. I prepared samples of lemonade that had different concentrations of
glucose.
2. I used a colorimeter to measure absorbance of every sample at a
precise wavelength.
3. I added a coloring reagent to every sample to make the color change
more obvious.
4. Using a colorimeter I re-measured the absorbance.
5. I made a standard curve by the use of known concentrations of
glucose.
Results -
A linear connection was found between the concentration of glucose
and absorbance.
The samples of lemonade showed differing concentrations of glucose,
higher absorbance implied higher content of glucose.
Using the standard curve to precisely determine the glucose
concentration in every sample.
Task 3: Measuring nitrate concentration in soil solution
Methodology -
1. From multiple locations, I collected samples of soil.
2. Using a suitable solvent, I took out soil solutions – extracted.
3. To measure the absorbance of the solution at a specific wavelength of
UV, I used an UV spectrometer, associated with nitrate.
4. A series of standard nitrate solutions was prepared to make a
calibration curve.
1
, 5. I compared the absorbance of the soil solution with the calibration
curve to make sure of the nitrate concentration.
Results -
I detected differing concentrations of nitrate in the samples of soil that
I got from different locations
Between the concentration of nitrate and absorbance I found a linear
relationship
I identified higher concentrations of nitrate in some samples of soil in
comparison to other ones, this indicated possible differences in soil
fertility or pollution levels.
PARACETAMOL
The absorption of a solution stays directly proportional and constant with the
concentration is what the Beer Lamberts Law states. This implies that for
both IR spectrums the concentration should be constant. Between 3200cm-1
and 3400cm-1 is where the peaks occur in the diagram above for both of
them, the impure and recrystallized paracetamol, the recrystallised peak is
larger than the impure one. From this we can tell that the one that is
recrystallized contains more paracetamol than the one that is impure. The
transmission of the paracetamol that is recrystallized has bigger peaks which
means it must have a higher concentration in comparison to the impure one
since that has smaller peaks, in the fingerprint section in both graphs. The
shorter the peak is the lower the concentration of the product it has. This
returns to the theory of the Beer Lamberts Law that says that concentration
2
, and absorption are directly proportional. In this instance it is proven that the
higher the absorption for the paracetamol that is recrystallized the higher
the concentration. Also it means its more concentrated with paracetamol
which means it is more pure than the impure one. The spectrum, has shorter
peaks which means that it has a lower concentration, on the left has a
transmission which is high. If the Beer Lambert Law was to be applied here,
the lower the absorption the lesser the concentration of the product it has
since the levels of absorption is directly proportional to it.
In conclusion, the paracetamol that is impure in the left side of the graph has
a low absorption and the paracetamol that is recrystallized that is more pure
if it was to be compared to the other, gets represented by the graph on the
right-hand side since its absorption is higher.
Brass Experiment
Procedure
Preparation of brass solution, done by teacher, scaled up by x10
1. Precisely weighing out around 0.3g of brass into a 25cm3 beaker
2. Add 5cm3 of 5M nitric acid by using a plastic pipette into a beaker,
inside the fume cupboard.
3. Using a hot plate with a temperature of about 60 degrees celsius,
warm the mixture of reaction
4. Put the beaker to aside to let it cool down once all the brass has
dissolved and you have stopped heating it.
5. Using a 10cm3 volumetric flask, move the solution into it, then add a
couple drops of water to rinse out the beaker, then move the washings
into a flask. Fill up the flask to the line by adding more water. Invert
the flask after putting on a stopper and mix it a couple of times.
Preparation of Standards
By using burettes, prepare a series of diluted standard solutions of copper (ii)
into test tubes.
- Picking the right filter
1. Using the first filter, set up the colorimeter. Add in the blank (water).
Change the sensitivity control to end up with 0% and 100%
transmission.
2. With the solution with the most concentrated and then measure the %
absorption.
3
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