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Colorimetry (Equipment (visible light, light from a suitable source (Use…
Colorimetry
Equipment
Place the solution in a cuvette and place in the colorimeter
visible light, light from a suitable source
Use distilled water as a control
If the solution is too dense, carry out a serial dilution, changing the concentration of the solution
Plot a graph for each and plot a graph of transmittance/absorbance against concentration, plot a line of best fit and read off the concentration for the absorbance/transmittance
photocell
It can measure transmittance or absorbance
Results
Absorbance
Negative gradient
Opposite Colour Light
Transmittance
Positive gradient
Same Colour Light
Determining Order
Linear: zeroth order as the rate is independent of the concentration of the reactants.
Polynomial: first/second order.
At 0,0 you can use a sample of distilled water, and compare the other results to it, as a reference
Question 4!!!!!!!!
https://qualifications.pearson.com/content/dam/pdf/A%20Level/Chemistry/2015/Specification%20and%20sample%20assessments/A-level-Chemistry-2015-SAMs.pdf
Filter
You make the filter the opposite colour of the solution being tested.
This would filter out all the other colours apart from the colour. For example, if an orange filter is used, all other colours like blue, green, red ect is all prevented from going through, apart from orange. So the light becomes orange.
This would allow the colour most absorbed by the solution to pass through as it is the opposite on the colour wheel.
http://www.ocr.org.uk/Images/63300-question-paper-unit-f212-molecules-biodiversity-food-and-health-instructions-to-candidates.pdf
(Question 3D)
http://www.ocr.org.uk/Images/59656-mark-scheme-june.pdf
(Answer on page 20) --------------------------------------------------------- Bit of context for the question: you're testing the concentration of sugar in a sugar solution. Another reagent is added to the solution, in the presence of sugar, the reagent turns blue. So you're using a colorimeter to test the conc of the sugar.
Colour
wheel
If an aqueous transition metal ion is intensely coloured, its concentration can be measured directly e.g. manganese concentration can be measured if it is oxidised to the deep purple manganate(VII) ion, MnO4–.
Calibration curve
Plot of curve of absorbance against known concentrations of solution and interpolate between the points that have been plotted
QUESTIONS
Questions
Question 4)b)iii
Question 5
Question 2)f
.QP17.pdf)
How does it work?
