Answer all of the questions below. Part marks will be given where appropriate. Your final answer should have the correct number of significant figures unless noted otherwise.
Copper sulphate pentahydrate CuSO4.5H2O is a blue solution that can be analyzed using AA A set of standards is run and the best fit line for the calibration curve is found to be A=0.624(%w/v) + 0.071
A 15.00mL aliquot of an unknown sample containing CuSO4.5H2O was diluted to a final volume of 200.0mL. Analysis of the sample at a wavelength of 520nm in a 1.00cm cuvette was found to have a %T = 22.4
Calculate the concentration of CuSO4.5H2O (%w/v) in the unknown sample. (3 marks)
- A sample is to be analyzed for it’s caffeine content using HPLC.
A 1.00mL aliquot was transferred into a 100.0mL volumetric flask and was found to have a peak area of 0.229min.
A second 1.00mL aliquot was spiked with 0.500mL of a 84.3ppm Caffeine standard and diluted to a final volume of 100.0mL. Analysis of this sample gave a peak area of 0.463.
Calculate the ppm caffeine in the sample. (3 marks)
3.A solution containing 8.89 ppm of NaMnO4(MM = 141.925 g/mol) has a %T = 26.2 in a 2.00 cm cuvette at 520 nm. Calculate the absorptivity of NaMnO4. (2 marks)
Calculate the molar absorptivity of NaMnO4 . Give your answer to the nearest whole number. (2 marks)
An AE calibration curve for tumeric was fitted to an equation:
I = 0.821 × [tumeric ppm]
In a 25.00 mL volumetric flask, 3.00 mL of an unknown sample was diluted to the mark; the intensity (I) for this sample was measured to be I = 0.132.
To a second 25.00 mL volumetric flask, 3.00 mL of an unknown sample and 1.00 mL of a 15.0 ppm tumeric standard were added and diluted to the mark; the intensity (I) for this sample was measured to be I = 0.921.
- Calculate the %spike recovery for the tumeric analysis. (3 marks)
Are your analysis results valid based on your spike recovery? (1 mark)
- Vitamin A (MM 286.45 g/mol) can be analyzed using an electrochemical technique by a multipoint standard addition.
A 6.00mL aliquot of a carrot juice sample was added to each of six 100.00mL volumetric flasks. To each flask varying amounts of a 111.5ppm Vitamin A standard was added. Each flask was analyzed and a plot of signal (mA) versus Cadded (ppm Vitamin A) was created giving a best fit line of y = 4.9177x + 0.333.
Calculate the ppm of Vitamin A in the carrot juice sample. (3 marks)
Calculate the mass(g) required to prepare 200.0mL of a 200.0ppm Cl- (MM 35.45 g/mol) solution from solid CaCl2 (MM 120.98 g/mol). (3 marks)
A 25.00mL aliquot of the 200.0ppm Cl- stock solution was diluted to 500.0mL. What is the molarity (Cl-) of the prepared working solution? (2 marks)
You need to prepare 100.00mL of a 15.5 ppm Cl standard solution from the above Cl stock solution (200.0 ppm). You have a 25mL buret, a 50mL volumetric flask and the stock solution. How would you prepare the solution? (3 marks)
