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The iron content in multivitamin tablets was determined using atomic absorption spectroscopy - VCE - SSCE Chemistry - Question 6 - 2012 - Paper 1
Question 6
The iron content in multivitamin tablets was determined using atomic absorption spectroscopy. The absorbances of four standards were measured. Three multivitamin ta... show full transcript
Worked Solution & Example Answer:The iron content in multivitamin tablets was determined using atomic absorption spectroscopy - VCE - SSCE Chemistry - Question 6 - 2012 - Paper 1
Step 1
i. Use the grid below to construct a calibration graph of the absorbances of the standard solutions.
Answer
To construct the calibration graph, first, plot the absorbance values against the corresponding concentrations of the standard solutions:
- Place the concentration (mg/L) on the x-axis and the absorbance on the y-axis.
- For each standard solution, identify the point based on its concentration and absorbance:
- (0, 0.06)
- (100, 0.16)
- (200, 0.25)
- (300, 0.36)
- (400, 0.46)
- After plotting the points, draw a line of best fit through them, which should be approximately a straight line indicating a linear relationship between concentration and absorbance.
Step 2
ii. Determine the average iron content, in milligrams, of the multivitamin tablets.
Answer
To determine the average iron content from the absorbance values of the tablets, first interpolate the absorbance values for each tablet:
- For Tablet 1 with an absorbance of 0.39, using the calibration curve (estimation from graph), it corresponds roughly to a concentration of 300 mg/L.
- For Tablet 2 with an absorbance of 0.42, the corresponding concentration is approximately 360 mg/L.
- For Tablet 3 with an absorbance of 0.45, the concentration is around 380 mg/L.
Then, calculate the average: ext{Average Concentration} = rac{300 + 360 + 380}{3} = rac{1040}{3} ext{ mg/L} \\ = 346.67 ext{ mg/L}
Then, assuming the original solution was diluted to 100 mL, multiply the average concentration by this factor to find the total iron content in milligrams:
Step 3
Step 4
Step 5
v. How does this part of the electromagnetic spectrum interact with matter? What information does this spectroscopic technique provide?
Answer
In Atomic Absorption Spectroscopy (AAS), the visible part of the spectrum interacts with electrons in atoms, causing them to move to higher energy levels upon absorption.
This technique provides information about the concentration of the absorbing species in a sample, allowing for the determination of the amount of iron, in this case, present in the multivitamin tablets.