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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. The absorbance of each... 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, plot the absorbance values on the y-axis against the concentration (mg/L) on the x-axis using the provided data. Begin by marking the points for each standard solution:
- (0, 0.06)
- (100, 0.16)
- (200, 0.25)
- (300, 0.36)
- (400, 0.46)
Then, draw a best-fit line through these points, extending it back to zero concentration to demonstrate the linear relationship between absorbance and concentration.
Step 2
ii. Determine the average iron content, in milligrams, of the multivitamin tablets.
Answer
To calculate the average iron content, first refer to the absorbance values measured for each multivitamin tablet:
- Tablet 1: 0.39
- Tablet 2: 0.42
- Tablet 3: 0.45
Using the calibration graph drawn in part i, determine the corresponding concentrations from the graph for each tablet's absorbance. For example:
- For Tablet 1 with an absorbance of 0.39, the corresponding concentration might be approximately 120 mg/L (consult the calibration line for accuracy).
- For Tablet 2 with an absorbance of 0.42, the concentration could be around 130 mg/L.
- For Tablet 3 with an absorbance of 0.45, the concentration may be about 140 mg/L.
Now, calculate the average iron content by averaging these concentrations:
ext{Average} = rac{120 + 130 + 140}{3} = 130 ext{ mg/L}
To convert from mg/L to milligrams per tablet, multiply the average by the volume of the tablet solution analyzed in liters (0.100 L):
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, the visible spectrum causes electrons in the atoms to move to higher energy levels when they absorb photons. This interaction allows for the quantification of the concentration of elements present in the sample. The primary information provided by this technique is the concentration of specific metal ions in the sample, which can be directly correlated with their absorbance values.