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The graph shows the absorption spectra of three food dyes: Blue No - VCE - SSCE Chemistry - Question 9 - 2010 - Paper 1
Question 9
The graph shows the absorption spectra of three food dyes: Blue No. 1, Red No. 2 and Yellow No. 4. Which one of the following is the best wavelength to determine th... show full transcript
Worked Solution & Example Answer:The graph shows the absorption spectra of three food dyes: Blue No - VCE - SSCE Chemistry - Question 9 - 2010 - Paper 1
Step 1
Which one of the following is the best wavelength to determine the concentration of Red No. 2 dye in a solution containing a mixture of all three dyes?
Answer
To determine the concentration of Red No. 2 dye effectively, we need to select a wavelength where the absorbance of Red No. 2 is high while the absorbance of the other dyes (Blue No. 1 and Yellow No. 4) is low.
- Examine the graph: At approximately 500 nm, the absorbance of Red No. 2 is significantly higher than that of Yellow No. 4, indicating that this wavelength would allow for a more accurate measurement of Red No. 2 concentration.
- Check other wavelengths:
- At 430 nm, both Blue No. 1 and Red No. 2 show absorbance, which may cause interference.
- At 540 nm and 620 nm, the absorbance of Red No. 2 is lower compared to 500 nm, making it less effective for measurement.
Therefore, the best wavelength to determine the concentration of Red No. 2 dye in the presence of other dyes is 500 nm.