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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 best wavelength for measuring the concentration of Red No. 2 dye, we need to look for a wavelength where this dye absorbs light significantly compared to the other dyes.
From the provided graph, Red No. 2 shows a peak absorbance around 600 nm. At this wavelength, the absorption due to Red No. 2 is pronounced, which allows for more accurate determination against potential interference from Blue No. 1 and Yellow No. 4.
Among the options provided:
- 430 nm and 500 nm show lower absorption for Red No. 2.
- 540 nm falls within the absorption range of Blue No. 1, which may cause interference.
- 620 nm is the best option as it maximizes the absorbance of Red No. 2 while minimizing interference from the other two dyes.
Thus, the best choice is 620 nm, which corresponds to option D in the question.