1. Why are certain molecules chosen for food dyes? Look at the chemical structur
ID: 485948 • Letter: 1
Question
1. Why are certain molecules chosen for food dyes? Look at the chemical structures in Table 1 and explain how and why these molecules make good dyes.
2. What was the color of the sample that gave the absorbance spectrum in Figure 4a?
3.) A sample of substance Z needs to be characterized. A standard curve for substance Z was constructed by taking absorbance measurements at 504 nm of a series of solutions of Z with known concentration. Use the equation of the standard curve, generated by the linear regression of the data, to calculate the concentration of the unknown sample of Z whose absorbance is 0.355 (A504 = 0.355). Show your work and include units and the appropriate number of significant figures. N.B.: Based on the scale of the x-axis, the first interval is 0.300 x 102.
4.) A 1.500 mL aliquot of the substance Z sample used in Question 4 was mixed with 3.500 mL of water. What is the concentration of this new sample? What A504 would you expect for this sample?
5.)
A 1.500 mL aliquot of the substance Z sample used in Question 4 was mixed with 3.500 mL of water.
What is the concentration of this new sample? What A504 would you expect for this sample?
6.)
A different sample of substance Z gave an initial absorbance much greater than 1.000. Several dilutions were performed before an absorbance reading between 0.100 and 1.000 could be obtained. From the dilutions and data below, determine the initial concentration of the sample. Use the equation of the standard curve in Question 4.
The dilutions were as follows:
10.000 mL of the initial sample was mixed with 10.000 mL of deionized water.
10.000 mL of the dilute sample from (a) was mixed with 10.000 mL of deionized water.
5.000 mL of the dilute sample from (b) was mixed with 10.000 mL of deionized water.
The solution in (c) gave an absorbance reading (at 504 nm) of 0.374.
Explanation / Answer
1. Only certain molecules such as dye, pigment or substance that imparts color when it is added to food or drink are chosen as food dyes.
The molecules that make good dyes contain aromatic and conjugated structural systems for efficient absorption of light in the visible region, they are deeply colored.
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