Question

1. The observation that the absorbance is linearly proportional to the concentration of dye is a statement of which law?

2. For this question, note that you diluted your prepared drink mix 1:10 before you obtained absorbance values, and therefore your calculated concentration of each dye is 1/10 that of the prepared drink mix. You calculated that the concentration of yellow food dye in the cuvette is 0.0141 mM.  Given that the molecular weight of the yellow 5 dye is equal to 534.36 g/mol. How many grams of yellow 5 food dye were in the 0.235 L solution of drink mix? (Remember that molarity = moles / L and that molecular weight = mass / moles). Choose the closest answer.

3. Given that the mass of the red dye in 0.5 g of prepared drink mix is equal to 0.00089 g, what percent mass does this represent? (Percent mass = (mass of dye / mass of powder ) * 100%)  

4. Given that the mass of the yellow dye in 0.5 g of prepared drink mix is equal to 0.0018 g, what percent mass does this represent? (Percent mass = (mass of dye / mass of powder ) * 100%)

5.The concentration of red food dye in the prepared drink mix can be calculated from Beer's law (absorbance = path length (1 cm) * extinction coefficient * concentration). Using the extinction coefficient for the red dye calculated in experiment 2 and the absorbance of the drink mix at 500 nm, calculate the concentration of red food dye. Choose the closest answer.

6.For this question, note that you diluted your prepared drink mix 1:10 before you obtained absorbance values, and therefore your calculated concentration of each dye is 1/10 that of the prepared drink mix. You calculated that the concentration of the red food dye in the cuvette is 0.0089 mM. Given that the molecular weight of the red 40 dye is equal to 496.42 g/mol. How many grams of red 40 food dye were in the 0.235 L solution of drink mix? (Remember that molarity = moles / L and that molecular weight = mass / moles). Choose the closest answer.

7.The concentration of yellow food dye in the prepared drink mix can be calculated from Beer's law (absorbance = path length (1 cm) * extinction coefficient * concentration). Using the extinction coefficient for the yellow dye calculated in experiment 2 and the absorbance of the drink mix at 420 nm, calculate the concentration of yellow food dye. Choose the closest answer.

8.The equation for a straight line representing the absorbance of the red dye at the peak absorbance wavelength as a function of the concentration of the red dye is y = 27320x +0. The slope of the line gives the extinction coefficient. What is the molar extinction coefficient for the red dye?

Answer 1

1. The observation that the absorbance is linearly proportional to the concentration of dye is a statement of which law?

Solution: Beer Lambert’s law

1. For this question, note that you diluted your prepared drink mix 1:10 before you obtained absorbance values, and therefore your calculated concentration of each dye is 1/10 that of the prepared drink mix. You calculated that the concentration of yellow food dye in the cuvette is 0.0141 mM.  Given that the molecular weight of the yellow 5 dye is equal to 534.36 g/mol. How many grams of yellow 5 food dye were in the 0.235 L solution of drink mix? (Remember that molarity = moles / L and that molecular weight = mass / moles). Choose the closest answer.

Solution:

The concentration of drink mix = 10 X diluted dye

The concentration of drink mix = 10 X 0.0141mM = 0.141 milli Molar

The strength (g / L) = Concentration X molecular weight

                                = 0.141mM X 534.36 g / L = 75.34 mg / L

So mass in 0.235 L = 75.34 X 0.235 mgrams = 17.71 mgrams

1. Given that the mass of the red dye in 0.5 g of prepared drink mix is equal to 0.00089 g, what percent mass does this represent? (Percent mass = (mass of dye / mass of powder ) * 100%)  

Solution:

Mass = 0.00089grams / 0.5grams of drink

Percentage = Mass of dye X 100 / total mass of drink = 0.00089 X 100 / 0.5 = 0.178%

1. Given that the mass of the yellow dye in 0.5 g of prepared drink mix is equal to 0.0018 g, what percent mass does this represent? (Percent mass = (mass of dye / mass of powder ) * 100%)

Solution:

Mass % = 0.0018 X 100 / 0.5 = 0.36%

5.The concentration of red food dye in the prepared drink mix can be calculated from Beer's law (absorbance = path length (1 cm) * extinction coefficient * concentration). Using the extinction coefficient for the red dye calculated in experiment 2 and the absorbance of the drink mix at 500 nm, calculate the concentration of red food dye. Choose the closest answer.

Extinction coffecient not given

6.For this question, note that you diluted your prepared drink mix 1:10 before you obtained absorbance values, and therefore your calculated concentration of each dye is 1/10 that of the prepared drink mix. You calculated that the concentration of the red food dye in the cuvette is 0.0089 mM. Given that the molecular weight of the red 40 dye is equal to 496.42 g/mol. How many grams of red 40 food dye were in the 0.235 L solution of drink mix? (Remember that molarity = moles / L and that molecular weight = mass / moles). Choose the closest answer.

Solution:

The concentration of drink mix = 10 X concentration of dye

The concentration of drink mix = 10 X 0.0089mM = 0.089mM

Mass of dye in one litre = Concentration X molecular weight

                                      = 0.089mM X 496.42 = 44.18mg / L

Mass in 0.235L = 44.18mg / L X 0.235 L = 10.38mg

7.The concentration of yellow food dye in the prepared drink mix can be calculated from Beer's law (absorbance = path length (1 cm) * extinction coefficient * concentration). Using the extinction coefficient for the yellow dye calculated in experiment 2 and the absorbance of the drink mix at 420 nm, calculate the concentration of yellow food dye. Choose the closest answer.

Extinction coefficient not given

8.The equation for a straight line representing the absorbance of the red dye at the peak absorbance wavelength as a function of the concentration of the red dye is y = 27320x +0. The slope of the line gives the extinction coefficient. What is the molar extinction coefficient for the red dye?

The extinction coefficient = 27320 [If it is mass extinction coeffeceint] as we don’t know the units of concentration plotted against absorbance

Molar extinction coefficient = Mass extinction coefficient X Molar mass

= 27320 X 496.42 = 1.356 X 10^7