Question

You have been given a jar of red fruit punch and been asked to determine the concentration of red dye in the fruit punch. You obtain a stock solution of this red dye and it has a concentration of 0.00243 M (in the lab room, the stock solution is found in the hood). You take 10.0 mL of this stock solution and dilute it to 100.0 mL. You call this your standard solution. Using a colorimeter, you determine that the red dye standard absorbs green light (the complementary color) with an absorbance value of 0.65. Complete Table 1 with information regarding the standard solution Table 1: Analysis of Standard Standard Concentration of red dye in stock soln (M) Absorbance of your standard solution Concentration of your standard solution (M) Ratio of absorbance/conc. of standard

Answer 1

Table 1: From the data given:

A) Concentration of red dye in stock solution= 0.00243

B) Absorbance of standard solution = 0.65

C) Concentration of Standard solution = 0.000243

Solution: We have been given the concentration of the stock solution and provided data that there is a 10 fold dilution. Hence concentration of the standard can be found out using the following formula: C₁V_1(stock)=C₂V_2(standard)

Were, C₁ and C₂ correspond to the concentration of stock and standard respectively - C₁= 0.00243M and C₂ is unknown= x.

V₁ is the volume of stock taken= 10ml, V₂ is the total volume of the standard= 100ml.

Therefore using the formula: 0.00243*10= 100*x

x= (0.00243*10)/ 100= 0.000243M

D) Ratio of absorbance/ Concentration of standard = 0.65/ 0.000243= 2674.89

Table B: From the data given:

A) Absorbance of original solution= 2.91

B) Absorbance of serial dilution 1= 1.10

C) Absorbance of serial dilution 2= 0.60

F) red dye concentration of original solution= 0.00243M

E) red dye concentration of serial dilution 1= 0.000486

Solution: Using the following formula: C₁V_1(stock)=C₂V_2(dilution)

C₁ and C₂ correspond to the concentration of stock and first dilution respectively - C₁= 0.00243M and C₂ is unknown= x.

V₁ is the volume of stock taken= 20ml, V₂ is the total volume of the standard= 100ml.

Therefore using the formula: 0.00243*20= 100*x

x= (0.00243*20)/ 100= 0.000486M

D) Red dye concentration of serial dilution 2= 0.0000972M

Solution: Using the following formula: C₁V_{1(dilution 1)}=C₂V_{2(dilution 2)}

C₁ and C₂ correspond to the concentration of stock and first dilution respectively - C₁= 0.000486M and C₂ is unknown= x.

V₁ is the volume of stock taken= 20ml, V₂ is the total volume of the standard= 100ml.

Therefore using the formula: 0.000486*20= 100*x

x= (0.000486*20)/ 100= 0.0000972M