Help please??

Given a stock solution of a food dye having a concentration of 1.0 x 10 ^-5 M and an absorbance of 0.700. If a new solution is made by diluting exactly 10.0 mL of the solution with exactly 80.2 mL of distilled water, what should the absorbance of the new solution be?

Question

Help please??

Given a stock solution of a food dye having a concentration of 1.0 x 10 ^-5 M and an absorbance of 0.700. If a new solution is made by diluting exactly 10.0 mL of the solution with exactly 80.2 mL of distilled water, what should the absorbance of the new solution be?

jfraser · Answer

use Beer's Law
$$A = \epsilon *b*C$$ the first set of conditions allows you to find e. In the second set, use the e from the first set to find C.

jfraser · Answer

^cancel that. Use the new concentration info to find the new A.

vane11 · Answer

So would it be this? .700 = 10 x 80.2 x (1x10^-5)

jfraser · Answer

no. you're mixing both sets of solutions together. Have you heard of Beer's Law before?

vane11 · Answer

No this is my first time and I'm reading it off from a book so it's a bit confusing

aaronq · Answer

Do you know what each of the variables in the beer-lambert law represents?

you're first using the values given (1.0 x 10 ^-5 M and an absorbance of 0.700) to find the molar absorptivity coefficient, epsilon.

Then you have to find the new concentration of the solution 
>diluted 10 mL of the 1.0 x 10 ^-5 M solution with 80.2 mL distilled water

Then use the new concentration and the epsilon you found previously to find the absorbance.

Hint: the path length of the cuvette is assumed to be 1 cm (as it most often is).