Question

A.Write a brief procedure outling how would you prepare 250mL of a 0.150M solution of a CoCl2 from solid CoCl2 and distilled water

b. Using the solution from part a and distilled water, how would you prepare 100ml of a 0.0600 M solution of CoCl2

C. What absorbance would you expect from the solution from part b at the wavelength of maximum sensitivity?

Answer 1

a. How many mols do you want? That's M x L = 0.150 x 0.250 = ?
Then mols = grams/molar mass. You know molar mass and mols, solve for grams CoCl2. Add that many g CoCl2 to a 250 mL volumetric flask, add a little water, swirl until dissolved, make to the mark with distilled H2O and mix thoroughly.

b. Use mLa x Ma = mLb x Mb

c. You don't have enough information to answer c. The absorbance depends upon the concn of the CoCl2 and you must have some data that gives an A for some C. Whatever that data is, you plug it into this formula.
A1*C2 = A2*C1
A = absorbance of solution 1 and 2
C = concn of solution 1 and 2

Answer 2

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