Question

Suppose a solution was too concentrated for an accurate reading with the spectrophotometer. The concentrated solution was diluted by placing 1.00 mL of the concentrated solution in 4.00 mL of water. The solution was then placed in the spectrophotometer and an absorbance was obtained and after a few calculations the molar concentration was calculated to be 3.5 × 10–6 M. what was the concentraion of the original solution

Answer 1

Using the law of dilution:

initial Molarity = 3.5x10⁻⁶ M

Initial volume = 4.00 mL

final Molarity = ??

final volume = 1.00 mL

Therefore:

Mi x Vi = Mf x Vf

(3.5x10⁻⁶) x 4.00 = Mf x 1.00

1.4x10⁻⁵ = Mf x 1.00

Mf = 1.4x10⁻⁵ / 1.00 = 

 1.4x10⁻⁵ M