What is the initial concentration of crystal violet solution

Question

What is the initial concentration of crystal violet solution made from adding 4.04 mL of 1.00x10^-5 M CV solution to 3.00 mL of 0.100M NaOH(aq) and diluting with water to make a 25.00 mL solution? Report your answer in μM.

Answer 1

Perhaps the question meant to ask "what is the final concentration of CV since the initial concentration is already provided as 1.00x10^-5 M. If that's the case, then this is a simple dilution problem performed by takining 4.04 ml of 1.00x10^-5 M CV and diluting to final volume of 25.0 ml (the addition of 3 ml of 0.1 M NaOH does not enter into the calculation).

V1M1 = V2M2

V1 = initial volume = 4.04 ml

M1 = initial molarity = 1.00x10^-5 M

V2 = final volume = 25.0 ml

M2 = final molarity = ?

(4.04 ml)(1.00x10^-5 M) = (25.0 ml)(x M)

x = 1.616x10^-6 M

Converting to uM and using 3 sig. figs. the answer is 1.62 uM

If the question is simply asking for the initial concentration of CV in uM units, then the answer would be

1.00x10^-5 M x 1 uM / 1x10^-6 M = 10 uM