Question

The chemical 5-amino-2,3-dihydro-1,4-phthalazinedione, better known as luminol, is used by forensic scientists in analyzing crime scenes for the presence of washed-away blood. Luminol is so sensitive that it can detect blood that has been diluted 10,000 times. A basic solution of luminol is often sprayed onto surfaces that are suspected of containing minute amounts of blood. Luminol has a molecular weight of 177 g/mol. Now consider that the technician made a mistake and needs to prepare a new stock solution. The new stock solution prepared is 1.02 M in luminol. If the technician wishes to prepare 1.99 L of a 4.00 x 10^-2 M solution of luminiol, what volume of the 1.02 M luminol solution could he dilute down to prepare the 1.99 L of 4.00 x 10^-2 M luminol solution?

Answer 1

initial molarity = C1 = 1.02 M

intial volume = V1

final molarity = C2 = 4.00 x 10^-2 M

final volume = V2 = 1.99 L

dilution formula :   C1 V1 = C2 V2

                           1.02 x V1 = 4.00 x 10^-2 x 1.99

                            V1 = 0.0780 L

volume of stock needed = 0.0780 L = 78.0 mL