Question

A) The forensic technician at a crime scene has just prepared a luminol stock solution by adding 11.0 g of luminol into a total volume of 75.0 mL of H2O. What is the molarity of the stock solution of luminol?

B) Before investigating the scene, the technician must dilute the luminol solution to a concentration of 5.00×10−2 M. The diluted solution is then placed in a spray bottle for application on the desired surfaces. How many moles of luminol are present in 2.00 L of the diluted spray? Express your answer with the appropriate units. Express your answer with the appropriate units.

Answer 1

A) mass of lumino C8H7N3O2 = 11.0 g

     molar mass of luminol = 177.16 g/mol

moles = mass / molar mass

            = 11.0 / 177.16

            = 0.0621

volume = 75 mL = 75 x 10^-3 L

molarity = moles / volume

             = 0.0621 / 75 x 10^-3

             = 0.828 M

molarity   = 0.828 M

B)

moles = molarity x volume

           = 5 x 10^-2 x 2.00

            = 0.100