The forensic technician at a crime scene has just prepared a luminol stock solution by adding 14.0 g of luminol into a total volume of 75.0 mL of H20.

Question

What is the molarity of the stock solution of luminol?

Answer 1

To calculate the molarity of the stock solution, we first need to determine the number of moles of luminol in the solution.

Step 1: Calculate the molar mass of luminol (C8H7N3O2):
C = 12.01 g/mol
H = 1.01 g/mol
N = 14.01 g/mol
O = 16.00 g/mol

Molar mass of luminol = (8 x 12.01) + (7 x 1.01) + (3 x 14.01) + (2 x 16) = 249.21 g/mol

Step 2: Calculate the number of moles of luminol in 14.0 g:
Number of moles = mass / molar mass
Number of moles = 14.0 g / 249.21 g/mol = 0.056 mol

Step 3: Calculate the volume of the solution in liters:
Volume of solution = 75.0 mL = 75.0 / 1000 = 0.075 L

Step 4: Calculate the molarity of the stock solution:
Molarity = number of moles / volume of solution
Molarity = 0.056 mol / 0.075 L = 0.747 M

Therefore, the molarity of the stock solution of luminol is 0.747 M.