Please answer part C. Thank you. The forensic technician at a crime scene has ju

Question

Please answer part C. Thank you.

The forensic technician at a crime scene has just prepared a luminol stock solution by adding 12.0 g of luminol into a total volume of 75.0 mL of H_2O. What is the molarity of the stock solution of luminol? Express your answer with the appropriate units. Before investigating the scene, the technician must dilute the luminol solution to a concentration of 5.00 times 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. What volume of the stock solution (Part A) would contain the number of moles present in the diluted solution (Part B)? Express your answer with the appropriate units.

Explanation / Answer

Part A :

Molarity , M = ( mass/molar mass) x ( 1000 / Volume in mL)

Given mass of luminol = 12.0 g

Molar mass of luminol, C8H7N3O2 ,= 177.16 g/mol

Volume = 75.0 mL

Plug the values we get , M = ( 12.0 /177.16) x ( 1000/75.0)

                                      = 0.904 M

Part B :

Number of moles , n = Molarity x volume in L

                              = 5.00x10-2 M x 2.00L

                              = 0.10 moles

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