Question

The forensic technician at a crime scene has just prepared a luminol stock solution by adding 20.0 g of luminol into a total volume of 75.0 mL of H₂O.

What is the molarity of the stock solution of luminol?

Express your answer with the appropriate units.molarity of luminol solution =1.51M

Part B

Before investigating the scene, the technician must dilute the luminol solution to a concentration of 2.00×10⁻² M. The diluted solutionis 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.moles of luminol =4.00×10⁻² mol

Part C

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.

volume =
I want part c

Answer 1

A.

$$ \begin{aligned} \text { molarity } &=\frac{\mathrm{n}_{\text {moles }}}{\text { Volume }_{\mathrm{L}}} \quad 1 \mathrm{~L}=1000 \mathrm{ml} . \\ &=\frac{\mathrm{w}_{\text {Luminol }}}{\mathrm{mol} . \mathrm{wt}_{\text {luminol }}} \times \frac{1000}{\text { Volume }_{\mathrm{ml}}} \\ &=\frac{20.0 \mathrm{~g}}{177.16 \mathrm{~g} \mathrm{~mol}^{-1}} \times \frac{1000}{75 \mathrm{ml}} \\ &=1.505 \mathrm{M} . \end{aligned} $$

Generally, Luminol should not readily dissolve in sodium borate dissolved in half a liter of water thoroughly, then sodium carbonate and Luminol solids are added into the solution. Finally, the solution allowed to settle down the chemical undissolved then discards solid chemicals. The solution

used as a standard Luminol solution.

B.

Answer 2

4.00x 10^-2 = 0.04 moles
1.51 moles / L
0.04 / 1.51 = 0.02649 L, or 26.49 mL

Please Rate A+ and message for any additional help :)

Answer 3

Part (C)
mole in part (B) = 4e-2 mol
concentration in part (A) = 1.51 M

mole = concentration x volume
4e-2 = 1.51 x volume
volume = 2.65e-2 L