he 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 \rm mL of \rm H_2O.
correct answer is .904 M
To find the concentration of the luminol stock solution, we need to calculate the molarity (M) of the solution.
Step 1: Convert the given mass of luminol to moles.
The molar mass of luminol (C8H7N3O2) is:
C: 12.01 g/mol
H: 1.01 g/mol
N: 14.01 g/mol
O: 16.00 g/mol
To calculate the molar mass of luminol, we add up the atomic masses of its constituent elements:
12.01 x 8 + 1.01 x 7 + 14.01 x 3 + 16.00 x 2 = 177.18 g/mol
Now we can calculate the moles of luminol:
12.0 g / 177.18 g/mol = 0.0678 mol
Step 2: Calculate the volume of the stock solution in liters.
The volume given is in milliliters (mL). We need to convert it to liters.
75.0 mL = 75.0 mL * (1 L / 1000 mL) = 0.075 L
Step 3: Calculate the molarity of the luminol stock solution.
Molarity (M) = moles / volume (in liters)
Molarity = 0.0678 mol / 0.075 L = 0.904 M
Therefore, the concentration of the luminol stock solution is 0.904 M.
To determine the concentration of the luminol stock solution, you need to calculate its molarity (M). Molarity is defined as the number of moles of solute per liter of solution.
First, you need to calculate the number of moles of luminol in the solution. To do this, you will use the formula:
moles = mass / molar mass
The molar mass of luminol (C8H7N3O2) is the sum of the atomic masses of its elements. According to the periodic table:
Carbon (C) has a molar mass of 12.01 g/mol
Hydrogen (H) has a molar mass of 1.01 g/mol
Nitrogen (N) has a molar mass of 14.01 g/mol
Oxygen (O) has a molar mass of 16.00 g/mol
Calculating the molar mass of luminol:
(8 * molar mass of carbon) + (7 * molar mass of hydrogen) + (3 * molar mass of nitrogen) + (2 * molar mass of oxygen)
= (8 * 12.01 g/mol) + (7 * 1.01 g/mol) + (3 * 14.01 g/mol) + (2 * 16.00 g/mol)
= 96.08 g/mol + 7.07 g/mol + 42.03 g/mol + 32.00 g/mol
= 177.18 g/mol
Now that we know the molar mass of luminol, we can calculate the number of moles:
moles = mass / molar mass
= 12.0 g / 177.18 g/mol
= 0.0677 mol
Next, we need to calculate the volume of the solution in liters. As per the given information, the volume of the luminol stock solution is 75.0 mL. To convert mL to L, divide by 1000:
volume = 75.0 mL / 1000
= 0.075 L
Finally, we can calculate the molarity (M) of the solution:
Molarity = moles / volume
= 0.0677 mol / 0.075 L
= 0.90 M
Therefore, the concentration of the luminol stock solution is 0.90 M.
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