A) Determine the concentration in molarity (M) of a crystal violet solution based on a measured absorbance of 0.545
at 590 nm at a path length of 1.0 cm .
B) Based on your determined concentration (in molarity,M), how many milligrams of crystal violet were dissolved in the
2 mL of water used to prepare the sample for the cuvette?
C) What is the ppm concentration? The molar extinction coefficienet is 87,000 M–1cm–1 and the
molecular weight is 407.98 g/mol. The density of water is 1.00 g/mL.
PLEASE HELP!!!! :)
a.
A = ebc
0.545 = 87,000 x 1 x M
Solve for M = approximately 6E-6 but you need to do it more accurately.
b.
M = mols/L
6E-6 = mol/0.002
mols = about 1.25
grams = mols x molar mass = about 5E-6 g = about 5E-3 mg.
c.
5E-6g = 5E-3 mg in 2 mL. Convert that to mg/L to obtain ppm.
THANK YOU!!!!
A) To determine the concentration in molarity (M), we can use the Beer-Lambert Law, which relates absorbance (A), molar absorptivity (ε), concentration (c), and path length (L) as follows:
A = ε * c * L
Rearranging the equation, we can solve for concentration (c):
c = A / (ε * L)
Given:
Absorbance (A) = 0.545
Path length (L) = 1.0 cm
The molar absorptivity (ε) value for crystal violet is not provided. Please provide the molar absorptivity (ε) value so we can proceed with the calculation.
B) Once we have determined the concentration in molarity (M) from part A, we can calculate the number of milligrams of crystal violet dissolved in the 2 mL of water.
To do this, we will use the molar mass of crystal violet to convert concentration from molarity (M) to milligrams (mg).
Given:
Volume (V) = 2 mL
Molar mass (Mw) = 407.98 g/mol
Number of moles (n) = concentration (c) * volume (V)
Mass (m) = number of moles (n) * molar mass (Mw)
C) To calculate the ppm concentration, we need to know the mass of crystal violet dissolved in a specific volume of solution.
Given:
Molar extinction coefficient (ε) = 87,000 M–1cm–1
Molar mass (Mw) = 407.98 g/mol
ppm concentration (ppm) = (mass of solute (mg) / volume of solution (mL)) * 10^6
= (mass of solute (mg) / (volume of solvent (mL) + volume of solute (mL))) * 10^6
Please provide the volume of the solution so we can proceed with the calculation.
Of course! I'd be happy to help you with these questions. Let's break them down one by one:
A) To determine the concentration of the crystal violet solution in molarity (M), we can use the Beer-Lambert Law, which relates the absorbance of a solution to its concentration. The formula is given by:
A = ε * c * l,
where A is the absorbance, ε is the molar extinction coefficient, c is the concentration, and l is the path length. In this case, A (absorbance) is 0.545, ε is 87,000 M–1cm–1, and l (path length) is 1.0 cm.
To calculate the concentration (c) in Molarity, we can rearrange the formula as follows:
c = A / (ε * l).
Substituting the given values:
c = 0.545 / (87,000 M–1cm–1 * 1.0 cm).
Now, you can calculate the numerical value of the concentration in Molarity (M).
B) To determine the number of milligrams of crystal violet dissolved in the 2 mL of water used, we can use the concentration (c) we calculated in the previous step and the formula:
mass = concentration * volume.
In this case, the concentration is already in Molarity (M), and the volume is given as 2 mL. However, we need to convert the volume to liters to match the unit of concentration. There are 1000 mL in 1 L, so 2 mL is equal to 0.002 L.
Substituting the known values into the formula:
mass = concentration * volume,
mass = c * 0.002 L.
Now, you can calculate the mass of crystal violet dissolved in milligrams.
C) To determine the ppm (parts per million) concentration, we need to know the molecular weight of crystal violet. In this case, the molecular weight is given as 407.98 g/mol.
ppm is calculated by the formula:
ppm = (mass of solute / mass of solution) * 10^6.
To find the mass of the solute (crystal violet), we can use the concentration we calculated earlier and the formula:
mass of solute = concentration * volume * molecular weight.
Substituting known values:
mass of solute = c * 0.002 L * 407.98 g/mol.
To calculate the mass of the solution, we can use the density of water, which is given as 1.00 g/mL, and the formula:
mass of solution = volume * density.
Substituting known values:
mass of solution = 0.002 L * 1.00 g/mL.
Now, you can substitute these values into the ppm formula to calculate the ppm concentration of crystal violet.
I hope this helps! Let me know if you have any further questions.