A sample weighing 1.25 mg containing a certain compound M (FW 292.16 g/mol) was dissolved in
solvent in a 5.00 mL volumetric flask. A 1.00 mL aliquot was drawn up, placed in a 10.00 mL volumetric and
diluted to the mark with solvent. The absorbance of this solution at 340 nm was 0.427 in a 1.00 cm
cuvette. The molar absorptivity at 340 nm for the compound is 6130 M�]1 cm�]1.
(a) Calculate the concentration of compound M in the 5 mL volumetric flask.
(b) Calculate the percent purity of the compound.
Absorbance = ecl
0.427 = 6130*c*1
Solve for c in mols/L. This the concentration in the 10.00 mL cuvette. The concentration in mols/L in the 5.00 cuvette is 10x that
grams is c in mols/L x molar mass = ? and that is the concn in g/L. You had 5 mL cuvette; therefore, grams in the 5.00 cuvette will be ?grams in 1L x (5/1000) = ? and that is answer for A (in grams). I would change that to mg. .
B. is [(ans for A in mg/1.25)]*100 = ? I'm guessing about 80% purity.
absorbance = ec
To find the concentration of compound M in the 5 mL volumetric flask, we can use the Beer-Lambert Law equation:
A = ε * c * L
Where:
A = Absorbance (0.427 in this case)
ε = Molar absorptivity (6130 M^(-1) cm^(-1))
c = Concentration of the compound in mol/L (unknown)
L = Path length (1.00 cm)
To find the concentration (c), rearrange the equation:
c = A / (ε * L)
Substituting the given values:
c = 0.427 / (6130 M^(-1) cm^(-1) * 1.00 cm)
c = 6.96 * 10^(-5) M
So, the concentration of compound M in the 5 mL volumetric flask is 6.96 * 10^(-5) M.
To calculate the percent purity of the compound, we need to know the molecular weight of the compound M, which is given as 292.16 g/mol.
First, find the number of moles of compound M in the 1 mL aliquot:
moles = concentration * volume
moles = 6.96 * 10^(-5) M * 1.00 mL * (1 L / 1000 mL)
moles = 6.96 * 10^(-8) mol
Next, find the mass of compound M in the 1 mL aliquot:
mass = moles * molecular weight
mass = 6.96 * 10^(-8) mol * 292.16 g/mol
mass = 2.03 * 10^(-5) g
To find the percent purity, divide the mass of compound M by the total mass of the sample and multiply by 100:
percent purity = (mass of compound M / mass of sample) * 100
percent purity = (2.03 * 10^(-5) g / 1.25 mg) * 100
percent purity = 1.624%
So, the percent purity of the compound is approximately 1.624%.
To find the concentration of compound M in the 5 mL volumetric flask, we'll use the formula:
Concentration (M) = Absorbance / (Molar absorptivity (M^-1 cm^-1) * Path length (cm))
(a) Calculate the concentration of compound M in the 5 mL volumetric flask:
First, let's calculate the absorbance of the 1 mL aliquot in the 10 mL volumetric flask:
Absorbance = 0.427
Next, we'll calculate the concentration of compound M in the 1 mL aliquot:
Concentration (M) = Absorbance / (Molar absorptivity * Path length)
Concentration (M) = 0.427 / (6130 M^-1 cm^-1 * 1 cm)
Concentration (M) = 6.9613 * 10^-5 M
Since the 1 mL aliquot was diluted to 10 mL, the concentration in the original 5 mL volumetric flask will be 10 times higher:
Concentration (M) in 5 mL flask = 6.9613 * 10^-5 M * 10 = 0.00069613 M
Therefore, the concentration of compound M in the 5 mL volumetric flask is 0.00069613 M.
(b) To calculate the percent purity of the compound, we need to know the molecular weight of the compound. However, the molecular weight is not provided in the question. Please provide the molecular weight of compound M in order to proceed with the calculation of percent purity.