The absorbance of a chlorophyll a standard solution in ethanol (density = 0.785 g/mL) is measured in
a 1.3 cm cuvette or path length. The absorbance is 0.435 and the molar absorptivity coefficient is 86,300 M–1cm–1.
The molecular weight for chlorophyll a is 893.49 g/mol.
The absorbance of a chlorophyll a standard solution in ethanol (density = 0.785 g/mL) is measured in
a 1.3 cm cuvette or path length. The absorbance is 0.435 and the molar absorptivity coefficient is 86,300 M–1cm–1.
The molecular weight for chlorophyll a is 893.49 g/mol.
A) What is the molar concentration of the solution? (I've already gotten.)
B) What is the concentration of the solution in ppm?
What did you get for M? If I call that 4E-6M (an estimate on my part) then that is
4E-6 mols/L EtOH or 4E-6 mols/785g (since density is 0.785g/mL then 1000 mL will have a mass of 785 g).
4E-6 mols x molar mass = grams chlorophyll = about 0.004 g chlorophyll. That is in 785g soln or 0.004/785 = about 5E-6 g/g. That makes it 5E-6*(10^6/10^6) = about 5 ppm.
That makes chlorophyll 4E-6/785 =
The molar concentration is 3.87E-6.
thank you!
i still don't get it
molar concentration of solution: 3.87 x 10^-6
concentrationin ppm: 4.4
To calculate the concentration of the solution in ppm (parts per million), you need to convert the molar concentration to ppm.
A ppm is a unit of concentration that represents the ratio of the mass of the solute to the mass of the solution, multiplied by one million.
Here's how you can calculate the concentration in ppm:
1. Calculate the mass of the solute (chlorophyll a) in grams.
Mass of chlorophyll a = molar concentration (mol/L) * volume of solution (L) * molecular weight (g/mol)
2. Calculate the mass of the solution in grams.
Mass of solution = volume of solution (L) * density of ethanol (g/mL) * 1000 (to convert mL to grams)
3. Calculate the ppm concentration.
ppm concentration = (mass of solute / mass of solution) * 1,000,000
Let's plug in the given values and calculate the concentration in ppm:
Given:
- Molar concentration = 0.435 M (already calculated in part A)
- Volume of solution (cuvette) = 1.3 cm = 0.0013 L (since 1 cm^3 = 0.001 L)
- Molecular weight of chlorophyll a = 893.49 g/mol
- Density of ethanol = 0.785 g/mL
Step 1: Calculate the mass of chlorophyll a
mass of chlorophyll a = 0.435 M * 0.0013 L * 893.49 g/mol = 0.501 g
Step 2: Calculate the mass of the solution
mass of solution = 0.0013 L * 0.785 g/mL * 1000 = 1.022 g
Step 3: Calculate the ppm concentration
ppm concentration = (0.501 g / 1.022 g) * 1,000,000 = 490,163 ppm
Therefore, the concentration of the solution in ppm is approximately 490,163 ppm.