d. You want to determine the amount of Chlorophyll (Molecular Weight: 893.51 g/mol) in a 50 ml marine sample. Before analysis by UV spectroscopy, 5 ml of the solution was diluted to 80 ml with DI water. The diluted sample was analysed using UV spectroscopy and had an absorbance of 0.320 at 670 nm. What was the amount in mg of Chlorophyll in the original sample?
50ml
To determine the amount of Chlorophyll in the original sample, we need to calculate the concentration of Chlorophyll in the diluted sample, and then convert it to the concentration in the original sample.
Step 1: Calculate the concentration of Chlorophyll in the diluted sample.
To calculate the concentration, we can use the Beer-Lambert Law, which relates the absorbance of a sample to its concentration.
The Beer-Lambert Law is given by:
A = εcl
Where:
A = Absorbance
ε = Molar absorptivity (path length dependent constant)
c = Concentration
l = Path length
In our case, the absorbance (A) is 0.320, and the path length (l) is 1 cm. We need to find the concentration (c).
We can rearrange the Beer-Lambert Law equation to solve for concentration (c):
c = A / (ε * l)
However, we need the molar absorptivity (ε) value for Chlorophyll at 670 nm to proceed.
Step 2: Find the molar absorptivity (ε) value for Chlorophyll at 670 nm.
Unfortunately, the molar absorptivity value is not provided in the question. To proceed, we need to look up the molar absorptivity value for Chlorophyll at 670 nm. This information can be found in a reference book or scientific database.
Once we have the molar absorptivity value, we can substitute it into the equation calculated in Step 1 to find the concentration (c) of Chlorophyll in the diluted sample.
Step 3: Calculate the concentration of Chlorophyll in the diluted sample.
Using the calculated concentration (c) from Step 2, we can substitute it into the equation:
c = A / (ε * l).
Step 4: Calculate the amount of Chlorophyll in the original sample.
Now that we have the concentration of Chlorophyll in the diluted sample, we can calculate the amount of Chlorophyll in the original sample.
To do this, we first need to calculate the volume (V) of the original sample. The diluted sample was obtained by diluting 5 ml of the original sample to 80 ml.
To calculate V, we can use the following equation:
V * (concentration of original sample) = (volume of diluted sample) * (concentration of diluted sample)
Rearranging the equation to find V:
V = [(volume of diluted sample) * (concentration of diluted sample)] / (concentration of original sample)
Once we have V, we can calculate the amount of Chlorophyll in the original sample using the following equation:
Amount of Chlorophyll in original sample = (concentration of Chlorophyll in diluted sample) * V
Finally, we can convert the amount to mg by multiplying it by the molecular weight of Chlorophyll (893.51 g/mol) and converting grams to milligrams.
Please note that you will need to provide the molar absorptivity value for Chlorophyll at 670 nm in order to complete the calculations.