Question

In: Chemistry

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams...

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for cadmium (Cd2 ) content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95° C overnight and ground them in a scientific blender, resulting in ~ 50 g of homogenized dry weight. A representative 64.00 mg sample was taken from the ~ 50 g of dry material and dissolved in 100.00 mL of 0.1 M HCl to create a sample solution. Using the method of standard additions, the chemist prepared five standard solutions in 100.00-mL volumetric flasks, each containing 5.00-mL aliquots of the sample solution. Varying amounts of a 89.0 ppb (μg ·L-1) cadmium standard were added to each of the flasks, which were then brought to volume with 0.1 M HCl. The solutions were then examined for their Cd2 content using GFAAS, resulting in the following absorbance data.

Determine the amount of Cd2 per gram of dry clam. Express your final result as milligrams of Cd2 per gram of dry clam

Sample cd2+ absorbance
5 2.50 0.119
5 5 0.163
5 7.50 0.200
5 10 0.241

Solutions

Expert Solution

Let us first calculate concentration of standard Cd2+ in the final diluted solutions

Cd2+ standard molar concentration = 89 ug/L = 0.089 mg/L

Absorbance due to sample with only 5 ml sample diluted to 100 ml (Ax) = 0.080

Sample                        Std. Cd2+ (mg/L)                                                Absorbance

1                  0.089 mg/L x 2.5 ml/100 ml = 2.225 x 10^-3 mg/L                    0.119

2                  0.089 mg/L x 5.0 ml/100 ml = 4.450 x 10^-3 mg/L                    0.119

3                  0.089 mg/L x 7.5 ml/100 ml = 6.675 x 10^-3 mg/L                    0.119

4                  0.089 mg/L x 10.0 ml/100 ml = 8.90 x 10^-3 mg/L                   0.119

Let concentration of Cd2+ in unknown clam in solution be Cx

concentration of std. Cd2+ in solution be Cs

Absorbance due to sample + std = A

Absorbance due to sample only without std = Cx

then,

Cx/(Cx + Cs) = Ax/A

taking first sample data

Cx/(Cx + 0.002225) = 0.08/0.119

0.119Cx - 0.08Cx = 1.78 x 10^-4

Cx = 4.56 x 10^-4 mg in 5 ml

Concentration of Cd2+ in 100 ml (64 mg Clam) solution = 4.56 x 10^-4 x 100/5 = 9.12 x 10^-3 mg

concentration of 50 g Clam sample = 9.12 x 10^-3 mg x 50 g/0.064 g = 7.125 mg

So mg of Cd2+/g of clam = 7.125 mg/50 g clam = 0.1425 mg/g clam


Related Solutions

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Cd2 content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95° C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 69.58 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for cadmium (Cd2 ) content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95° C overnight and ground them in a scientific blender, resulting in ~ 50 g of homogenized dry weight. A representative 91.65 mg sample was taken from the ~ 50 g of dry material and dissolved in...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for cadmium (Cd2 ) content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95° C overnight and ground them in a scientific blender, resulting in ~ 50 g of homogenized dry weight. A representative 91.65 mg sample was taken from the ~ 50 g of dry material and dissolved in...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Cd2 content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95° C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 73.11 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams...
An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for cadmium (Cd2 ) content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95° C overnight and ground them in a scientific blender, resulting in ~ 50 g of homogenized dry weight. A representative 64.00 mg sample was taken from the ~ 50 g of dry material and dissolved in...
A method used by the Environmental Protection Agency (EPA) for determining the concentration of ozone in...
A method used by the Environmental Protection Agency (EPA) for determining the concentration of ozone in air is to pass the air sample through a "bubbler" containing sodium iodide, which removes the ozone according to the following equation: O3(g)+2NaI(aq)+H2O(l)→O2(g)+I2(s)+2NaOH(aq) Part A) How many moles of sodium iodide are needed to remove 5.95×10−6 mol O3? Part B) How many grams of sodium iodide are needed to remove 2.1 mg of O3?
The Environmental Protection Agency (EPA) wants to investigate the value workers place on being able to...
The Environmental Protection Agency (EPA) wants to investigate the value workers place on being able to work in “clean” mines over “dirty” mines.  The EPA conducts a study and finds the average annual wage in clean mines to be $42,250 and the average annual salary in dirty mines to be $47,250.  If the probability of fatal lung disease after 10 years of work in a dirty mine is 3%, and is 1% in the clean mine, what is the statistical value of...
Problem 2 – The Environmental Protection Agency (EPA) is concerned about pollution caused by factories that...
Problem 2 – The Environmental Protection Agency (EPA) is concerned about pollution caused by factories that burn sulfur-rich fuel. In order to decrease the impact on the environment, factory chimneys must be high enough to allow pollutants to dissipate over a larger area. Assume that the mean height of chimneys in these factories is 100 meters (an EPA acceptable height) with standard deviation 12 meters. Use the appropriate Excel function to calculate each of the following. (Note – Part (b)...
Please critique the following experimental design: An ecologist with the Environmental Protection Agency (EPA) wants to...
Please critique the following experimental design: An ecologist with the Environmental Protection Agency (EPA) wants to investigate the effects of acid rain on the reproductive output of mustard plants. The scientist grows 1 mustard seed in mildly acidic water (pH = 6) and 1 mustard seed in neutral water (pH = 7). The temperature and photoperiod was kept the same between both treatment and control. All plants were given 40 days to develop to seed.
In September 2015, the United States Environmental Protection Agency (EPA) disclosed a notice of violation of...
In September 2015, the United States Environmental Protection Agency (EPA) disclosed a notice of violation of the Clean Air Act to German automaker Volkswagen Group. The agency reported that Volkswagen had intentionally programmed turbocharged direct injection (TDI) diesel engines to activate their emissions controls only during laboratory emissions testing which caused the vehicles' nitrogen oxide (NOx) output to meet US standards during regulatory testing, but emit up to 40 times more NOx in real-world driving. Volkswagen deployed this programming software...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT