Question

In: Chemistry

Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36400 and...

Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36400 and εNi = 5520 at 510 nm and εCo = 1240 and ε Ni = 17500 at 656 nm. A 0.322-g sample was dissolved and diluted to 250.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3-quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance of 0.650 at 510 nm and 0.588 at 656 nm in a 1.00-cm cell.
Calculate the concentration of cobalt (in ppm) in the initial solution prepared by dissolving the sample.

Solutions

Expert Solution

Absorbance of solution = Absorbance due to Co + absorbance due to Ni

Absorbance = molar absorptivity x concentration x path length

with path length = 1 cm

molar absorptivity at 510 nm,

For Co = 36400 M-1.cm-1

For Ni = 5520 M-1.cm-1

molar absorptivity at 656 nm,

For Co = 1240 M-1.cm-1

For Ni = 17500 M-1.cm-1

let [Co] and [Ni] represent the concentration of Co and Ni in diluted solution

then,

0.650 = 36400[Co] + 5520[Ni]  ...... at 510 nm

0.588 = 1240[Co] + 17500[Ni]  ...... at 656 nm

Solving the two equations,

[Co] = 1.3 x 10^-5 M

[Ni] = 3.3 x 10^-5 M

Concentration in 25 ml aliquot,

[Co] = 1.3 x 10^-5 M x 50 ml/25 ml = 2.6 x 10^-5 M

[Ni] = 3.3 x 10^-5 x 50 ml/25 ml = 6.6 x 10^-5 M

concentration (ppm) in original solution prepared by dissolving sample,

[Co] = 2.6 x 10^-5 M x 250 ml x 58.93 g/mol x 1000/25 ml = 15.322 ppm

[Ni] = 6.6 x 10^-5 M x 250 ml x 58.69 g/mol x 1000/25 ml = 38.735 ppm


Related Solutions

P23-27: Molar absorptivity data for the cobalt and nickel complexes with 2,3- quinoxalinedithiol are εCo =...
P23-27: Molar absorptivity data for the cobalt and nickel complexes with 2,3- quinoxalinedithiol are εCo = 36,400 and εNi = 5520 at 510 nm and εCo = 1240 and εNi = 17,500 at 656 nm. A 0.425-g sample was dissolved and diluted to 50.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance of 0.446 at 510 nm and 0.326 at 656 nm in...
The following information is to be used for the next two questions. Molar absorptivity data for...
The following information is to be used for the next two questions. Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36400 and εNi = 5520 at 510 nm and εCo = 1240 and ε Ni = 17500 at 656 nm. A 0.445-g sample was dissolved and diluted to 250.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3-quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance...
The following information is to be used for the next two questions. Molar absorptivity data for...
The following information is to be used for the next two questions. Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36400 and εNi = 5520 at 510 nm and εCo = 1240 and ε Ni = 17500 at 656 nm. A 0.583-g sample was dissolved and diluted to 200.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3-quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance...
The following information is to be used for the next two questions. Molar absorptivity data for...
The following information is to be used for the next two questions. Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36400 and εNi = 5520 at 510 nm and εCo = 1240 and ε Ni = 17500 at 656 nm. A 0.556-g sample was dissolved and diluted to 150.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3-quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance...
The following information is to be used for the next two questions. Molar absorptivity data for...
The following information is to be used for the next two questions. Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36400 and εNi = 5520 at 510 nm and εCo = 1240 and ε Ni = 17500 at 656 nm. A 0.514-g sample was dissolved and diluted to 150.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3-quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance...
A voltaic cell is composed of nickel metal in a nickel II solution and cobalt metal...
A voltaic cell is composed of nickel metal in a nickel II solution and cobalt metal in a cobalt II solution. Write a balanced net ionic equation for the reaction including states of matter.
Cobalt Ceramics, Inc., acquired a manufacturing facility (building) from Nickel Construction Company. Nickel completed construction of...
Cobalt Ceramics, Inc., acquired a manufacturing facility (building) from Nickel Construction Company. Nickel completed construction of the facility on January 1, 2021. In payment for the $6 million lighthouse, Cobalt issued a five-year installment note to be paid in five equal payments at the end of each year. The payments include interest at the rate of 5.4%. Instructions Prepare the journal entry for Cobalt’s purchase of the facility on January 1, 2021. Prepare the journal entry for the first installment...
There are 1.20g of Cobalt and 1.80g of oxygen. What is the molar ratio?
There are 1.20g of Cobalt and 1.80g of oxygen. What is the molar ratio?
1. a. Dye have very high molar absorptivity. Why is this an advantage for their use...
1. a. Dye have very high molar absorptivity. Why is this an advantage for their use in food products? b. How do we "blank the spectrophotometer"? Why is it done?
1) The equation A=Ebc directly relates the concentration of a sample, its molar absorptivity (E), and...
1) The equation A=Ebc directly relates the concentration of a sample, its molar absorptivity (E), and the absorbance of a sample. Instead of bothering with a standard curve, why not make two measurements: first, measure the absorbance of a sample of known concentration in order to compute the molar absorptivity. Second, measure the absorbance of the solution with unknown concentration and use the molar absorptivity from the first to calculate the concentration. Explain why this would, or would not, be...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT