Question

a simultaneous determination for cobalt and nickel can be based on absorption by their respective 8-hydroxyquinolinol complexes. molar absorptivities corresponding to their absorption maxima are as follows: molar absorptivity, e 365 nm co 3529 ni 3228 700 nm 428.9 10.2

Answer 1

The molar absorptivities for cobalt and nickel can be used to determine their concentration based on absorbance measurements at specific wavelengths.

Step-by-step explanation:

A simultaneous determination for cobalt and nickel can be based on absorption by their respective 8-hydroxyquinoline complexes. The molar absorptivities for cobalt and nickel at their absorption maxima are 3529 L*mol-1*cm-1 and 3228 L*mol-1*cm-1, respectively, at 365 nm. At 700 nm, the molar absorptivities for cobalt and nickel are 428.9 L*mol-1*cm-1 and 10.2 L*mol-1*cm-1 respectively. The molar absorptivities are characteristic values for a given compound and can be used to calculate the concentration of the sample based on the absorbance measured at a specific wavelength.

Answer 2

The question involves the use of absorption spectroscopy to determine the concentration of cobalt and nickel by their molar absorptivity values, which are characteristic for each complex at specific wavelengths and are used in Beer's Law calculations.

Step-by-step explanation:

Absorption Spectroscopy and Molar Absorptivities

The question refers to a simultaneous determination of cobalt and nickel based on their absorption of light when they form complexes with 8-hydroxyquinolinol. The molar absorptivity (also known as the extinction coefficient) is a measure of how strongly a chemical species absorbs light at a given wavelength and is represented by the Greek letter epsilon (ɛ). When provided with the molar absorptivity and absorbance of a solution at its absorption maximum, we can calculate the concentration using Beer's Law: A = ɛcl, where A is the absorbance, ɛ is the molar absorptivity, c is the concentration, and l is the path length, which is usually 1 cm.

In the context of coordination complexes and their colors, the specific ligands coordinated to the metal center greatly influence their color. This occurs because different ligands affect the energy levels of the d-orbitals and thus change the wavelength (color) of light absorbed. For example, a complex with a high-spin configuration might absorb photons in a different part of the spectrum than a low-spin configuration of the same metal ion, leading to different observed colors.

It's important also to note that the spectral properties of biochemically relevant molecules, like NAD+ and aromatic amino acids, are frequently used in spectroscopic analysis to determine concentration and to understand more about their structure and function.