Spectrometry book questions Flashcards
18-6, How does transmittance, absorbance and molar absorbitivy differ? Which one is proprtotional to concentration?
Absorbance (A), also known as optical density (OD), is the quantity of light absorbed by a solution. Transmittance is the quantity of light that passes through a solution.
It is a unique physical constant of the chemistry of the sample that relates to the sample’s ability to absorb light at a given wavelength.
According to the Beer-Lambert law, the absorbance of a solution is directly proportional to the concentration of the absorbing material present in the solution and path length.
7,What is an absorbtion spectrum?
It’s a graph of adsbotion vs wave lenght
10,Why is it most accurate to measure absorbance in range A=0.3-2
Because if adsbotion is too high too little light reaches the detector and if adsobtion is too low there is little difference between the sample and the reference for accurate measurmeant
16 a, What would the callibration curve look like if the reagent blank absorbance of 0.038 were not substracted from absorbance readings?
The curve would have the same slope but would have a positive intercept equal to the absorbance of the reagent blank.
16 b, What would the blank corrected callibration curve look like if absorbance was measured at 600 instead of 562? Why is it poo practise to measure absorbance on the steep side rather of a peak rather then the peak wave lenght?
Molar absborivity is lower at 600nm then 562nm so the slope of the cellibration curve would be lower.
32, what is the difference between flourescense and phosphorescense?
Flourescense is the emission of light without change of the electronic spin state. With phosrphorescense the electronic spin state changes. Phosprohrescense the molecules spend more time in an excited state which means it has a longer life time then flourescense and it comes at a lower energy (longer wave lenght) then flourescense.
35, What is the difference between flourescense excitation spectrum and flourescense emission spectrum? Which spectrum resembles an adsobtion spectrum?
In excitation spectrum the eciting wave lenght is varier wghile the detector wave lenght is fixed. In emission spectrum the exciting wave lenght is fixedand the detector wave lenght is varied.
