What does \"OD\" mean in the following chemistry problem answer? Question: If yo

Question

What does "OD" mean in the following chemistry problem answer?

Question: If your curvette had been dirty, how would this have affected the value of ksp?

Answer: the more dirt on the cuvette when you take a reading, the higher the OD. this is because OD determines how much light can pass through a sample. the light that passes through the cuvette hits particles in the sample and cannot get through. therefore, the more concentrated a solution, the higher the OD will be. if you have a very dilute concentration of ions and you put this in a dirty cuvette, the OD reading will be applicable to a high concentration of those ions. the fact that light cannot pass through a dirty cuvette will alter the Ksp in that the reading will tell you that you have more soluble product than there actually is.

Explanation / Answer

Transmittance (T) is defined as the fraction of incident light which is transmitted, ie, passes through, a sample. Thus, T = I/Io, where Io equals the intensity of light which strikes the sample and I is the intensity of light after passing through the sample. Transmittance is usually expressed as a percentage:

%T = (I/Io) x 100

Absorbance (A), or optical density, is a logarithmic function of T and is expressed as:

A = log10 (1/T) = log10 (Io/I)

Note that absorbance has no units. The shorthand for absorbance is Axxx, where xxx is the wavelength at which made the measurment.

So, for example, at 100% transmittance, A = log 1.0 = 0. At 50% transmittance, A = log (1/0.5) = 0.30. Your Spec 20 has two scales, one calibrated from 0 to 100% Transmittance and the other as Absorbance, ranging from infinity to 0. Note that the highest calibrated unit of absorbance is 2.0. Spectral data are usually plotted as absorbance (Y-axis) vs wavelength or concentration (X-axis)

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