Question

Spectrophotometer measures the transmittance or the absorbance, or both, of a particular wavelength or light after it has passed through a liquid sample. The liquid sample holder is commonly known as a cuvette. Before the transmittance or absorbance of the sample is measured, a cuvette filled only with solvent, called the blank, is placed in the spectrophotometer. Select the statement from the following that is true for why is a blank measured before the sample.

A. A blank is measured to remove the signal caused by the cuvette walls and solvent.
B. A blank is measured to calibrate the spectrophotometer's light source.
C. There is no reason to measure a blank before the sample.
D. A blank is measured to clean the spectrophotometer.

Answer 1

The correct answer is A. A blank is measured to remove the signal caused by the cuvette walls and solvent.

Step-by-step explanation:

In Spectophotometry, the blank is the solvent or the medium in which its is dispersed the target molecule to measure. The solvent/medium could absorbe the incident light at the measurement wavelenght, so it must be corrected ir order to obtain the specific absorbance of the sample. Absorbance of the blank is removed (setted to 0 absorbance) and after that, the cuvette with sample is placed and measured.