How is the concentration of a chemical substance determined using a spectrophotometer?

The correct answer is based on the fundamental principle of how a spectrophotometer works. A spectrophotometer measures the amount of light that passes through a sample at a specific wavelength. When a beam of light passes through a solution containing a chemical substance, the substance will absorb some of the light, depending on its concentration. The extent of light absorption is quantified as "light intensity," often represented by absorbance.

The concentration of the substance can be determined using Beer-Lambert Law, which states that absorbance is directly related to the concentration of the substance in the solution. By comparing the intensity of the light before and after it passes through the solution, the spectrophotometer provides a measurement that correlates directly to the concentration of the chemical in the sample.

In this context, other methods such as measuring temperature, color changes, or pH do not provide a direct and quantitative means to determine chemical concentration as effectively as light intensity measurement does. Measurement of temperature or pH might influence the chemical reactions or state of substances but does not give a specific indication of concentration. While color changes may indicate a reaction or concentration in a qualitative way, it lacks the precision and quantifiability provided by direct light intensity measurement in a spectroph