A dye solution of concentration is placed in two different rectangular cuvettes made…

CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures

Problem

A dye solution of concentration

4.50 \times 10^{-5}\,\text{M}

is placed in two different rectangular cuvettes made of the same optical material. One cuvette has a path length of

1.00\,\text{cm}

, and the other has a path length of

5.00\,\text{cm}

. The spectrophotometer is calibrated so that all other variables remain constant. When the

1.00\,\text{cm}

cell is used, the measured absorbance is

0.120

. (a) Calculate the absorbance that should be observed when the

5.00\,\text{cm}

cell is used with the same dye solution. (b) A student actually measures an absorbance of

0.575

with the

5.00\,\text{cm}

cell. Determine the percent deviation of the student’s value from the absorbance calculated in part (a). (c) The instrument can reliably detect absorbance values as low as

0.050

. If solutions of this dye as dilute as

1.00 \times 10^{-5}\,\text{M}

must be quantified, which cuvette (

1.00\,\text{cm}

5.00\,\text{cm}

) should be selected? Support your answer with a calculation. (d) Discuss one experimental drawback that might arise from routinely using the longer path-length cuvette for highly concentrated samples of the dye.

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