Beer's Law and Spectrophotometry

The molar absorptivity of a compound at 500 nm wavelength is 252 M-1cm-1. Suppose one prepares a solution by dissolving 0.00140 moles of a solute in enough water to make a 500.0 mL solution. What would be the absorbance in a 5 .00 mm pathlength cell?

0.353

A measurement of the amount of light taken in by a sample

Absorbance

What type of plot can be used to determine λmax of a solution?

Absorbance vs. wavelength

red line

Consider the given plot of absorbance vs. concentration. Which line is the best-fit line to represent the black data points?

A square-shaped container, typically made of quartz, designed to hold samples in a spectrophotometer

Cuvette

What should be done if a spectrophotometer reports an absorbance that is too high?

Dilute the sample

1.8E-5

Examine the given Beer's law standard curve for an unknown dye measured in a 1.0 cm cuvette. What is the concentration (in M) of a sample of the unknown dye with an absorbance of 0.25 at 542 nm?

Identify the color absorbed by a solution that appears the color given. Green- Orange- Red- Blue-

Green- Red Orange- Blue Red- Green Blue- Orange

Title y-axis numeric range x-axis label

Identify the aspects of the pictured graph that are missing or contain errors.

Suppose you prepare a 5μm solution of red dye and a 5μm solution of blue dye and observe them in two identical test tubes. Why might the blue dye solution appear more intensely colored than the red dye solution?

The molar absorptivity of the blue dye is greater than the molar absorptivity of the red dye

A measurement of the amount of light that passes through a sample

Transmittance

Identify the first step in preparing a spectrophotometer for use.

Turn on the light source and the spectrophotometer.

A sample prepared using the solvent and any other chemicals in the sample solutions, but not the absorbing substance

blank

To run a spectrophotometry experiment, begin by _________________the spectrophotometer and preparing the samples. Be sure to select the __________, then run a measurement on the ____________solution. Follow up by running measurements on _____________solutions. Once data is collected, turn off the instrument, clean the area, and discard the samples.

warming up wavelength blank sample

A unit commonly used in spectrophotometry that is inversely proportional to energy and commonly measured in nanometers

wavelength

To prepare a standard (calibration) curve for a spectroscopy experiment, start by preparing ___________ with _____________ unknown concentrations. Then, measure the ____________of each solution at ____________ and create a plot of _________for the measured values. Finally, find the best-fit line of the data set.

multiple solutions different known concentrations absorbance the same wavelength absorbance v concentration