A laboratory technician uses a spectrophotometer set to the wavelength of maximum…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A laboratory technician uses a spectrophotometer set to the wavelength of maximum absorbance for the aqua cobalt(II) ion. A calibration standard that is known to be 0.0750 M in Co(NO₃)₂ is placed in a 1.00 cm path-length cuvette and gives an absorbance reading of 0.609.
Immediately afterward, an unknown cobalt(II) solution is measured in the same cuvette under identical instrumental settings and yields an absorbance of 0.482.
(a) Calculate the molar concentration of the unknown cobalt(II) solution. Report your answer to the correct number of significant figures and include units.
(b) Briefly describe one procedural reason, other than convenience, for using the *same* cuvette to measure both the standard and the unknown.