[VISUAL] A student uses a galvanic cell to determine the concentration of ethanol, C2H5OH, in an aqu — Electrochemistry Chemistry Question
Problem Context
[VISUAL]
A student uses a galvanic cell to determine the concentration of ethanol, C2H5OH, in an aqueous solution. The cell is based on the half-cell reactions represented in the table above.
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An alternative approach to determine the concentration of C2H5OH(aq) in a solution is based on the reaction represented below.
3 C2H5OH(aq) + 2 Cr2O7 2−(aq) + 16 H+(aq) → 4 Cr3+(aq) + 3 CH3COOH(aq) + 11 H2O(l)
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A solution has an initial Cr2O7 2−(aq) concentration of 1.0 × 10−3 M and an initial C2H5OH(aq) concentration of 0.500 M. The solution contains enough strong acid to keep the pH essentially constant throughout the reaction. The student places a sample of the solution in a cuvette that has a path length of 0.50 cm and places it in a spectrophotometer set to measure absorbance at 440 nm. (Cr2O7 2−(aq) is the only species in the reaction mixture that absorbs light at this wavelength.) The absorbance of Cr2O7 2−(aq) in the solution is monitored as the reaction proceeds; the table below shows the absorbance as a function of time for the first trial.
[VISUAL]