A slow oxidation reaction in aqueous solution generates a faint orange product that…
CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A slow oxidation reaction in aqueous solution generates a faint orange product that strongly overlaps with the absorbance of dissolved O2. The lab has the following equipment:
• Digital manometer attached to the sealed reaction flask
• UV–visible spectrophotometer (400–800 nm)
• Dissolved-oxygen probe that requires recalibration every 30 s
The reaction is expected to proceed for several hours and produces negligible gas volume. Which monitoring approach would most likely provide accurate rate data for the appearance of the orange product?
(a) Continuously record changes in total pressure with the manometer to relate them to product formation
(b) Monitor absorbance at 450 nm without first confirming that dissolved O2 does not absorb at that wavelength
(c) Periodically withdraw tiny aliquots and measure absorbance at a wavelength where only the orange product absorbs
(d) Place the dissolved-oxygen probe directly in the flask even though it must be recalibrated every 30 s