A polarogram of reagent-grade methanol is shown in trace a. Trace b shows reagen

Question

A polarogram of reagent-grade methanol is shown in trace a. Trace b shows reagent methanol with added 0.001 00 wt% acetone. 0.001 00 wt% acetaldehyde, and 0.001 00 wt% formaldehyde. Scales are the same in both panels. Solutions were prepared by diluting 25 mL of methanol up to 100 mL with water containing buffer and hydrazine sulfate, which reacts with carbonyl compounds to form electroactive hydrazones. An example is shown below: From the two polarograms, estimate the wt% of acetone in reagent-grade methanol. Polarograms of reagent grade methanol and methanol containing added standards. [D.B. Palladino, Am. Lab, August 1992, P. 56].

Explanation / Answer

Given,

Solution,

The relative heights of the signals for acetone are given as ,

Signal for unknown / (signal for unknown + standard) = 0.259

Xi / (Sf + Xi) = Ix / IS+X

So, { x (wt %) / (0.00100 + x) } = 0.259

So, x = 0.00035 wt %

So, weight percent of acetone in reagent grade methanol is 0.00035.

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