### Glass Contamination Problem?

Glass is a notorious source of metal ion contamination. Three glass bottles were crushed and sieved to collect 1 mm pieces. To see how much Al3+ could be extracted, 240. mL of a 0.05 M solution of the metal-binding compound EDTA was stirred with 0.50 g of the 1 mm glass particles in a polyethylene flask. The Al content of the solution after 2 months was 5.2 ÃŽÂ¼M. The total Al content of the glass, measured after completely dissolving some glass in 48 wt% HF with microwave heating, was 0.80 wt%. What fraction of the Al was extracted from the glass by EDTA? (Enter your answer to 5 decimal places.)

StraightToThePoint

on November 30th, -0001

There are only two pieces of useful information in this long story problem, the amount of aluminum extracted and the percentage of aluminum in the original sample.

The amount extracted is given in ‘micromoles’. A mole of aluminum is the molecular weight from the periodic table, and a micromole is 1 millionth of a mole. Aluminum is approximately 27 grams per mole, so 1 micromole would be 2.7E-5 grams and 5.2 uM would be 1.4E-4 grams.

The amount originally present is given as a weight percentage. The sample which was extracted was 0.5 gms and it contained 0.8% aluminum. Expressed as a fraction, the percentage is 0.008, and 0.004 grams would be present in a 0.5 gram sample.

The percent yield would be the amount extracted divided by the amount originally present. This is 0.00014 grams divided by 0.004 grams, or 0.035 or a 3.5 percent extraction.

If the answer has to be 5 significant places, try to rework the problem using a more accurate molecular weight and proceed from there. The number of bottles, the concentration and volume of the EDTA solution and the particle size of the crushed glass have nothing to do with calculating the answer, and is all useless information.