7. Is it better to wash a filtered solid with one large portion of cold water or

Question

7. Is it better to wash a filtered solid with one large portion of cold water or a few small portions? Would you get a more accurate mass by: 1) taring filter paper, filtering, drying, and obtaining a mass, or 2) filtering, drying, then scraping the solid onto a tared watch glass to obtain the mass'? 9. What could you do to make the ratio of carboxylic acid to carboxylic acid salt closer to equal at equilibrium? You can think conceptually or mathematically,remember at pH 2: [H [C.H.COOH = 155 K, [CH COO

Explanation / Answer

7. Answer: A few small portions.

A few small portions (as little as possible) prevent product loss.

8. Answer: Filtration, the technique used to separate solids from liquids, is the act of pouring a mixture onto a membrane (filter paper) that allows the passage of liquid (the filtrate) and results in the collection of the solid.

case 2 when filtering,drying,then scraping the solid onto a tared watch glass to obtain the mass.

This offers the least chance for major error. By filtering the solid, drying, and scraping onto a watch glass we not only get a mass of what can actually be carried on to the next reaction step but you will likely lose <20 milligrams if we carefully scrape the filter paper.This requires careful scraping to avoid scraping away the filter paper material itself.

case 1 assumes the filter paper is a constant mass throughout the process.However, if we are filtering a solution containing NaCl then there will likely be an unknown amount of salt absorbed into the filter paper which could leads to false high masses (potentially hundreds of milligrams high).

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