Use the spaces provided for the answers and additional paper if necessary. Accor

Question

Use the spaces provided for the answers and additional paper if necessary. According to the Handbook of Chemistry and Physics: KAl(SO_4)_2 12 H_2O is very soluble in hot water: 11.4 g of KAl(SO_4)_2 12 H_2O will dissolve in 100 mL of cold water, and Kal(SO_4)_2 12 H_2O is insoluble in ethanol. (a) Briefly explain why you rinsed the alum crystals with cooled 95% ethanol, rather than distilled water, in Step 17. (b) How would your percent yield have been affected if you had not cooled the reaction mixture before filtering it to isolate the crystals? Briefly explain. Two students were late reporting to the laboratory, and they were both rushing to complete the experiment outlined in the Procedure. In their haste, they each spilled a small amount of filtrate, one after completing Step 7, the other after completing Step 17. Which student's results would more likely be affected by the error? Briefly explain. A student began the Procedure with 0.485 g of aluminum foil. She subsequently calculated a percent yield of 28.7% for her experiment. Determine the mass of alum she produced.

Explanation / Answer

Q1.

a)

This is correct, we rinse this in order to increase and clean

b)

% yield affected if:

we do not cool the reaction mix --> the solubility will be HIGHER, therefore, material is still in aqueous solution, will not be solid, which implies we cant recover it with filtration.

If it is not recovered, then expect LESS amount of material, therefore, the yield DECREASES

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