Question

question 7 of 10
points possible: 1.00
not yet answered
in the final step of the synthesis (step 10), why are the collected crystals washed with an aqueous ethanol solution instead of pure distilled water?
select one:
pure water is not effective at washing away the sulfuric acid.
the ethanol reacts with any remaining impurities to neutralize them.
alum is less soluble in the ethanol solution than in pure water, which minimizes the amount of product that dissolves and gets lost during washing.
the ethanol helps to dry the crystals more quickly.

Explanation:

Alum (a salt) has lower solubility in ethanol - water mixture. Using this mixture reduces alum dissolution during washing, minimizing product loss. Ethanol also aids faster drying. Pure water would dissolve more alum (higher solubility), and ethanol doesn't react with impurities to neutralize them.

Answer:

Alum is less soluble in the ethanol solution than in pure water, which minimizes the amount of product that dissolves and gets lost during washing.