Question

in step 9 of the synthesis, why is the beaker of solution placed in an ice bath? select one: to freeze the solution solid so the alum can be scraped out. to speed up the reaction between the ions. to greatly decrease the solubility of alum in water, causing it to crystallize out of the solution. to prevent the beaker from getting too hot and breaking.

Explanation:

• Freezing the solution solid is not the goal as alum crystallization is about solubility change, not freezing.
• Lowering temperature (ice bath) slows down reactions, so it doesn't speed up ion - ion reactions.
• Alum's solubility in water decreases with lower temperature. Placing in an ice bath lowers the temperature, making alum less soluble and thus crystallize out.
• The main purpose is related to alum's properties (solubility) rather than protecting the beaker from heat (since we are cooling, not heating).

Answer:

To greatly decrease the solubility of alum in water, causing it to crystallize out of the solution.