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Moderate

Alum Lab Data

APCHEM-7EXLND

The “alum” used in cooking is potassium aluminum sulfate hydrate, $KAl(SO_4)_2• x H_2O$ . To find the value of $x$, a sample of the compound is heated. The mass of the empty crucible is 20.01 g.

The alum hydrate was added to the crucible until the total mass of the crucible and hydrate was 24.75 g. The sample was heated in the crucible until the final mass of the crucible and anhydrous product was 22.59 g.

Which of the following is the value of $x$?

A

2

B

3

C

12

D

18