Solving Moles of Potassium Alum: Water Included?

[lexia925]

when determining moles of potassium alum, do you need to count the 12 moles of water also? and how would you do that--just 2 x 12? or something else? soooo confused.

 

[Cesium]

If the problem deals with KAl(SO₄)₂·12(H₂O), then you must take into the account the moles of water when calculating the molar mass. Then your answer will be correct when finding the number of moles. You must add 12 x the molar mass of water to your molar mass.