-- Posted by morgan82 at 5:27 pm on Jan. 5, 2009 I have 250 grams of Al2(PO4)3 How many moles of Al are there? -- Posted by Amazingness99 at 5:28 pm on Jan. 5, 2009 Calculate the molar mass of Al2(PO4)3 first. Then, divide 250 by the number you got and you should get the moles of that substance. -- Posted by Heart92 at 5:29 pm on Jan. 5, 2009 Do you have more questions? I can help you out with the others. -- Posted by mynoselikesopiates at 5:32 pm on Jan. 5, 2009 cook up some meth -- Posted by Just Waiting Here at 5:38 pm on Jan. 5, 2009 You need to calculate the molar mass.  You do this by using the weights that you get off of a periodic table. You have Al2(PO4)3, which means you have 2 aluminum, 3 phosphorus, and 12 oxygen. Add up all the weights together to get your molar mass of this compound. Since you have 250 grams, and molar mass is in grams per mole, you need to divide 250 by the number you just calculated.  This will give you the number of moles.