If there are 65.2 grams of Na3PO4 , how many moles are there? PLEASE SHOW WORK

Answer 1

Hey Zabdi,

So first we have to figure out the conversion factor of grams of Na3PO4 to moles of Na3PO4. This is just the molecular weight of Na3PO4. We do this by looking at the periodic table, which gives the molecular weight of every single element. The molecular weight tells you how many grams of that element makes up one mole of that element.

Molecular weight of Na: 22.99 g/mol

Molecular weight of P: 30.97 g/mol

Molecular weight of O: 15.99 g/mol

In Na3PO4, there are 3 Na, 1 P, and 4 O. So the total molecular weight is 3(22.99) + 1(30.97) + 4(15.99) = 163.9 g/mol. So this is your conversion factor.

Now you multiply your 65.2 g by the conversion factor, making sure that the "g"s are canceled out. This method is known as dimensional analysis:

65.2 g x (1 mol/163.9 g) = 0.398 moles of Na3PO4.

Note: It is very important that you invert the conversion factor, otherwise when you multiply, you'll get units of g^2/mol (which doesn't make any sense), instead of mol.