In order to determine the amount of moles in 23g of phosphorus, you must use math.
To get the answer, you must multiply the molar mass of phosphorus, which there is 30.97g in 1 mol, and put the mol over the mass, then multiply by your desired amount you want, which is 23g; it would look like this:
(23.00g)( 1 mol = x
30.97g )
Then you plug the answers into a calculator and you should get the answer of 0.74265.
