Question

Hi. What mass of phosporus is present in 5.00 mols of the compound P406 ?

I need to use dimensional analysis, and I know that P406 has a mass of 219.88 grams, but I don't know how to get phosphorus by itself.

Thank you!

Answer 1

5.00 mols P4O10 x (4 mols P/1 mol P4O10) = mols P.

mols P x atomic mass P = g P.

I bring this up however. P is usually written P4. If you have encountered this, then what I have written above for mols P will give the same answer since 4P and P4 have the same mass. But the conversion to grams must be done differently; i.e., mols P4 x atomic mass P4 = grams P4. I can't tell which your prof is using from the question asked.