Michael L. answered • 05/27/22
25 years experience teaching Chemistry (including AP)
We have to find out the mass one *one* mole of Sr(C2H3O2)2 and divide by that. (Just like if someone said they had 24 pounds of cookies and asked how many cookies that was, we'd find out the weight of one cookie and divide by that.) We get the mass of one mole by looking up Sr, C, H and O in the periodic table. Sr shows as 87.62 grams per mole, C=12.01, O=16 and H=1.008. Multiplying by the number of each and adding them all up we get 1*87.62 + 4*12.01 + 6*1.008 + 4*16 = 205.708. So 166.2 grams would be 166.2 / 205.708 = .8079 moles. Reality check: 166.2 is smaller than 205.708 so it makes sense that we didn't even get one whole mole.
