Platinum `(Pt)` is a hard silvery-white metal. How many moles of `Pt` atoms are in `292.64 g` of `Pt` metal?
Strategy: Elementary entiteis of `Pt` metal are atoms. The atomic mass of `Pt` is `195.09 u` thus, the molar mass of `Pt` is `195.09 "g mol"^(-1)`.

Explanation

Unitary method
`195.09 gPt = 1 mot Pt` atoms
`1g Pt = (1)/(195.09) mol Pt` atoms
`292.64 g Pt = (1)/(195.09) xx292.64 mol` atoms
`= 1.5 mol Pt`. Atoms
Formula method. Applying Eq, (1.7)we get,
Moles of Pt atoms `= ("Mass of Pt")/("Molar mass of Pt")`
`= (292.64 g)/(195.199 "g mol"^(-1))`
`= 1.5 mol Pt` atoms
conversion factor method. Use a suitable conversion factor, i.e.,
`underset(g)overset("mol")(uarr) ("1 mol Pt atoms")/(195.09 "g Pt")`
Thus, ? mol Pt atoms `= 293.64g Pt xx ("1 mol Pt")/(195.09 "g Pt")`
`= 1.5 "mol Pt atoms"`