175.24g of strontium equals how many moles

Using dimensional analysis, we can find the moles of strontium by comparing the mass of strontium to it's atomic mass.
You can find the atomic mass of Sr on the periodic table:
Atomic Mass Sr = 87.62g/mol

In case you are not familiar, dimensional analysis works like this:
(what we know) x (conversion factor) = what we are looking for

The conversion factor compares the units of what we know to the units of what we are looking for. In this case, the conversion factor is:
1 mol/87.62g

The important thing to note about the conversion factor is that you want to be able to cancel out the units of your given measurement (in this case, it is the mass)

So, our full solution will be:
moles Sr = (175.24 g)x(1 mol/87.62 g)
(cancel out the mass units)
moles Sr = 175.24 x 1 mol/87.62
= 2.00 mol Sr

Hope this helped you!