ans: 0.0735 mol
-to go from grams to moles we multiply:
grams (mol/grams)
-grams will cancel and we will be left with moles.
-Plug in your values; the atomic mass of tin (Sb) is 118.7g. (one mol of tin is equal to 118.7g):
8.72g (1 mol/118.7g) = 0.07346251
-since 1 mole of tin is equal to 118.7g, this is just like multiplying the initial value by 1; we are, in fact, not changing the number. Just converting to another unit of measure.
-round to the least number of significant digits (3 sig fig) and we end with 0.0735 mol.