moles calculations

Question

How many moles of tin atoms are in a pure tin cup with a mass of 31.5 gg 

Answer 1

Hello, Maram,

I'll assume you mean 31.5g, not 31.5gg (Gigagrams?).

The atomic weight of tin (Sn) is 118.7. That provides a conversion factor of (1 mole Sn)/(118.7g Sn). To find moles of Sn, divide the mass of tin by the conversion factor:

31.5g Sn/(118.7 g Sn/mole Sn) Note how the grams cancel and the moles move to the top:

31.5/118.7 moles, or 0.265 moles of tin, to 3 sig figs.

Bob