One of the several oxides of tin found in the earthâs crust is 78.77% by mass tin. what is its empirical formula and name?

To determine the empirical formula of the compound given, we need to determine the ratio of each element in the compound. To do that we assume to have 100 grams sample of the compound with the given composition. Then, we calculate for the number of moles of each element. We do as follows:
         mass        moles
Sn     78.77       0.6636
O      21.23       1.3269

Dividing the number of moles of each element with the smallest value, we will have the empirical formula:

         moles                 ratio
Sn    0.6636          0.6636/0.6636 = 1
O     1.3269          1.3269/0.6636 = 2

The empirical formula would be SnO2.