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.

C. definite shape, definite volume. that is a solid.

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.