Mass Percent Composition

A white powder used in paints, enamels and ceramics has the following percentage composition: Ba (69.6%), C (6.09%), and O (24.3%). What is the empirical formula?

Given a molar mass of 116.24 g/mol and an empirical formula of C$_3$H$_8$N, find the molecular formula for this compound.

A sample of a liquid with a mass of 8.657 g was decomposed into its elements and gave 5.217 g of C, 0.9620 g of H and 2.478 g of O. What is the percentage composition of each element in this compound?

What is the formula for the following hydrate:

3.71 g Na$_2$CO$_3$ , 6.29 g H$_2$O