Hydrate Formula

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.

Calculate the mass percentages of the elements in CO$_2$

Stupidium is a fictional element with 2 isotopes, $^35$St with a mass of 34.9567 g/mol, and $^39$St with a mass of 39.0095 g/mol. The molar mass of St is 35.9826 g/mol. What are the percent abundances of the isotopes?