Chemical Formulas

One of the compounds of iron and oxygen occurs naturally in the mineral magnetite. When a 2.447 g sample was analyzed it was found to have 1.771 g of Fe. Calculate the empirical formula of this compound.
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\(_2\)
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
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?
Naturally occurring boron is composed of 19.8% of \(^{10}\)B and 80.2% of \(^{11}\)B. Atoms of \(^{10}\)B have a mass of of 10.0129 u and those of \(^{11}\)B have a mass of 11.0093 u. Calculate the average atomic mass of boron.
The nuclear power industry extracts \(^6\)Li but not \(^7\)Li from natural samples of lithium. As a result, the average molar mass of commercial samples of lithium is increased. The current abundace of the two isotopes are 7.42% and 95.58% respectively, and the masses of their atoms are 9.968 x 10\(^{-24}\) g and 1.165 x 10\(^{-23}\) g. What is the current molar mass of a natural sample of lithium?