Chemical Formulas and Moles

Chemical Formulas and Moles

Example: 1.water (C) every molecule of water contains 2 atoms of hydrogen & one atom of oxygen- 2 molecules of H2O would contain 4 atoms of hydrogen & 2 atoms of oxygen- 6.02 x 1023 molecules of H2O would contain 1.20 x 1024 atoms of hydrogen & 6.02 x 1023 atoms of oxygenA simpler way of writing this last statement would be:One mole of H2O molecules contains 2 moles of hydrogen atoms and one mole of oxygen atoms.The subscripts in a chemical formula can be read as the number of atoms of each element in one molecule of the compound, OR, the number of moles of each element in one mole of the compound.

CO2 contains 1 mole of C atoms and 2 moles O atoms.C2H5OH contains 2 moles of C atoms, 6 moles of H atoms, and 1 mole of O atoms.Sample Problems:1. How many moles of each element are in 3.0 moles of H3PO4?2.How many moles of oxygen are there in 0.025 moles of aluminum sulfate?

3.How many moles of oxygen atoms are there in 24.8 g of carbonic acid?

4.How many atoms of hydrogen are present in 0.700 moles of ammonium sulfate?

5.Determine the number of oxygen atoms found in 12.3 g of sulfuric acid.Percent Composition of a SubstanceUsing the chemical formula of a compound, it is possible to calculate the percent composition of each element within that compound.To do this, divide the mass of the element in one mole of the compound by the molar mass of the compound, than multiply by 100%.Calculate the percent composition of sugar C12H22O9