Slide 1Chemical EquationsBalancing EquationsBalancing EquationsFormula and Molecular MassPercent CompositionThe MoleMolar MassSlide 9Chapter 3 1Stoichiometry:Calculations with Chemical Formulas and EquationsChapter 3 2Chemical EquationsChemical equations are concise representations of chemical reactions.Chapter 3 3Balancing EquationsIf an element is present in just one compound on each side of the equation, try balancing that element first.Balance any reactants or products that exist as the free element last.In some reactions, certain groupings of atoms (such as polyatomic ions) remain unchanged. In such cases, treat these groupings as a unit.Chapter 3 4Balancing EquationsAt times, an equation can be balanced by first using frac tional coefficients. The fraction is then cleared by multiplying each coefficient by a common factor.Chapter 3 5Formula and Molecular MassThe formula mass is the sum of the atomic masses for the atoms in a chemical formula.The molecular mass is the sum of the atomic masses of the atoms in a molecule.Chapter 3 6Percent CompositionThe percent composition of a compound is the percentage by mass contributed by each element in the compound.€ % element =(number of atoms)(atomic mass)(formula mass of the compound)×100The MoleOne mole (mol) is the amount of substance that contains as many elementary entities as there are atoms in exactly 12 g of the carbon-12 isotope.Chapter 3 7Molar MassThe molar mass of a substance is the mass of one mole of that substance.Numerically equal to the atomic mass, molecular mass, or formula mass, but with units of g/mol.Chapter 3 8Chapter 3 9A compound is found to have a composition of 30.04% phosphorus and 69.96% sulfur by mass. Determine its empirical