Chemistry 103OutlineTypes of FormulasEmpirical & Molecular FormulasRelating Molecular and Empirical FormulasFinding the Molecular FormulaMolecular FormulaChemical ReactionsPhysical ChangeChemical ChangeChemical ReactionSlide 12Evidence of a Chemical ReactionWriting a Chemical ReactionChemical EquationsSymbols Used in EquationsChemical Equations Are BalancedSlide 18Slide 19Balanced Chemical EquationsExample - making ammoniaSlide 22Slide 23Slide 24Slide 25Slide 26Slide 27Balancing EquationsThe Numbers in Chemical EquationsMore Practice: Balancing ReactionsStoichiometryQuantities in a Chemical ReactionSlide 33Moles in EquationsConservation of MassLaw of Conservation of MassSlide 37Writing Mole-Mole FactorsCalculations with Mole FactorsMole relationsChemistry 103Lecture 14OutlineI. Empirical/Molecular FormulasII. Chemical Reactions - basic symbols - balancing - classificationIII. StoichiometryThe molecular formula Is the true or actual number of the atoms in a moleculeThe empirical formula Is the simplest whole number ratio of the atoms (this is the formula for ionic compounds) H2O2HOmolecular formula empirical formulaTypes of FormulasEmpirical & Molecular FormulasIonic Compounds - Only need Empirical formula.Molecules - Need information on both to determine exact make-up of your systemMolecular Formula Empirical Formula C6H6CHA molecular formula Is a multiple (or equal) of its empirical formulaHas a molar mass that is the empirical mass multiplied by a whole numbermolar mass = a whole number empirical massIs obtained by multiplying the empirical formula by a whole numberRelating Molecular and Empirical FormulasDetermine the molecular formula of compound that has a molar mass of 78.11 g/mole and an empirical formula of CH. Finding the Molecular FormulaA compound is 24.27% C, 4.07% H, and 71.65% Cl. The molar mass is known to be 99.0 g. What are the empirical and molecular formulas? Molecular FormulaChemical ReactionsPhysical ChangeIn a physical change,•The identity and composition of the substance do not change•The state can change or the material can be torn into smaller piecesCopyright © 2005 by Pearson Education, Inc.Publishing as Benjamin CummingsChemical ChangeIn a chemical change, •Reacting substances form new substances with different compositions and properties•A chemical reaction takes placeCopyright © 2005 by Pearson Education, Inc.Publishing as Benjamin CummingsChemical ReactionIn a chemical reaction,Old bonds are broken and new bonds are formed Atoms in the reactants are rearranged to form one or more different substancesFe and O2 form rust (Fe2O3)Chemical ReactionIn a chemical reaction, •A chemical change produces one or more new substances •There is a change in the composition of one or more substancesCopyright © 2005 by Pearson Education, Inc.Publishing as Benjamin CummingsEvidence of a Chemical ReactionChanges that can be seen are evidence of a chemical reaction.Writing a Chemical ReactionChemists use a shorthand approach when writing the specifics of a chemical reaction. This approach is called the chemical equation. Reactants -----> ProductsChemical EquationsA chemical equation, •Gives the chemical formulas of the reactants on the left of an arrow and the products on the right Reactants ProductC(s)O2 (g)CO2 (g)Symbols Used in EquationsSymbols used in chemicalequations show: The states of the reactantsThe states of the productsThe reaction conditionsChemical Equations Are BalancedIn a balanced chemical reaction,•Atoms are not gained or lostChemical Equations Are BalancedIn a balanced chemical reaction,•The number of reactant atoms are equal to the number of product atomsChemical Equations•Chemical equations: symbolic descriptions of chemical reactions.•Two parts to an equation: •reactants and productsH2 + O2  H2OA Chemical Equation must also be “balanced”. 2H2 + O2 --> 2H2OBalanced Chemical EquationsChemical Equations must be balancedThere must be equal numbers of atoms of each element on both sides of the equation (both sides of the arrow)1. Write the correct symbols and formulas for all of the reactants and products.2. Count the number of each type of atom on BOTH sides of the equation. 3. Insert coefficients until there are the equal numbers of each kind of atom on both sides of the equation.Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state.Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) NH3 (g)Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) NH3 (g)Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) NH3 (g)Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) 2 NH3 (g)Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. 3 H2(g) + N2(g) 2 NH3 (g)Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. BEFORE AFTER 3 H2(g) + N2(g) 2 NH3 (g)Balancing EquationsMethane reacts with oxygen (combustion reaction) to form carbon dioxide and water.Write a properly balanced chemical equationThe Numbers in Chemical EquationsMore Practice:Balancing Reactions C2H6 + O2  CO2 + H2O C3H6 + O2  CO2 + H2O NH3 + O2  NO + H2OStoichiometryChemical Stoichiometry: using mass and quantity relationships among reactants and products in a chemical reaction to make predictions about how much product will be made.4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)Four molecules NH3 react with five molecules O2 to produce four molecules NO and six molecules H2OQuantities in a Chemical Reaction4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)Four molecules NH3 react with five molecules O2 to produce four molecules NO and six molecules H2OandFour mol NH3 react with five mol O2 to produce four mol NO and six mol H2OQuantities in a Chemical ReactionWe can read the equation in “moles” by placing the word “mole” or “mol”