Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18General Chemistry Topic 5:Chemical Reactions and Equations1. Understand the concept of the mole and appreciate its importance in chemical reactions.2. Be able to write simple chemical formulas, balance simple chemical reactions, and do simple quantitative calculations involving chemical reactions. 3. Know how to calculate molecular/formula weights and how to convert grams to moles. 4. Know Avogadro’s number and appreciate its significance. ObjectivesPhysical change: appearance of a substance is altered but not its composition. For example, boiling water, melting ice, breaking glass.Chemical reaction: atoms of reacting substances form new combinations with new physical properties. Chemical ReactionsChemical EquationsA chemical equation must show:•The number of moles of each reactant and each product, using coefficients.•The direction of the reaction, using an arrow(s).Optionally, a chemical equation may show physical states of reactants and products (s, solid; l, liquid; g, gas, aq, aqueous).Optionally, a chemical equation may show whether energy (Δ) is taken up or released in the reaction. A chemical equation describes how all atoms in reactants are recombined in products.CH4 + 2O2 CO➞2 + 2H2Ocoefficient coefficientreactants productsChemical Equations•Chemical equations must be balanced.•Matter cannot be either gained or lost in a reaction.•The total mass of reactants must equal the total mass of products.•The number of moles of each atom must be the same on both sides of the equation.Chemical EquationsChemical equations must be balanced.HCl + Ca CaCl➞2 + H2Not balanced Reactants1 mol H atoms1 mol Cl atoms1 mol Ca atomsProducts2 mol H atoms2 mol Cl atoms1 mol Ca atomsH2Cl2 + Ca CaCl➞2 + H2Balanced BUT INCORRECT. H2Cl2 is not same as HCl. 2HCl + Ca CaCl➞2 + H2Balanced and CORRECT.Balancing Chemical EquationsCa3(PO4)2 + H2SO4 CaSO➞4 + H3PO4calcium sulfuric calcium phosphoricphosphate acid sulfate acidBegin with the most complex formula, starting with an element that appears in only one formula on both sides.Ca3(PO4)2 + H2SO4 ➞ 3CaSO4 + 2H3PO4Balance the remaining atoms.Ca3(PO4)2 + 3H2SO4 ➞ 3CaSO4 + 2H3PO46 H+3 SO42–Poll Everywhere QuestionWhat are the coefficients for the following chemical reaction:w NH3 + x O2 ⟶ y N2 + z H2O When poll is active , respond at PollEv.com/refriedorText REFRIED to 22333 once to joinAnswer in the following format:5,3,2,7w NH3 + x O2 ⟶ y N2 + z H2O2NH3 + x O2 ⟶ y N2 + 2H2O2NH3 + O2 N⟶2 + 3H2O2NH3 + 3O2 N⟶2 + 6H2O4NH3 + 3O2 ⟶ 2N2 + 6H2Ow and z must be at least 2to account for 2O and 2N onthe left and right, respectively. But if w is 2, z has to be at least 3.Now we have 3O on the rightbut 2O on the left. To resolvethe O’s, we multiply the left O by 3and the right O by 2. Now we have 12H on the rightbut 6 on the left. To resolve,we multiply the left NH3 by 2. Wealso have to multiply the N2 by 2.How many molecules of nitrogen (N2) are produced when 36.5 g of NH3 react in the equation we just balanced? Atomic masses: N = 14, H = 1, O = 16.Molecular weight of NH3 = 14 + 3(1) = 17. Thus, 1 mole NH3 = 17 g36.5 g NH3 x 1 mole/17g = 2.15 moles 1 mole of NH3 yields 0.5 mole N2. Thus, 2.15 moles NH3 will yield 1.07 moles N2.1.07 moles x 6.023 X 1023 molecules/mole = 6.44 X 1023 molecules of N2.Answer4NH3 + 3O2 2N⟶2 + 6H2ONa + Cl2 NaClCu2O + O2 CuOAl + O2 Al2O3Na + Cl2 + O2 NaClO4C4H8 + O2 CO2 + H2OAl + Cl2 AlCl3Mg + AgNO3 Mg(NO3)2 + AgCaCO3 CaO + CO2HgO Hg + O2Homework: Balance the following equations.2Na + Cl2 2NaCl2Cu2O + O2 4CuO4Al + 3O2 2Al2O32Na + Cl2 + 4O2 2NaClO4C4H8 + 6O2 4CO2 + 4H202Al + 3Cl2 2AlCl3Mg + 2AgNO3 Mg(NO3)2 + 2AgCaCO3 CaO + CO2 OK as is!2HgO 2Hg + O2Homework: Balance the following equations.We can read the equation for this reaction several ways:1 atom of carbon and 1 molecule of oxygen react to form 1 molecule of carbon dioxide.1 mole of carbon and 1 mole of molecular oxygen react to form 1 mole of carbon dioxide.12.0 g of carbon and 32.0 g of oxygen react to form 44.0 g of carbon dioxide (molar masses).6.02 x 1023 atoms of carbon and 6.02 x 1023 molecules of oxygen react to form 6.02 x 1023 molecules of carbon dioxide.Chemical Reactions: Molecules, Moles, GramsC + O2 CO2Consider the chemical reaction:+Combination Reaction: two or more atoms or compounds combine to form one new product.Decomposition Reaction: reactant splits into two or more simpler products.Replacement Reaction: elements in a compound are replaced by other elements.Types of Chemical ReactionsS + O2 SO2CaCO3 CaO + CO2Zn + CuSO4 ZnSO4 + Cu (single)BaCl2 + Na2SO4 BaSO4 + 2 NaCl (double)NaOH + HCl NaCl + H2O (double)Oxidation-reduction reactions are important. Examples include photosynthesis, biological energy production, formation of rust, and burning natural gas.Oxidation-Reduction ReactionsOxidation-reduction reactions are defined as a loss and a gain of electrons among the reactants.Oxidation and reduction ALWAYS occur together, never one without the other.The atom or compound that loses electron(s) is said to be oxidized.The atom or compound that gains electron(s) is said to be reduced.In the formation of an ionic compound (NaCl, CaS), the metal loses electrons to become a cation while the nonmetal gains electrons to become an anion.The metal is oxidized and the nonmetal is reduced.More aboutbiological ox-redsoon (IMPORTANT!)Example of an oxidation-reduction reactionCa + S Ca++ + S-2 (CaS)Ca Ca++ + 2e- (oxidized = loss) S + 2e- S-2 (reduced = gain)oxidizedreducedSimultaneousand balanced(lost e- have togo somewhere!)Ca + S CaSChemical equation (can you write and balance them?)Chemical Reactions Combination reaction Decomposition reaction Substitution reaction (single versus double)OxidationReductionCan you do molar and mass calculations for a chemical reaction if you know the amount of one component (and have a Periodic Table)?Can you tell which reactant is oxidized and which reduced if given the oxidation-reduction