Chemical Equations and Reactions

1. Chemical Equations and Reactions

2. Chemical Equations • Law of Conservation of Matter • Matter is neither created nor destroyed, only changed in form. • Law of Mass Balance • For any given chemical change: Σ Mass Reactants = Σ Mass Products

3. Chemical Equations • Types of Chemical Equations • Molecular Equations 3H2(g) + N2(g) 2NH3(g) Mg(s) + O2(g) MgO(s) 2KClO3(s) + Heat 2KCl(s) + 3O2(g) Pb(NO3)2(aq) + 2NaI(aq) 2NaNO3(aq) + PbI2(s)

4. Chemical Equations • Types of Chemical Equations • Molecular Equation HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) • Ionic Equations H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) Na+(aq) + Cl-(aq) + H2O(l) • Net Ionic Equations H+(aq) + OH-(aq) H2O(l)

5. Chemical Equations • Thermochemical Equations • The Exothermic Reaction Eqations • N2(g) + 3H2(g) 2NH3(g); ΔHRxn = -91.8 Kj • N2(g) + 3H2(g) 2NH3(g) + 91.8 Kj • The Endothermic Reaction Equations • H2O(l) H2O(g); ΔHRxn = 44 Kj • H2O(l) + 44 Kj H2O(g)

6. Chemical Equations • Ionization Equations • Oxidation (loss of electrons) • Nao(g) Na+(g) + e- • [e- on product side of equation indicates ‘loss’ of electron by oxidation] • Reduction (gain of electrons) • Clo(g) + e- Cl-(g) • [e- on reactant side of equation indicates ‘gain’ of electron by reduction]

7. Chemical Equations Word Equations • magnesium + nitrogen gas → magnesium nitride • hydrogen + bromine → hydrogen bromide • sodium oxide _ethyne + oxygen → carbon dioxide + water • acetic acid + calcium carbonate → calcium acetate + water + carbon dioxide • aluminum + iron(III) oxide → iron + aluminum oxide • aluminum + copper(II) chloride → copper + aluminum chloride • copper(II) chloride + sodium carbonate → sodium chloride + copper(II) carbonate

8. Chemical Equations • Classification of Chemical Reactions • Oxidation/Reduction Reactions • Composition A + B AB • Decomposition AB A + B • Single Replacement A + BX AX + N • Metathesis Reactions • Double Replacement AX + BY AY + BX • Combustion Reactions • Hydrocarbons + O2(g) CO2(g) + H2O(g)

9. Chemical Equations • Decomposition – Composition Reactions AB A + B • (Number Product Compounds > no. Reactant Compounds) A + B AB • (Number Product Compounds < no. Reactant Compounds) In general, composition reactions are simply decomposition reactions in reverse.

10. Chemical Equations • Decomposition/Compostion Reactions • Chlorates >>>> Salt + Oxygen • Oxides of Metals >>> Metal + Oxygen • Acids (Weak Oxoacids) >>> Nonmetal Oxide + HOH • Carbonates, Sulfates & Nitrates >>> Nonmetal Oxide + Metal Oxide • Hydroxides >>> Metal Oxide + HOH • Electrolytic Decomposition >>> Basic Elements in Standard State

11. Chemical Equations • Predict the products of the following: • KClO3(s) + Heat >>> ? • Fe2O3(s) + Heat >>> ? • H2CO3(aq) + Heat >>> ? • CaCO3(aq) + Heat >>> ? • Ca(OH)2(aq) + Heat >>> ? • NaBr(aq) + Electricty >>> ?

12. Chemical Equations • Single Replacement Reactions (1o Reactions) A + BX AX + B • Driving force in the single replacement reaction is the replacement of a metalli with a more active metallic element. • Replacement follows activity as listed on the ‘Activiy Series’.

13. Chemical EquationsThe Activity Series

14. Chemical EquationsThe Activity Series and 1o Reactions • Predict the products of the following: • Mgo(s) + CuCl2(aq) (?) • Zno(s) + AgNO3(aq) (?) • Pbo(s) + CaI2(aq) (?) • Sno(s) + AlCl3(aq) (?)

15. Chemical EquationsOxidation & Reduction Process in Single Replacement Reactions • Oxidation Process ≡ The transfer (loss) of e-’s during chemical reaction process to form Cations. Metal (Cation)+ + e- Lio(g) Li+(g) + e- Cao(g) Ca2+(g) + 2e- Alo(g) Al3+(g) + 3e-

16. Chemical EquationsOxidation & Reduction Process in Single Replacement Reactions • Reduction Process ≡ The gain of e-’sinto the atomic valence level during chemical reaction process. Nonmetal* + e- (Anion)- Po(g) + 3e- P3-(g) So(g) + 2e- S2-(g) Bro(g) + e- Br-(g) *NOTE: Typically, nonmetal elements are used to illustrate the formation of anions through the reduction process. However, keep in mind that metallic ‘Main Group Elements’ are subject to gaining electrons and functioning as anions also, especially the metalloid elements.

18. Oxidizing Agents and Reducing Agents: Oxidizing Agents ≡ Substances that cause another substance to undergo oxidation. Reducing Agents ≡ Substances that cause another substance to undergo reduction. Zno(s) Zn+2(aq) + 2e- is an oxidation process, but Zinc is a reducing agent. Cu+2(aq) + 2e-Cuo(s) is a reduction process, but Copper(II) is an oxidizing agent. Reducing Agent Oxidizing Agent

19. Chemical EquationsThe Double Replacement Reactions and The Metathesis Process • The Double Replacement Reaction ( 2oRxn ) AX + BY AY + BX • Characteristics • Ionic Exchange Reaction. • Oxidation states do NOT change during process. • Driving force of reaction is the tendency to form a more stable product substance; i.e., solid ppt, liquid wk electrolyte, or gas decomposition product. (The ‘Driving Force’ prevents the reaction from reversing during process.)

20. A+ X- + B+ Y- A+ Y- + (BX) IONIC DRIVING FORCE 2NaCl(aq) + Pb(NO3)2(aq) 2NaNO3(aq) + [ PbCI2(s) ] [1(+2)+2(-1)] 2[1(+)+1(-)] 2[(+1)+(-1)] [1(+2)+2(-1)] Driving Force Compound – Is not shown in ionic form.

21. Chemical EquationsEquations from Metathesis Rxns Molecular Equation: Ionic Equation: Net Ionic Equation: 2NaCl(aq) + Pb(NO3)2(aq) 2NaNO3(aq) + PbCI2(s) 2Na+ (aq) + 2Cl- (aq) + Pb+2(aq) + 2NO3-(aq) 2Na+ (aq) + 2NO3-(aq) + PbCI2(s) 2Na+ (aq) + 2Cl- (aq) + Pb+2(aq) + 2NO3-(aq) 2Na+ (aq) + 2NO3-(aq) + PbCI2(s) Spectator Ions Pb+2(aq) + 2Cl-(aq) PbCI2(s) Typically, the cation (metal) is listed first & followed by the anion (nonmetal). The ‘driving force’ products are NOT shown in Ionic form.

22. Predict the products resulting from mixing the following ionic compounds.Write and balance • The molecular equation • The ionic equation • The net ionic equation • Sodium Phosphate + Calcium Nitrate >>>> ?