6Representing Chemical Equations reactant 1 + reactant 2 → product 1 and product 2producesProduct(s) must be different than the reactants
7Representing Chemical Equations Simply a “recipe”→Eggs and butter and flour produce a cakeWord equations name the reactants and products.What is missing from this recipe?AMOUNTS!!!
8Representing Chemical Equations →Iron (II) and oxygen produce iron oxideFe (s) + O2 (g) → FeO (s)What is missing?Amounts!How do you figure out the amounts needed and produced?
9Balancing Equations Based on the Law of Conservation of Mass “Matter is not created or destroyed in a reaction, just rearranged.”Fe + O-O → Fe OWhat is wrong here?an oxygen atom is missing
10Balancing Equations Atom inventory Fe + O2 → Fe O Reactant side Product sideFe O Fe OFe + O2 → Fe OFinal equation: Fe + O2 → Fe O222222
11Balancing Equations Steps: 1. Write the skeleton equation (can’t escape formula writing)2. Count atoms in reactants3. Count atoms in products4. Change coefficients to make atom counts match. Never change subscripts.5. Reduce coefficients if necessary.
12Practice Problems ____ AlBr3 + ____ K ____ KBr + ____ Al ____ P4 + ____ Br2 ____ PBr3____ P Br2 4 PBr3
13Symbols used in Equations + separates two reactants or two products→ “Yields” separated reactants from productsDesignates a reactant in the solid stateDesignates a reactant in the liquid state(g) Designates a reactant in the gaseous state(aq) Designates a reactant in the aqueous state→ → indicates that heat is supplied to a reaction→ Indicates that a catalyst is used (here, platinum)heatPt
14Symbols used in Equations #1 separates two reactants or two products#2 “Yields” separated reactants from products#3 Designates a reactant in the solid stateDesignates a reactant in the # 4 state(g) Designates a reactant in the # 5 state#6 Designates a reactant in the aqueous state# 7 indicates that heat is supplied to a reaction→ Indicates that a # 8 is used (here, platinum)# 9 name the diatomic elementsPt
15Classifying Chemical Reactions Five general typesSynthesis one new productSolid sodium and chlorine gas form solid sodium chloride 2Na(s) + Cl2(g) → 2NaCl(s)→
16Classifying Chemical Reactions Combustion Must have O2 as a reactant2 Mg + O2 → 2 MgO→Combustion reactions are exothermic; energy is produced.
17Classifying Chemical Reactions Combustion of hydrocarbons (compounds containing hydrogen and carbon)CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)Most fuels are hydrocarbons
18Classifying Chemical Reactions Decomposition Only one reactantHydrogen peroxide decomposes to release oxygen gas and leave water on your skinH2O2(aq) → O2 (g) + H2O(l)2 H2O2(aq) → O2 (g) + 2 H2O(l)
19Classifying Chemical Reactions Single replacement reactions One reactant is an elementCopper reacts with silver nitrate to produce silver and copper nitrate.Cu(s) + AgNO3(aq) → Ag(s) + Cu(NO3)2(aq)
20Single replacement reactions Activity Series of MetalsLithium IronRubidium NickelPotassium TinCalcium LeadSodium CopperMagnesium SilverAluminum PlatinumManganese GoldZincDecreasesDecreases
22Classifying Chemical Reactions Double replacement reactions both reactants are ionic compoundsA gas, liquid, or solid must be producedSilver nitrate and sodium chloride react to produce sodium nitrate and silver chlorideAgNO3 (aq) + Na Cl (aq) → NaNO3 (aq) + AgCl (s)Ag+Cl-Na NO3-Na NO3-AgCl
23Summary Reaction Classification Class of ReactionReactantsProbable productsSynthesisTwo or more substancesOne compoundCombustionSome substance and oxygenAn oxideH20 and CO2 for hydrocarbon combustionDecompositionTwo or more (elements or compounds)Single-replacementAn element and a compoundA new compound and the replaced elementDouble-replacementTwo compoundsTwo different compounds including a s, l, g
24Reactions in Aqueous Solutions Review:Solution – homogeneous mixtureSolute – substance dissolvedSolvent – most plentiful substance in the solutionWater is the “universal solvent”Other substances can also be solvents
25Reactions in Aqueous Solutions How does water dissolve ionic compounds? Water is a polar molecule.
26Reactions in Aqueous Solutions Reactions that form solids Lead nitrate and potassium iodideTwo clear solutions – mix – precipitateformsPb +2NO3 -K+I-
27Reactions in Aqueous Solutions Reactions that form solids What happened on an atomic level?→Lead and iodide form a new compoundNitrate and potassium are still dissolved ions – they did nothing but “watch” – spectator ionsNO3 –Pb +2K+I-K+NO3 –PbI2
28Reactions in Aqueous Solutions Reactions that form solids Complete ionic equationPb NO3 - + K+ + I- → PbI2 + NO3 - + K+Spectator ionsNet ionic equationPb I- → PbI2