Chemical Reactions - NJCTL

Slide 1 / 142Slide 2 / 142Chemical ReactionsSlide 3 / 142Slide 4 / 142Table of Contents: Chemical Reactions· Chemical EquationsClick on the topic to go to that section· Balancing EquationsChemical Equations· Types of Chemical Reactions· Precipitation Reactions· Net Ionic Equations· Oxidation-Reduction Reactions· Types of Oxidation-Reduction ReactionsReturn toTable ofContents· Acid-Base Reactions· Identifying Reaction Types: SummarySlide 5 / 142Slide 6 / 142Chemical EquationsChemical equations are concise representations ofchemical reactions.Chemical EquationsThe formulas of the reactants (on the left) are connected by anarrow with the formulas of the products (on the right).To write a word equation, write the names of the reactants to theleft of the arrow separated by plus signs.Write the names of the products to the right of the arrow, alsoseparated by plus signs. -- 2O2(g) -- CO2(g) CH4(g)Reactant Reactant2H2O(g)Product Product

Slide 7 / 142Slide 8 / 142Symbols used in chemical equationsSkeleton equationsA skeleton equation is a chemical equation that does not indicatethe relative amounts of the reactants and products.Write the formulas of the reactants to the left of the yields sign(arrow) and the formulas of the products to the right.Here is the equation for rusting:Metallic Iron reacts with oxygen in the airto produce iron (III) oxide (rust).Iron( metal) Oxygen( gas) iron (III) oxideFe O # Fe O2Slide 9 / 14223( solid)(word equation)( skeleton /chemical equation)Slide 10 / 1421 In the reaction CH O # H O COthe products are:Word Equations4 (g)When ignited, methane gas reacts with oxygen gasto produce carbon dioxide and steam.2 (g)2(g)2 (g)A oxygen and waterB carbon dioxide and waterC oxygen and methaneCO gasO2 gasD methane and carbon dioxideH O gas22EThis "skeleton" equation is not balanced:CH4 (g) OI don't know the answer to this.H O CO2 (g)2(g)2 (g)Slide 11 / 142Slide 12 / 1422 In the reaction CH O # H O COthe products are:4 (g)2 (g)2(g)Word equations to Chemical equations2 (g)A solidsSolid potasium chlorate decomposes in air to produce solidpotassium chloride and oxygen gas.B liquidsThe word equation is:C gasespotasium chlorate (s) -- potassium chloride (s) oxygen (g)Ecannot be determinedFI don't know how to answer this.answerD dissolved in water (aqueous)The unbalanced "skeleton" equation is:KClO3(s)KCl(s) O2(g)answerCH4 gas

Slide 13 / 142Slide 14 / 142Word equations to Chemical equationsLaw of Conservation of MassWrite the word equation, then the skeleton equationAluminum sulfate reacts with calcium chloride toproduce calcium sulfate and aluminum chlorideAluminum sulfate calcium chloride -- calciumaluminum chlorideSlidefor sulfateWord equationSlide for Skeleton equationAl (SO ) CaCl -- Ca(SO ) AlCl24 324“We may lay it down as an incontestable axiomthat, in all the operations of art and nature,nothing is created; an equal amount of matterexists both before and after the experiment.Upon this principle, the whole art of performingchemical experiments depends.”--Antoine Lavoisier, 17893Slide 15 / 142Slide 16 / 142Balancing chemical equationsBalancing EquationsTo write a balanced chemical equation, first write the skeletonequation. Then use coefficients to balance the equation so that itobeys the law of conservation of mass.This is a balanced equation for making a bicycle. The numbersare called coefficients—small whole numbers that are placed infront of the formulas in an equation in order to balance it.Return toTable ofContentsSlide 17 / 142Slide 18 / 142Balancing chemical equationsCH1C4H4 (g) 2O2 (g)4OReactants appear on theleft side of the equation.#CO2 (g) 2HO21C2O(g)2O4HProducts appear on theright side of the equation.The states of the reactants and products are written in parenthesesto the right of each compound.Balancing chemical equationsCH4 (g) 1C4H2 O2 (g)4O#CO2 (g) 1C2O2 H2O (g)2O4HCoefficients are inserted to balance the equation.

Slide 19 / 142Slide 20 / 142Subscripts and Coefficients3 How many oxygen atoms are in one formulaunit of calcium nitrate? (First, write the formulafor calcium nitrate.)A 2answerB 3C 5D 6Subscripts tell the number of atoms of each element in amolecule.ECoefficients tell the number of representative particles(atoms, molecules, or formula units).I don't know how to answer this.Slide 21 / 142Slide 22 / 142answer4 How many nitrogen atoms are in one formulaunit of ammonium sulfate?Slide 23 / 142Balancing chemical equationsWrite a balanced chemical equation for this reaction.First write a skeleton equationSlide 24 / 142Balancing chemical equationsThen, count up the number of each type of element oneach side of the reactionCl NaBr # # Br NaCl2chlorine sodium bromide # bromine sodium chlorideCl NaBr # # Br NaCl222ReactantsProductsCl: 2Cl: 1Na: 1Na: 1Br: 1Br: 2

Slide 25 / 142Slide 26 / 142Balancing chemical equationsBalancing chemical equationsNext, identify one element that is not balanced. It is best to startwith an easy element. The fewer places an element appears onboth sides of a reaction, the easier it will be to balance.Identify the side that needs more of that particular element.Cl NaBr # # Br NaCl2Cl NaBr # # Br NaCl2Reactants2Products2ReactantsProductsCl: 2Cl: 1Cl: 2Cl: 1Na: 1Na: 1Na: 1Na: 1Br: 1Br: 2Br: 1Br: 2Slide 27 / 142Slide 28 / 142Balancing chemical equationsDetermine which molecule or element will be getting thecoefficient. In this case, because we need more chlorine on theproducts side, we will have to add a coefficent to the NaCl, sincethat is the only product containing chlorine.Balancing chemical equationsTo figure out what the coefficient should be, simply take the amount ofthat specific element you need from the molecule, and divide by theamount of the element you have in the molecule.Cl NaBr # # Br NaCl2Cl: 2Cl NaBr # # Br NaCl22ReactantsProductsCl: 2Na: 1Cl: 1Na: 1Br: 1Na: 1Br: 1Br: 22Cl: 22ReactantsProductsCl: 2Na: 1Cl: 1Na: 1Br: 1Na: 1Br: 1Br: 22Need Have12If this is not a whole number, simply multiply ALL the substancesin the reaction by some whole number to make the coefficientswhole numbers.Slide 29 / 142Balancing chemical equationsNow, just reevaluate the amount of each element on the tableSlide 30 / 142Balancing chemical equationsContinue with these steps until all the elements are balanced.When all the elements exist in equal amounts on both sides of theequation, you have a balanced chemical equation.Cl NaBr # # Br 2NaCl2Cl: 22ReactantsProductsCl: 2Na: 1Cl: 1 2Na: 1Br: 1Na: 1 2Br: 1Br: 2Cl 2NaBr # # Br 2NaCl2Cl: 22ReactantsProductsCl: 2Na: 1Cl: 1 2Na: 1 2Br: 1Na: 1 2Br: 1 2Br: 2

Slide 31 / 142Slide 32 / 142Balancing chemical equationsSPECIAL NOTE: Make sure that when you are calculating yourcoefficents you are only looking at the amounts needed/had byindividual elements or moleculesCH3OH O2 # # CO2 2H2OH: 4Br: 1H: 2 4O: 1 2 3O: 2 1 3 2 2 4ReactantsCl: 2ProductsC: 1CH3OH O2 # # CO2 2H2OC: 1H: 4Br: 1H: 2 4O: 1 2 3O: 2 1 3 2 2 44Need Have3Slide 33 / 142Balancing chemical equationsBalancing chemical equationsSPECIAL NOTE: Remember to make sure you get ridof ALL fractions.CH3OH O2 # # CO2 2H2OReactantsCl: 2H: 4Br: 1H: 2 4O: 1 2 3O: 2 1 3 2 2 44-1Need Have232CH3OH 2x 2 O2 # # 2CO2 2x2H2OProductsC: 1Because we already have 1 Oxygenfrom CH3OH, we only need 3 Oxygenfrom O2Because O2 only has 2 Oxygen, thedenominator must be 2.Cl: 2ReactantsC: 1 2H: 4 8Br: 1H: 2 4 8O: 1 2 3 2 6 8O: 2 1 3 2 2 4 4 4 832Balancing chemical equationsIf you follow these steps, you'll be able to balance anytype of reaction.Cl: 2ReactantsProductsC: 1 2Na: 1C: 1 2H: 4 8Br: 1H: 2 4 8O: 1 2 3 2 6 8O: 2 1 3 2 2 4 4 4 8ProductsC: 1 2Na: 1Slide 35 / 1422CH3OH 3O2 # # 2CO2 4H2OWRONG!!!Slide 34 / 142SPECIAL NOTE: Here is the correct way to evaluatethe coefficent in this caseC: 1Na: 1ProductsC: 1Na: 1Slide 36 / 1425 When the following equation is balanced, thecoefficients are:Na O2 #Na2OA 1, 1, 1B 1, 2, 4C 4, 1, 2D2, 2, 1E 4, 1, 4answerReactantsCl: 2C: 1Na: 1Balancing chemical equationsSPECIAL NOTE: Here is the incorrect way to evaluate thecoefficent in this case

Slide 37 / 142Slide 38 / 1426 When the following equation is balanced, thecoefficients areHgO #Hg 7 When the following equation is balanced, thecoefficients areO2Al A 1, 1, 1ZnCl #answeranswerD 2, 2, 1C 2, 3, 2, 3D 1, 3, 1, 2E 2, 3, 3, 2E 4, 1, 4Slide 39 / 142Slide 40 / 1429 When the following equation is balanced, thecoefficients are8 When the following equation is balanced, thecoefficients are2NaI CaCl2NH3 O2 #NO2 A 1, 1, 1, 1answerB 3, 2, 2, 3C 2, 3, 2, 3B 4, 7, 4, 6C 2, 3, 2, 3D 1, 3, 1, 2D 1, 3, 1, 2E 2, 1, 2, 1E 4, 3, 4, 3Slide 41 / 142Slide 42 / 14210 When the following equation is balanced, thecoefficients areNa S #2Al S 23Reaction TypesMost reactions can be classified as one of the following:NaNO3Precipitation: formation ofinsoluble product out ofaqueous solutionsC 1, 1, 1, 1D 4, 6, 3, 2E 2, 3, 2, 3answerA 2, 3, 1, 6B 2, 1, 3, 2H2OOxidation/Reduction:exchange of electronsbetween atoms/ionsAcid/Base: reactionbetween acids and basesanswerCaI #A 1, 1, 1, 13 33B 4, 7, 4, 6C 4, 1, 2Al(NO ) AlClA 1, 1, 1, 1B 1, 2, 4NaCl Zn 2

Slide 43 / 142Slide 44 / 142Precipitation ReactionsPrecipitation ReactionsThe giant clam's shell is made from the precipitation of CaCO3Return toTable ofContentsSlide 45 / 142Slide 46 / 142Precipitation ReactionsPrecipitation ReactionsPrecipitation reactions involve the reaction of water soluble ioniccompounds to form a water insoluble product called a precipitate:One must know which ionic compounds are water soluble and whichare not. It is the insoluble ones that form precipitates!Some general rules apply:AgNO3(aq) HCl(aq) -- AgCl(s) HNO3(aq)ALWAYS SOLUBLESOMETIMES SOLUBLEAgCl precipitateINSOLUBLENH4 , C2H3O2-, ClO3-, Group 1 A metal ions, NO3-Cl-,Br-, I- except when combined with Ag , Hg ,and Pb2 SO42- except when combined with Ag , Hg , Pb2 ,Ca2 , Sr2 , Ba2 CO32-, PO43-, OH-, S2-, F-, O2-(unless paired with asoluble ion)Slide 47 / 142Slide 48 / 142Na2CO3NH4NO3AgNO3Mg(OH)2KCl12 Which of the following would be MOST SOLUBLE nswer11 Which one of the following would be INSOLUBLE inwater?

Slide 49 / 142Slide 50 / 142Solubility ChartSolubilitiesA solubilitychartprovidesmore exactinformationas to theindividualsolubilities ofvarious ionicsubstances.Note that S on this chartmeans that thecompound is soluble.When you write achemical equation, it willbe (aq) aqueous.Insoluble compounds areshown with the letter I.When you write achemical equation, it willbe (s) solid.Slide 51 / 142Double Displacement ReactionsPrecipitation reactions are often called "double replacement" or"double displacement" reactions because it appears as if the ionsswitch places with each other.Slide 52 / 142Precipitation ReactionsSome examples of precipitation reactions.Pb(NO3)2(aq) 2 KI(aq) # PbI2(s) 2 KNO3(aq)AgNO (aq) KCl(aq) # AgCl(s) KNO (aq)3NaCl(aq) AgNO3(aq)-- AgCl(s) NaNO3(aq)Na and Ag switch placesSlide 53 / 142Precipitation ReactionsA precipitation reaction will NOT occur if both products are watersoluble.2NaNO3(aq) MgCl2(aq) -- 2NaCl(aq) Mg(NO3)2(aq)3The formation of an insoluble precipitate is the drivingforce of these reactionsSlide 54 / 142Precipitation ReactionsPredict the products of this reaction:potassium phosphate magnesium chloride -- K3PO4 (aq) MgCl2 (aq) -- KCl AnswerMg3(PO4)2Now, put in the phases of the productsand balance the equation.Since both products are soluble, no reaction occurs2K3PO4 (aq) 3MgCl2 (aq)-- 6KCl(aq) Mg3(PO4)2(s)Answer