2All chemical reactions have two partsReactants - the substances you start withProducts- the substances you end up withThe reactants turn into the products.Reactants ® Products
3In a chemical reaction The way atoms are joined is changed Atoms aren’t created or destroyed.Can be described several waysIn a sentenceCopper reacts with chlorine to form copper (II) chloride.In a word equationCopper + chlorine ® copper (II) chloride
4Symbols used in equations Table 11.1the arrow separates the reactants from the productsRead “reacts to form”The plus sign = “and”(s) after the formula -solid(g) after the formula -gas(l) after the formula -liquid
5Symbols used in equations (aq) after the formula - dissolved in water, an aqueous solution. used after a product indicates a gas (same as (g))¯ used after a product indicates a solid (same as (s))
6Symbols used in equations indicates a reversible reaction (More later)shows that heat is supplied to the reactionis used to indicate a catalyst used in this case, platinum.
7What is a catalyst?A substance that speeds up a reaction without being changed by the reaction.Enzymes are biological or protein catalysts.
8Skeleton Equation Uses formulas and symbols to describe a reaction doesn’t indicate how many.All chemical equations are sentences that describe reactions.
9Convert these to equations Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form solid iron (II) chloride and hydrogen sulfide gas.
10Convert these to equations Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water.
14Balanced Equation Atoms can’t be created or destroyed All the atoms we start with we must end up withA balanced equation has the same number of atoms of each element on both sides of the equation.
15® O + C O C O O C + O2 ® CO2 This equation is already balanced What if it isn’t already?
16® C C O O C O C + C + O2 ® CO We need one more oxygen in the products. Can’t change the formula, because it describes what actually happens
17® C C O C O C O + O Must be used to make another CO But where did the other C come from?Must have started with two C2 C + O2 ® 2 CO
18Rules for balancingWrite the correct formulas for all the reactants and productsCount the number of atoms of each type appearing on both sidesBalance the elements one at a time by adding coefficients (the numbers in front)Check to make sure it is balanced.
19Never Change a subscript to balance an equation. If you change the formula you are describing a different reaction.H2O is a different compound than H2O2Never put a coefficient in the middle of a formula2 NaCl is okay, Na2Cl is not.
20Example R P H O 2 1 4 4 2 2 H2 + H2O O2 ® 2 H2 + H2O O2 ® The equation is balanced, has the samenumber of each kind of atom on both sidesRecountChanges the OMake a table to keep track of where youare atNeed twice as much O in the productAlso changes the HNeed twice as much H in the reactant
21Example R P 4 2 H 2 4 2 O 1 2 This is the answer 2 H2 + O2 ® 2 H2O Not this2O12
27TechniquesIf an atom appears more than once on a side, balance it last.If you fix everything except one element, and it is even on one side and odd on the other, double the first number, then move on from there.C4H10 + O2 CO2 + H2O
28Predicting the Products Types of ReactionsPredicting the Products
29Types of Reactions There are too many reactions to remember Fall into categories.We will learn 5 types.Will be able to predict the products.For some we will be able to predict whether they will happen at all.Must recognize them by the reactants
30#1 Combination Reactions Combine - put together2 elements, or compounds combine to make 1 compound.Ca +O2 ® CaOSO3 + H2O ® H2SO4We can predict the products if they are two elements.Mg + N2 ®
50#3 Single ReplacementWhat does it mean that Ag is on the bottom of the list?
51#3 Single Replacement Nonmetals can replace other nonmetals Limited to F2 , Cl2 , Br2 , I2The order of activity is that on the table.Higher replaces lower.F2 + HCl ®Br2 + KCl ®
52#4 Double Replacement Two things replace each other. Reactants must be two ionic compounds or acids.Usually in aqueous solutionNaOH + FeCl3 ®The positive ions change place.NaOH + FeCl3 ® Fe3+OH- + Na+Cl-NaOH + FeCl3 ® Fe(OH)3 + NaCl
54#4 Double Replacement Will only happen if one of the products doesn’t dissolve in water and forms a solidor is a gas that bubbles out.or is a covalent compound usually water.Polyatomic ions don’t change from side to side
55Complete and balance assume all of the reactions take place. CaCl2 + NaOH ®CuCl2 + K2S ®KOH + Fe(NO3)3 ®
56Complete and balanceKOH + Fe(NO3)3 ®H3PO4 + Ca(OH)2 ®
57How to recognize which type Look at the reactantsE for elementC for compoundE + E CombinationC DecompositionE + C Single replacementC + C Double replacement
58Last TypeCombustionA compound composed of only C H and maybe O is reacted with oxygenIf the combustion is complete, the products will be CO2 and H2O.If the combustion is incomplete, the products will be CO and H2O.or just C and H2O.O2 will always be the second reactant
59ExamplesComplete combustion of C4H10Incomplete combustion of C4H10
60ExamplesComplete combustion of C6H12O6Incomplete combustion of C2H6O
61Ionic Compounds and acids Fall apart into ions when they dissolveThat’s why they conduct electricity when dissolved.So when we write them as (aq) they are really separatedNaCl(aq) is really Na+(aq) and Cl-(aq)K2SO4 (aq) is really K+(aq) and SO42-(aq)
62Reactions in aqueous solutions Many reactions happen in solutionMakes it so the ions separate so they can interact.Solids, liquids, and gases are not separated, only aqueous
63Complete Ionic Equation Every aqueous compound is written as separate ionsSolids, liquids and gases as whole compoundsMgCl2(aq) + PbSO4(aq) → MgSO4(aq) + PbCl2(s)Is reallyMg2+(aq) + Cl-(aq) + Pb2+(aq) + SO4(aq) → Mg2+(aq) + SO4(aq) + PbCl2(s)
64Write the complete ionic equation for FeBr3(aq) + KOH(aq) → KBr (aq) + Fe(OH)3(s)Fe3+(aq)Br-(aq)K+(aq)OH-(aq)K+(aq)Br-(aq)Fe(OH)3(s)+++→++
65Write the complete ionic equation for CaCl2(aq) + MgSO4(aq) → CaSO4(s) + MgCl2(aq)
66Write the complete ionic equation for Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + HOH(l)
67The complete ionic equation is Fe3+(aq)+ Br-(aq) + K+(aq) +OH-(aq) → K+(aq) +Br-(aq) + Fe(OH)3(s)K+ and Br- don’t change.They are spectator ionsCould be eliminatedFe3+(aq) +OH-(aq) →Fe(OH)3(s)This is what really changes
68Net ionic equationShows only those particles that change before and after.Eliminate spectator ionsNeeds to be balanced in terms of both mass and chargeFe3+(aq) +OH-(aq) →Fe(OH)3(s)Fe3+(aq) +3 OH-(aq) →Fe(OH)3(s)
69Write the net ionic equation HCl (aq) + Ba(OH)2 (aq) → BaCl2(s) + HOH (l)
70Write the net ionic equation Al + FeSO4(aq) → Al2(SO4)3(aq) + Fe
71Write the net ionic equation Cl2(s) + NaI(aq) → NaCl(aq) + I2(s)
72Write the net ionic equation K2CO3(aq) + MgI2(aq) → MgCO3(s) + KI(aq)
73Net ionic equationsWritten for single and double replacement.
74Predicting precipitates Solids formed from aqueous solution.You can predict them if you know some general rules for solubility.
75These things are soluble Salts with alkali metals and ammoniumSalts of nitrates and chloratesSalts of sulfates except Ag+, Pb2+, Hg22+, Ba2+, and Sr2+Salts of chlorides except Ag+, Pb2+, and Hg22+
76These things are insoluble Carbonates, phosphates, chromates, sulfides, and hydroxidesUnless they fall under rule # 1
77Is it soluble?LiBrBa(NO3)2CaSO4PbCl2CaCO3K2CO3Cd(ClO3)2
78Is there a reaction?For double replacement- has to make gas, solid or water.Water from an acid- H+ and a hydroxide- OH- makes HOHSolids- from solubility rulesExchange ions and see if something is insoluble
79Is there a reaction?MgSO4 + NaOH →H2SO4 + KOH →K3PO4 + FeF3→
81An equation Describes a reaction Must be balanced to follow the Law of Conservation of MassCan only be balanced by changingthe coefficients.Has special symbols to indicate state, and if catalyst or energy is required.
82Reactions Come in 5 types. Can tell what type they are by the reactants.Single Replacement happens based on the activity seriesDouble Replacement happens if the product is a solid, water, or a gas.
83The Process 1. Determine the type by looking at the reactants. 2. Put the pieces next to each other based on type3. Use charges to write the formulasElements get 2?4. Use coefficients to balance the equation.