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 the arrow separates the reactants from the productsRead “reacts to form”YieldsThe 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)) (products only)¯ used after a product indicates a solid (same as (s)) (products only)
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.A catalyst lowers the activation energyActivation Energy- minimum amount of energy required by reacting particles in order to form the activated complex and lead to a reaction
8Skeleton Equation Uses formulas and symbols to describe a reaction doesn’t indicate how many.All chemical equations are sentences that describe reactions.
10Balanced 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.
11® O + C O C O O C + O2 ® CO2 This equation is already balanced What if it isn’t already?
12® 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
13® 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
14Rules 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.
15Never 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.
16Example 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
17Example R P 4 2 H 2 4 2 O 1 2 This is the answer 2 H2 + O2 ® 2 H2O Not this2O12
23TechniquesIf 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
24Predicting the Products Types of ReactionsPredicting the Products
25Types 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
26#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 ®
46#3 Single ReplacementWhat does it mean that Ag is on the bottom of the list?
47#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 ®
48#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
50#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
51Complete and balance assume all of the reactions take place. CaCl2 + NaOH ®CuCl2 + K2S ®KOH + Fe(NO3)3 ®
52Complete and balanceKOH + Fe(NO3)3 ®H3PO4 + Ca(OH)2 ®
53How to recognize which type Look at the reactantsE for elementC for compoundE + E CombinationC DecompositionE + C Single replacementC + C Double replacement
54Last 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
55ExamplesComplete combustion of C4H10Incomplete combustion of C4H10
56ExamplesComplete combustion of C6H12O6Incomplete combustion of C2H6O
57Ionic 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)
58Reactions 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
60An 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.
61Reactions 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.
62The 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.