2 Chemical Equation Describes chemical reaction. Chemical equation: reactants yield productsReactants ProductsMuch easier to write symbols and formulas instead of words
3 Examples CH4(g) + O2(g) CO2(↑) + H2O(↑) Solid Iron reacts with oxygen gas to form the solid IronIIIoxide.iron(s) + oxygen(g) ironIIIoxide(s)Fe(s) + O2(g) Fe2O3(s)Carbon tetrahydride gas BURNS to form carbon dioxide gas and water vapor.Carbon tetrahydride(g) + oxygen(g) carbon dioxide(↑) + water(↑)CH4(g) + O2(g) CO2(↑) + H2O(↑)Skeleton Equation: chemical equation that tells you what the reactants and products are but NOT how much of each you have.First step in writing a chemical equation.
4 Symbols Used (s) solid (l) liquid (g) gas (↑) gas as a product (aq) aqueous (in water solution)() ppt (precipitate) solid product from 2 aqueous reactantsD means with heatPt means with Platinum catalyst: speeds up a reaction without being used. reversible reaction
5 Balancing Chemical Equations Balanced equations have:the same # of atoms of each element on BOTH sides of the equation.Law of Conservation of Mass – atoms can neither be created nor destroyed, simply rearranged.
6 Rules for Balancing Equations Get the correct formulas for reactants and products.(USE ION CHART AND DON”T FORGET DIATOMIC ELEMENTS!)Write reactants on left, products on right. Use plus signs to separate compounds and yield sign to separate the reactants from products.
7 Rules ContinuedCount the # of atoms of each element in reactants and products. (Polyatomic atoms on both sides count as one.)Balance # of each element using coefficients.Coefficient – small whole # in front of a formula.NEVER CHANGE FORMULA SUBSCRIPTS
8 Rules for Balancing Equations Balance elements appearing 3 or more places LAST.Check each element to make sure equation is balanced.Make sure all coefficients are in the lowest whole number ratio.Do not change subscripts!!!
9 H O N Cl Br I F Diatomic Molecules There are 7 naturally occurring Diatomic Molecules- a molecule made up two atoms of the same element. They are only diatomic when they are alone.There are 7 naturally occurringdiatomic molecules.H O N Cl Br I F
11 5 Types of Chemical Reactions Combination Reaction – elements combine to form a compound.A + B ABelement + element compoundEx. Sodium + chlorine sodium chloride___Na(s) + ___ Cl2(g) ___ NaCl(s)22
12 5 Types of Reactions AB A + B compound element + element Decomposition Reaction – compound breaks down into its element.AB A + Bcompound element + elementEx: MercuryII oxide mercury + oxygen___ HgO ___Hg + ___O222
13 AB + C A + CB or AB + D AD + B 5 Types of Reactions - 3 Single Replacement Reaction – one element replaces another element in a compound.AB + C A + CBorAB + D AD + B
14 Examples of Single Replacement Reactions Must use Activity Series to see if reaction worksZinc + sulfuric acid zinc sulfate + hydorgenZn(s) + H2SO4(aq) ZnSO4(aq) + H2(↑)Periodic table is activity series for halogensSodium bromide + chlorine sodium chloride + bromine___NaBr(s) + ___Cl2(g) ___NaCl(s) + ___Br2(↑)22
15 AB + CD AD + CB 5 Types of Reactions Double Replacement Reaction – two compounds react and exchange positive ions to form two new compounds.AB + CD AD + CBBarium Chloride(aq) + potassium carbonate(aq) barium carbonate() + potassium chloride(aq)BaCl2(aq) + K2CO3(aq) BaCO3() + ___ KCl(aq)2
16 CxHy + O2 CO2 + H20 5 Types of Reactions Combustion Reaction – oxygen reacts with a compound composed of C and H.CxHy + O CO2 + H20Also called Burning (exothermic)The products are always CO2 and H2O.
17 Examples of Combustion Reactions C6H O CO H2O7½63C6H O CO H2OCH3OH O CO H2O1½2CH3OH O CO H2O
18 Special Decomposition Reactions: Decomposition of a Carbonate:Metal carbonate metal oxide + carbon dioxideXCO XO + CO2ex. Na2CO Na2O + CO2
19 Special Decomposition Reactions: Decomposition of a Hydroxide:Metal hydroxide metal oxide + waterXOH XO + H2Oex. 2NaOH Na2O + H2O
20 Special Decomposition Reactions: Decomposition of a Chlorate: (ClO3)Metal chlorate metal chloride + oxygenXClO XCl + O2ex ___NaClO ___NaCl + ___O223
21 Special Decomposition Reactions: 4 Special single Replacement Reaction:Group IA or IIA metal and H2OX + HOH XOH + H2ex. 2Na + 2HOH NaOH + H2
22 How to ID types of reactions. Combination Reactions – given 2 items that form 1 new compound.Decomposition Reactions – given a single compound that breaks into parts.Single Replacement – given a single element plus a single compound, forms a new compound a a different element.Double Replacement – given two compounds (+’s change places).Combustion Reaction – given CH compound with Oxygen, always forms water and carbon dioxide.