Chemical Reactions Chapter 11

Law of Conservation of Mass Mass is conserved – not created or destroyed For chemical reactions, mass of products must equal mass of reactants. Matter is also conserved. Number of elements of products must equal number of elements of reactants.

Word Equations Chemical equations written in words. Word equations have the following pattern: reactant 1( ) + reactant 2( )  product 1( ) + product 2( ) Reactants begin the reaction and are on the left side. Products are the result of the reaction and are on the right side.

Equations Symbols  “yields” + “and” (s)“solid” (l)“liquid”states are written after (g)“gas”reactants and products (aq)“aqueous” (dissolved in water)

Equations Symbols

Catalyst Chemical that speeds up a reaction but is not used up in the reaction Written over the “yields” arrow in a reaction

Chemical Equations Written with chemical symbols and reaction symbols States of matter included after each reactant and product. Balanced on both sides to show matter being conserved. *unbalanced equation called skeleton equation

Balancing Chemical Equations Number of atoms of each element on the reactants side must equal the number of atoms of each element on the products side. To balance: 1.Count atoms of each element of reactants and list. Count atoms of each element of products and list. 2.Add coefficients before reactants and/or products to make both sides equal. 3.If there is an odd number of atoms of an element, start by balancing that element first.

Types of Chemical Reactions SynthesisA + B  AB DecompositionAB  A + B Single DisplacementA + BC  AC + B Double DisplacementAB + CD  AD + CB CombustionC n H n + O 2  CO 2 + H 2 O

Special Synthesis Reactions If water is a reactant…. MO + H 2 O  MOH NMO + H 2 O  oxyacid

Special Decomposition Reactions If the reactant is polyatomic… CarbonateMCO 3  MO + CO 2 HydroxideMOH  MO + H 2 O ChlorateMClO 3  MCl + O 2 If the reactant is an acid… Oxyacidoxyacid  NMO + H 2 O If reactant is not polyatomic or acid… compound  element + element

Special Single Replacement Reactions (element + compound  compound + element) Swap like ions unless water is the compound If element is group 1 or 2 metal… M + H 2 O  MOH + H 2 If element is transition metal… M + H 2 O  MO + H 2

Metal Activity Series Single replacement reactions can only happen if the metal element in the reactants is more reactive than the metal of the compound in the reactants. If the lone metal is more reactive than the metal in the compound, the more reactive metal will displace the other metal.

Double Replacement Reactions (compound + compound  compound + compound) Swap cations

Combustion Reactions Usually involve an organic compound reacting with oxygen to produce carbon dioxide and water. C n H n + O 2  CO 2 + H 2 O OR C n H n O + O 2  CO 2 + H 2 O