2The Importance of Chemical Reactions: Many chemical reactions occur naturally, although some take place so slowly that we do not notice them.
3Biochemical Reactions The natural chemical reactions that we observe occurring in living things are known as biochemical reactions.2 important chemical reactions are shown below:Respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energyPhotosynthesis: 12H2O + 6CO2 + energy C6H12O6 + 6H2O + 6O2
4Manufacture Important Chemicals Many important chemicals are created through chemical reactions.Examples: Fertilizers, cement, plastics, synthetic textiles, and pharmaceuticals.
5Harmful Chemical Reactions There are also chemical reactions that harm living organisms and harm the environment.(See RAFT assignment)
6Review Chemical Reactions: Indicator that a chemical change has occurred:Other signs of a chemical change:Change in electrical conductivityChange in melting point or boiling pointChange in densityChange in taste
7Types of Chemical Reactions A reaction occurs when two or more molecules interact and a chemical change occurs. A chemical change MUST occur in order for a chemical reaction to occur.Chemical reactions start with the reactants and go to the products.
8Synthesis/ Combination: A synthesis reaction is when two or more simple compounds combine to form a more complicated one. These reactions come in the general form of:A + B ---> AB
9Synthesis/ Combination: One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide:8 Fe + S8 --->
10Decomposition:A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form:AB ---> A + B
11Decomposition:One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas:2 H2O--->
12Single displacement:This is when one element trades places with another element in a compound. These reactions come in the general form of:A + BC ---> AC + B
13Single displacement:One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas:
14Single displacement: The Activity Series: The activity series of an element is used to determine whether or not a single displacement reaction will occur.
15Single displacement:Each metal will displace any metal ion that appears below it in the series.The Activity SerieslithiumThese metals displace hydrogen from waterpotassiumbariumcalciumsodiummagnesiumThese metals displace hydrogen from acidsaluminumzincironnickeltinleadhydrogencopperThese metals do not react with acids or pure watermercurysilvergold
17The Halogen Displacement Series Single displacement:The Halogen Displacement SeriesThe Halogen Displacement SeriesEach halogen willdisplace any halideion that appears below itfluorinechlorinebromineiodine
18Single displacement:Examples: determine whether a reaction will occur, if so, what are the products?Br2(aq) NaCl(aq) Zn(s) + NiCl2(aq) I2(aq) KF(aq) F2(aq) KI(aq) Cu(s) AgNO3(aq)
19Double displacement:This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form:AB + CD ---> AD + CB
20Double DisplacementOne example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate:
21Double DisplacementHow can we predict when a double displacement reaction will occur? Such reactions usually result in the formation of a precipitate, a gas, or water.
22Acid Base HA + BOH ---> H2O + BA This is a special kind of double displacement reaction that takes place when an acid and base react with each other. The H+ ion in the acid reacts with the OH- ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water:HA + BOH ---> H2O + BA
23Acid BaseOne example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide:
25Combustion:A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of reaction is the burning of napthalene:C10H O2 --->
26Steps to determine types of reactions: Follow this series of questions. When you can answer "yes" to a question, then stop!1) Does your reaction have oxygen as one of its reactants and carbon dioxide and water as products? If yes, then it's a combustion reaction2) Does your reaction have two (or more) chemicals combining to form one chemical? If yes, then it's a synthesis reaction3) Does your reaction have one large molecule falling apart to make several small ones? If yes, then it's a decomposition reaction4) Does your reaction have any molecules that contain only one element? If yes, then it's a single displacement reaction5) Does your reaction have water as one of the products? If yes, then it's an acid-base reaction6) If you haven't answered "yes" to any of the questions above, then you've got a double displacement reaction
27AssignmentSee types of reactions assignment (Pg 24)