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Lesson 29 Types of Reactions

Lesson 29 Types of Reactions. Objectives: -         The student will list the five types of reactions. -         The student will classify reactions as one or more of the five types. -         The student will apply an activity series to determine if a reaction will take place.

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Lesson 29 Types of Reactions

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  1. Lesson 29 Types of Reactions Objectives: -         The student will list the five types of reactions. -         The student will classify reactions as one or more of the five types. -         The student will apply an activity series to determine if a reaction will take place. PA Science and Technology Standards: 3.4.10.A; 3.4.12.A; 3.1.10.C; 3.4.12.B; 3.4.10.B

  2. I.     Combustion a.      Most reactions used for energy are combustion reactions b.      Combustion – exothermic reaction that usually involves oxygen to form the oxides of the elements in a reactant. c.      Example                         i.      S8(s) + 8O2(g)  8SO2(g) + energy – this is the reaction which occurs on a match head when it lights                         ii.      CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) + energy – this is the reaction when methane burns iii. (C6H10O5)20 + 120O2 120CO2 + 100H2O + energy – this is the reaction when the rest of the paper in the match burns.

  3. d.   Often in combustion reactions, the products listed are not formed, because the reaction doesn’t progress to completion           i.      Sometimes CO is formed instead of CO2           ii.     Sometimes all of the carbon is not converted to carbon containing gases – this leaves ashes. Complete combustion usually requires extremely high temperatures.

  4. Combustion Hydrocarbon + Oxygen  Carbon dioxide + Water

  5. II. Synthesis a.      Synthesis – the process of building compounds from elementary substances through one or more chemical reactions b.      The key feature of synthesis reactions is that they are used in building more complex molecules from simpler ones. c.      Some reactions, such as the match head lighting above, fit more than one kind of reaction type – this one is both a synthesis reaction and a combustion reaction.

  6. d.     One specific type of synthesis reaction is polymerization               i.      To make cellulose or starch, a bunch of glucose molecules are attached together in a long chain.               ii.      Polymerization – a chemical reaction in which many simple molecules combine in chains to form a very large molecule.                iii.      Repeating simple units are called monomers, and the chains or molecules are called polymers.                iv.      Plastics, DNA, and the compounds mentioned above are examples of polymers.                v.      In some cases, the monomers are identical, like in most plastics – in other cases, the monomers are different, such as in DNA.

  7. Synthesis A + B  AB

  8. III. Decomposition a.      Decomposition - chemical reaction in which a single compound is broken down to produce two or more simpler substances. b.      Common products of decomposition reactions are CO2, O2, H2, and N2. c.      The key feature of decomposition reactions is that the reactant compound is broken down into two or more simpler compounds

  9. Decomposition AB  A + B

  10. III. Single Displacement a.      Elements trade places in single-displacement reactions (also sometimes known as single replacement reactions) i.      Single-displacement reaction – chemical reaction in which one element replaces another element in a compound                         ii.      Examples       Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)       2Al(s) + 3CuCl2(aq)  2AlCl3(aq) + 3Cu(s)       2K(s) + 2HOH(l)  2KOH(aq) + H2(g)

  11. b. An activity series summarizes and predicts reactions          i.      Two examples       2K(s) + 2HOH(l)  2KOH(aq) + H2(g)       Cu(s) + 2H2O  no reaction    ii.      Being able to write a chemical equation does not necessarily mean that the reaction will actually take place.                iii.      In order to determine if a reaction will take place, you must use an activity series.                iv.      Activity series – an arrangement of elements in the order of their tendency to react with water and acids.                v.      If an element higher up on the activity series is brought into contact with a compound containing a less active element, it will replace it in that compound in a single- displacement reaction.

  12. vi.    Example      * Potassium will replace hydrogen in water because it is higher up on the list than hydrogen * Copper will not replace hydrogen in water because it is lower than hydrogen on the list. • The activity series can be used to determine if a reaction will take place. It is not completely correct, but the exceptions are not worth noting. • You do not need to know the activity series – you need to know how to use it.

  13. c.     Controlling reactions with the activity series            i.      In general, the farther apart two elements are on the activity series, the more likely the higher one will replace the lower one in compounds.             ii.      Also, the greater the difference, the more violent the reaction. iii. This allows us to control specific reactions by coating certain metals such as iron with other metals like zinc, since zinc will react faster than iron

  14. Single Displacement A + BC  AC + B Or A + BC  BA + C

  15. V. Double Displacement a.       In double-displacement reactions, atoms are exchanged between compounds. b.      Double-displacement reaction – chemical reaction in which two elements in different compounds exchange places. c.       Example i.      2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq) d.      The main reason why this reaction occurs is because one of the products, PbI2, is not soluble in water, and falls out of solution. e.       You can treat these reactions as if the ions are all separated in solution, since this is what happens when these compounds are placed in solution.

  16. f. It would be better to show this reaction as follows:          i.      2K+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq)  PbI2(s) + 2K+(aq) + 2NO3-(aq)             ii.      Note that the K+ and NO3- ions do not actually participate in the reaction, because they appear in the same form on the left and the right of the reaction.             iii.      These non-participatory ions are called spectator ions.             iv.      Often, these reactions can be simplified by not showing the spectator ions, writing what is known as a net ionic equation.

  17. g.  Double displacement reactions always involve the formation either of a molecular compound such as water, or the creation of a gas or a precipitate.             i.      Combining acids and bases results in a double- displacement reaction 1.      Example a.       Mg(OH)2(aq) + 2HCl(aq)  MgCl2(aq) + 2H2O(l) b.      This is an example of Mg(OH)2, a base, neutralizing HCl, an acid. 2.      Acid/Base reactions always produce water and a salt. a.       Net ionic equation – OH-(aq) + H+(aq)  H2O(l)

  18. Double Displacement AB + CD  AD + CB

  19. Reaction Summary

  20. Five Classes of Reactions Virtual Lab 2 video

  21. Questions: • List the five types of reactions, and define each. • Indicate which of the five types each of the following reactions is: • Zn (s) + 2HCl (aq)  ZnCl2 (aq) + H2 (g) • C6H12O6 + 6O2 6CO2 + 6H2O • 2H2 + O2 2H2O • 2KI (aq) + Pb(NO3)2 (aq)  PbI2 (s) + 2KNO3 (aq) • 6CO2 + 6H2O  C6H12O6 + 6O2 • A reaction in which two element exchange places. • A reaction in which something is burned in oxygen. • A reaction in which something more complex is built up from several less complex things. • A reaction in which one more reactive element replaces one less reactive element in a compound. • A reaction in which a complex molecule is broken down into several simple compounds. • Having a campfire. • Plants converting oxygen and water, with energy from the sun, into sugar molecules. • Humans transforming sugar, in the presence of oxygen, into carbon dioxide and water.

  22. Indicate whether a reaction will occur or not in each of the following cases: • Li + ZnCl2 ? • Ni + CuSO4 ? • Cu + AlBr3 ? • Ca + KNO3 ? • Ba + HgOH  ? • Au + AgNO3 ? • Mg + Ca(OH)2 ?

  23. Reaction Prediction Problems For each of the following reactions, write a complete WORD equation. Beneath the word equation write a complete balanced equation, substituting chemical symbols for the words. Some of the examples will have substances which do not react. Indicate this by writing NR. 1.      potassium plus fluorine 2.      hydrogen plus oxygen 3.      magnesium plus hydrochloric acid 4.      calcium hydroxide plus hydrogen nitrate 5.      sulfur dioxide plus water 6.      methane (CH4) plus oxygen 7.      copper plus sulfuric acid

  24. 8.      aluminum plus hydrochloric acid 9.      sodium chlorate (heated) 10.      aluminum plus magnesium 11.      magnesium plus zinc periodate 12.      mercury plus oxygen (mercury (II) product formed) 13.      zinc chloride plus hydrogen sulfide 14.      silver chloride plus sodium perchlorate 15.      barium nitrate plus sodium chromate 16.      sodium bromide plus silver nitrate 17.  calcium phosphate plus aluminum sulfate 18.  zinc carbonate (heated)

  25. 19.      mercury I sulfate plus ammonium thiocyanate 20.      potassium sulfite plus zinc phosphate 21.      lithium oxide plus water 22.      sodium chloride (electrolysis) 23.      iron (II) hydroxide plus phosphoric acid 24.      dinitrogen pentoxide plus water 25.      sodium plus nitric acid 26.      iron (III) iodide plus copper (II) fluoride

  26. 27.      lead plus potassium chlorate 28.      sulfur plus oxygen 29.      sodium sulfate plus barium chloride 30.      ammonium phosphate plus lithium hydroxide 31.      mercury plus nitric acid (mercury (II) product is formed) 32.      sodium oxide plus water 33.      mercury (I) sulfate plus hydrochloric acid 34.      calcium carbonate plus lithium iodide 35.      bromine plus chlorine 36.  mercury II nitrate plus sodium dichromate 37.  water (electrolysis)

  27. 38.      cobalt (II) nitrate plus barium hydroxide 39.      ammonium sulfate plus calcium hydroxide 40.      mercury (II) oxide (heated) 41.      ammonium bromide plus aluminum chloride 42.      barium oxide plus water 43.      tin (IV) hydroxide plus nitric acid 44.      calcium plus oxygen 45.      magnesium plus phosphoric acid

  28. 46.      cadmium chloride plus ammonium hydroxide 47.      aluminum sulfide plus acetic acid 48.      strontium plus sulfur 49.      calcium plus aluminum bromide 50.      potassium hydroxide plus sulfuric acid

  29. DEMONSTRATIONS!!

  30. DOUBLE DISPLACEMENT • Pb(NO3)2(aq) + 2KI(aq)  PbI2(s) + 2KNO3(s)

  31. DECOMPOSITION • 2H2O2 2H2O + O2

  32. SINGLE DISPLACEMENT • Zn + 2HCl  ZnCl2 + H2

  33. SYNTHESIS • 2H2 + O2 2H2O

  34. COMBUSTION! • 2C3H8O + 9O2 6CO2 + 8H2O • CH4+ 2O2 CO2 + 2H2O

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