1 / 94

Predicting Reactions

Predicting Reactions. Presented by Mr. Mark Langella AP Chemistry Instructor College Board Consultant And Dr. Robert Gamper AP Chemistry Instructor 9/9/2014. Why do the reactions occur?. Gibbs Free Energy drives the Spontaneous reactions Lower PE energy

mala
Download Presentation

Predicting Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Predicting Reactions Presented by Mr. Mark Langella AP Chemistry Instructor College Board Consultant And Dr. Robert Gamper AP Chemistry Instructor 9/9/2014 Sponsored by PWISTA.com

  2. Why do the reactions occur? • Gibbs Free Energy drives the Spontaneous reactions • Lower PE energy • Formation of Stronger Bonds • Greater Entropy ( Formation of Gases) • Solubility • Formation Constant Sponsored by PWISTA.com

  3. Ways of Expressing CHEMICAL EQUATIONS • Word equation • In word equations, the names of the reactants and products are written out. The following example is a word equation: • carbon + oxygen carbon dioxide Sponsored by PWISTA.com

  4. Formula equations • Formula equations consist of formulas substituted for the names in the word equation. The reaction above becomes • C + O2 CO2 Sponsored by PWISTA.com

  5. Ionic equations • In ionic equations, all water soluble compounds in an aqueous solution are separated into ions. • 2NaI(aq) + Pb(NO3)2(aq) 2NaNO3(aq) + PbI2(s) • 2Na+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) 2Na+(aq) + 2NO3-(aq) + PbI2(s) • Spectator ions - Spectator ions do not participate in the chemical reaction. That is, they are identical on both sides of the equation. Sponsored by PWISTA.com

  6. Net ionic equations • The net ionic equation contains all of the particles in the ionic equation less any spectator ions. • 2Na+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) 2Na+(aq) + 2NO3-(aq) + PbI2(s) • Pb2+(aq) + 2I-(aq) PbI2(s) Sponsored by PWISTA.com

  7. Changes to Format • 3 questions, no choices • The equations will still be "net ionic" as they always have been, just balanced. • There will, as the acorn book also states, be a small question about the reaction that the student will have to answer. • The exact point values are not determined yet, the majority of the weight for each part will be on the balanced equation, rather than on the question. • The stems of the questions in some cases contain a little more guidance than we have seen in the past--for example, the equation on this year's question 4 that involves the addition of hydrochloric acid to silver chloride next year will be asked in such a way that the students are guided toward the formation of a complex. • The questions are simple things like what our students already are seeing on the multiple choice. • Posted on AP Central soon . Look for it there. Sponsored by PWISTA.com

  8. Changes to Format • The scoring changes have reduced the weight of this section to about 5% of the overall points available on the exam. • The student must write the balanced net ionic equation and then answer a question about the reaction. •  Points would be given for correct reactants, correct products, correct balancing, and the correct answer to the question asked. • The majority of the points available will be given for the correct balanced equation. Sponsored by PWISTA.com

  9. Examples • 1. A strip of magnesium metal is added to an aqueous solution of silver nitrate.        Question: Which substance is oxidized in the reaction?2. Solid potassium chlorate is strongly heated.        Question: What is the oxidation number of chlorine before and after the reaction occurs?3. Solid silver chloride is added to a solution of concentrated hydrochloric acid to form a complex ion.        Question: Which species acts as a Lewis base in the reaction?  Explain.4.  A solution of ethanoic (acetic) acid is added to a solution of barium hydroxide.        Question: Explain why a mixture of equal volumes of equimolar solutions of acetic acid and barium hydroxide is basic. Sponsored by PWISTA.com

  10. Examples • 5. Ammonia gas is bubbled into a solution of hydrofluoric acid.        Question: Identify a conjugate acid-base pair in the reaction.6. Zinc metal is placed into a solution of copper (II) sulfate.        Question: Describe the change in color that the original solution undergoes as the reaction proceeds.7. Hydrogen phosphide (phosphine) gas is added to boron trichloride gas.        Question: Which species acts as a Lewis acid in the reaction? Explain. Sponsored by PWISTA.com

  11. Examples • 8. A solution of nickel (II) bromide is added to a solution of potassium hydroxide.        Question: Identify the spectator ions in the reaction mixture.9. Hexane is combusted in air.        Question: When one molecule of hexane is completely combusted, how many molecules of products are formed? • http://apcentral.collegeboard.com/members/article/1,3046,151-165-0-52321,00.html Sponsored by PWISTA.com

  12. Balancing • We were reminded (especially by the combustion reaction above) that the coefficients used for balancing should be the lowest possibleWHOLE NUMBER coefficients.   • All other rules for the balanced equations are the same - omit spectator ions, assume a reaction occurs, write the formulas for molecular compounds (e.g. HF) as undissociated species in solution, etc. Sponsored by PWISTA.com

  13. Synthesis or Combination Reactions • In synthesis or combination reactions, two or more substances combine together to form a single product. • The general form is A + B C • The products must contain only those elements found in the reactants. Sponsored by PWISTA.com

  14. Sponsored by PWISTA.com

  15. Metal + Nonmetal Salt • Magnesium ribbon is burned in oxygen • A strip of magnesium metal is heated strongly in pure nitrogen gas Sponsored by PWISTA.com

  16. Online Demos • Reaction of Magnesium and Oxygen • http://boyles.sdsmt.edu/magburn/magnesium_burning.htm • Reaction of Iron and Sulfur • http://www.pc.chemie.uni-siegen.de/pci/versuche/english/v21-1.html • Reaction of Potassium and Oxygen • http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/page08.htm • Reaction of Lithium and Oxygen • http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/page02.htm • Reaction of Lithium and Chlorine • http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/page04.htm • Reaction of Sodium and Oxygen • http://neon.chem.ox.ac.uk/vrchemistry/FilmStudio/alkalimetals/HTML/page05.htm • Reaction of Zinc and Sulfur • http://boyles.sdsmt.edu/znsulf/zincsul.htm Sponsored by PWISTA.com

  17. Nonmetal + Nonmetal Molecular compounds • Pure Solid Phosphorus (White Form) is burned in air • Reaction of Phosphorus and Chlorine • Website: http://boyles.sdsmt.edu/pwithcl/reaction_of_white_phosphorus_and.htm • Reaction of Hydrogen and Oxygen • Website: http://www.chem.uiuc.edu/clcwebsite/balloon.html Sponsored by PWISTA.com

  18. Sponsored by PWISTA.com

  19. Hydrides • Preparation of the Group 1 hydrides • These are made by passing hydrogen gas over the heated metal. For example, for lithium hydride: Sponsored by PWISTA.com

  20. Nonmetal Oxide + Water Oxyacid • Oxy Acid= Contains H+ ions attached to common Polyatomic ion of Nonmetal Oxide plus one more oxygen • Solid dinitrogen pentoxide is added to water • Sulfur trioxide gas is bubbled into water Sponsored by PWISTA.com

  21. Phosphorus(V) oxide powder is sprinkled over dis­tilled water • Sulfur dioxide gas is bubbled into distilled water Sponsored by PWISTA.com

  22. Sponsored by PWISTA.com

  23. Metal oxide + water metal hydroxide • Solid Cesium Oxide is added to water • Solid sodium oxide is added to distilled water • Powdered strontium oxide is added to distilled water • Calcium oxide powder is added to distilled water • Solid barium oxide is added to distilled water Sponsored by PWISTA.com

  24. Demo Sponsored by PWISTA.com

  25. Sponsored by PWISTA.com

  26. Nonmetal Oxide and Metal Hydroxide • ) Reaction of Carbon Dioxide and Limewater • Website: http://boyles.sdsmt.edu/respira/respir.htm • CO2(g) + Ca(OH)2(l)  CaCO3(s) + H2O(l) Sponsored by PWISTA.com

  27. Sponsored by PWISTA.com

  28. Hydrogen-Nonmetal + Water Acidic Solution • Hydrogen Chloride gas bubbled into water Sponsored by PWISTA.com

  29. Metal oxide + nonmetal oxide metal ion attached to common polyatomic ion • Metal oxide + carbon dioxide metal carbonate • Carbon dioxide gas is passed over hot, solid sodium oxide • Metal oxide + sulfur dioxide Metal sulfite • Sulfur Dioxide is passed over solid calcium oxide Sponsored by PWISTA.com

  30. DECOMPOSITION REACTIONS • Substances break down by means of decomposition reactions • The general form of a decomposition reaction is • C A + B • Decomposition reactions are the opposite of combination or synthesis reactions Sponsored by PWISTA.com

  31. Decomposition of Metal Carbonate • Heating a metal carbonate always yields the metal oxide and carbon dioxide. • MCO3 MO + CO2 • Powdered magnesium carbonate is heated strongly • Solid calcium carbonate is strongly heated Sponsored by PWISTA.com

  32. Metal Hydrogen Carbonate Decomposition • Heating a metal bicarbonate gives the metal oxide, carbon dioxide, and water. • MHCO3 MO + H2O + CO2 • http://www.chemguide.co.uk/inorganic/group1/compounds.html • Solid Sodium Hydrogen Carbonate is strongly heated Sponsored by PWISTA.com

  33. Heating the nitrates • Most nitrates tend to decompose on heating to give the metal oxide, brown fumes of nitrogen dioxide, and oxygen. • For example, a typical Group 2 nitrate like magnesium nitrate decomposes like this: • In Group 1, lithium nitrate behaves in the same way - producing lithium oxide, nitrogen dioxide and oxygen. • The rest of the Group, however, don't decompose so completely (at least not at Bunsen temperatures) - producing the metal nitrite and oxygen, but no nitrogen dioxide. Sponsored by PWISTA.com

  34. Decomposition of Metal Hydroxides • Heating a metal hydroxide gives the metal oxide and water • MOH MO + H2O Sponsored by PWISTA.com

  35. Metal Sulfite Decomposition • Heating a metal sulfite produces a metal oxide and sulfur dioxide • MSO3 MO + SO2 • Solid calcium sulfite is heated in a vacuum Sponsored by PWISTA.com

  36. Metal Chlorate Decomposition • Heating a metal chlorate gives the metal chloride plus oxygen. • MClO3 MCl + O2 • Shortcut to Combustion of a peanut M&M • Burning Gummi Bears • Website: http://www.webct.com/service/ViewContent?contentID=1249557&communityID=858&categoryID=1249537&sIndex=0 Sponsored by PWISTA.com

  37. Electrolysis of Binary Compound • Electrolysis of a molten salt (ionic compound) separates the substance into its elements. • MN M + N Sponsored by PWISTA.com

  38. Ammonium Compound Decomposition • Ammonium Carbonates • Solid ammonium carbonate is heated • Ammonium Hydroxide Sponsored by PWISTA.com

  39. Sponsored by PWISTA.com

  40. Ammonium Dichromate Volcano • Website: http://www.chem.uiuc.edu/clcwebsite/ammvol.html • Decomposition of Ammonium Dichromate • Website: http://boyles.sdsmt.edu/dichrom/amdichr.htm • (NH4)2Cr2O7(s)  Cr2O3(s) + N2(g) + 4H2O(g) Sponsored by PWISTA.com

  41. Peroxide Decomposition • Elephant’s Toothpaste • Website: http://boyles.sdsmt.edu/tpaste/elephants.htm • Genie in a Bottle Demo • Website: http://boyles.sdsmt.edu/geniebot/genie.htm Sponsored by PWISTA.com

  42. Sponsored by PWISTA.com

  43. Reactions Based on Reduction Potentials EMF Potential • Reduction and Oxidation • Single replacement Sponsored by PWISTA.com

  44. Cation Replacement • There are two types of single replacement reactions, in one, a metal or hydrogen replaces a positive ion • M0 + A+B- M+B- + A0 Sponsored by PWISTA.com

  45. Sponsored by PWISTA.com

  46. Replacement of Hydrogen • Reaction of Magnesium and Different Concentrations of Acids • Website: http://boyles.sdsmt.edu/kinetic/mercadokinetics.htm • Hydrochloric Acid(g) + Magnesium(s)  Magnesium(II)Chloride(aq) + Hydrogen(g) • 2HCl(g) + Mg(s)  MgCl2(aq) + H2(g) • Small piece of sodium metal is added to distilled water • Website: http://boyles.sdsmt.edu/sodwat/reaction_of_sodium_and_water.htm • Sodium(s) + Water(l)  Sodium Hydroxide(aq) + Hydrogen(g) • 2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g) Sponsored by PWISTA.com

  47. ) Reaction of Potassium and Water • Website: http://www.chem.shef.ac.uk/webelements-moov/K_H2O.mov • Potassium(s) + Water(l)  Potassium Hydroxide(aq) + Hydrogen(g) • 2K(s) + 2H2O  2KOH + H2(g) • A strip of zinc is added to a solution of 6.0-molar hydrobromic acid • Group I with water video • http://video.google.com/videoplay?docid=-2134266654801392897&q=rubidium+water Sponsored by PWISTA.com

  48. Cation Replacement • Reaction of Zinc and Tin (II) Chloride • Website: http://www.chemtopics.com/lectures/unit02/lecture1/displace.htm • Zinc(s) + Tin (II) Chloride(aq)  Tin(s) + Zinc (II) Chloride(aq) • Zn(s) + SnCl2(aq)  Sn(s) + ZnCl2(aq) Sponsored by PWISTA.com

  49. Thermite Reaction • 2Al(s) + Fe2O3 (s)  Al2O3 (s) + 2Fe(l) • http://boyles.sdsmt.edu/thermite/therm.htm • http://www2.chemie.uni-erlangen.de/education/medprak/videos/thermit_v.mpg Sponsored by PWISTA.com

  50. A solution of copper(II) sulfate is spilled onto a sheet of freshly polished aluminum metal. • Bar of strontium metal is immersed in a 1.0 M copper (II) nitrate solution. • A piece of copper wire is placed in a solution of silver nitrate • A small piece of calcium metal is added to hot distilled water • A solution of tin(II) nitrate is added to a solution of silver nitrate Sponsored by PWISTA.com

More Related