Writing AP Equations

1. Writing AP Equations

2. Warm - Up • Write the complete electronic configuration of the Fe atom in the ground state. Would you expect the atom to be paramagnetic or diamagnetic? (2000) • Describe the energy change when an electron in a H atom is promoted from n=1 to n=3. Explain the terms GROUND state and EXCITED state in this context. (1999) • Consider the element with atomic number 87. Write the valence shell electron configuration of this element. (2006) • Give a possible set of quantum numbers for EACH electron in the valence shell of the Aluminum atom in its ground state. (1980)

3. Warm – Up Solutions • Fe – ground state, para or diamagnetic? element or metal ion? 1s2 2s22p6 3s23p6 4s23d6 Unpaired electrons = paramagnetic

4. Warm – Up Solutions • Energy is absorbed and the electron is promoted from its ground state (the lowest energy state that the electron is normally found) to an excited state (a state where electrons are in higher energy states than would otherwise normally be expected). n = 1 (ground) to n = 3 (excited)

5. Warm – Up Solutions • Atomic # 87 What is the principle quantum # of valence shell? What type of orbital? 7s1

6. Warm – Up Solutions Where is Al? What are the valence electrons? 3s2 3p1 n = 3 s subshell electrons = l = 0 p subshell electrons = l = 1 For l = 0, ml = 0 For l = 1, ml = -1,0,1 ms = ½ or - ½ Find addresses for EACH electron 3, 0, 0, ½ ; 3, 0, 0, - ½ ; 3, 1, -1, ½

7. Writing AP Equations AP equation sets are found in the free-response section of the AP test. You are given 3 equations. The equations are of mixed types. The section is worth 15 points and is 15 % of the free response grade. Free response is 55% of the total AP test grade. First classify the type of reaction. Practice these!!! Speed and accuracy!

8. Types of Reactions • 1. Metathesis (double replacement) • 2. Single replacement • 3. Combustion • 4. Acid/base neutralization • 5. Combination • 6. Decomposition • 7. Reactions of anhydrides • 8. Organic • 9. Non-trivial redox • 10. Complex ion formation or decomposition • 11. Lewis acid/base (adduct formation)

9. Categories of Chemical Compounds • Acids - 7 Strong acids: HCl, HBr, HI, HNO3, H2SO4, HClO3, HClO4 to KNOW…all others dissolve but only partially dissociate!! • Bases – Strong bases: Group I and II hydroxides. • Metal oxides -binary compounds of a metal and oxygen (MgO, K2O) • Non-metal oxides - binary compounds of a non-metal and oxygen (NO, CO2) • Salts (compounds of metals that are NEITHER bases NOR oxides: see solubility rules!) • Other (most compounds belong here!!!!!)

10. Soluble Salts (with exceptions) S2- NH4+ Nitrate Acetate

11. Water • Consider water as HOH (H+, OH-) • Water is a good solvent because the molecules are polar. • The oxygen atoms have a partial negative charge. • The hydrogen atoms have a partial positive charge. • The angle is 105°

12. H H H H O O O H H H H O O H H O O H H H H H H O H O H How Ionic solids dissolve Click here for Animation

13. Writing Net Ionic Equations • All reactions will work, they never give you a reactions that doesn’t proceed to products. • Break up any IONIC compounds (salts, strong acids, strong bases…) • Covalent compounds, weak electrolytes, weak acids and bases, solids, pure liquids, and gases are NOT broken into ions! • Suspensions are NOT broken into ions.

14. Metathesis (Double Replacement) Two compounds react to form two new compounds. No changes in oxidation numbers occur. All double replacement reactions must have a "driving force" that removes a pair of ions from solution. HCl + NaOH → NaCl + HOH AgNO3+ NaCl → AgCl + NaNO3

15. Metathesis Products • Precipitate : insoluble substance formed by the reaction of two aqueous substances. Two ions bond together so strongly that water can not pull them apart. i.e. Solutions of silver nitrate and lithium bromide are mixed • Gas : Gases may form directly in a double replacement reaction or can form from the decomposition of a product such as H2CO3 or H2SO3. i.e. Excess hydrochloric acid solution is added to a solution of potassium sulfite • Molecular substance: When a molecular substance such as water or acetic acid is formed, ions are removed from solution and the reaction "works". i.e. Dilute solutions of lithium hydroxide and hydrobromic acid are mixed

16. Practice Problems Sodium hydroxide is mixed with phosphoric acid. Hydrogen sulfide is bubbled through a solution of silver nitrate. An excess of sodium hydroxide solution is added to a solution of magnesium nitrate. Dilute sulfuric acid is added to a solution of barium acetate.

17. Single Replacement (displacement) Reaction where one element displaces another in a compound. One element is oxidized and another is reduced. (Trivial redox) A + BC  B + AC The more easily oxidized metal replaces the less easily oxidized metal. The metal with the most negative reduction potential will be the most active. Each halogen will displace less electronegative (heavier) halogens from their binary salts (F replaces Cl). Remember there are no “no reactions”!!!

18. Most Active Metals on Top! Reaction of Na+ and K+ with water…

19. Special Cases • Non-aqueous: gas over hot metal oxides – no net ionics…why? • Weak acid/bases replaced by stronger acids/bases. What indicates completion? • NH4Cl + NaOH → NH3+ NaCl + H2O [molecular] • Polyprotic acids i.e. H3PO4 • weak polyprotic acids will only reform step-by-step. The extent to which the acid reforms depends on the amount of stronger acid added. • Equal volumes of equimolar solutions of sodium hydrogen phosphate and hydrochloric acid are mixed : HPO42- + H+ → H2PO4- • Equal volumes of 0.10 M sodium hydrogen phosphate and 0.20 M hydrochloric acid are mixed : HPO42- + 2 H+ → H3PO4 • Notice that in the second case there is twice as much H+ available so the reaction goes an additional step.

20. Practice Problems Magnesium turnings are added to a solution of iron(III) chloride Chlorine gas is bubbled into a solution of potassium iodide Zinc metal is added to a solution of copper (II) nitrate Hydrogen gas is passed over hot copper(II) oxide

21. Single and Double Displacement Practice • Manganese(II) nitrate solution is mixed with sodium hydroxide solution • identify the spectator ions in this reaction; explain • Solutions of zinc sulfate and sodium phosphate are mixed • if a wire loop is dipped into the final reaction mixture and placed in a flame, what color will the flame turn? • Sulfur trioxide gas is bubbled into a solution of sodium hydroxide • is the temperature of the mixture likely to increase or decrease? • Dilute solutions of lithium hydroxide and hydrobromic acid are mixed • which of the reactant solutions will feel slippery on the skin? • A solution of ammonia is added to a dilute solution of acetic acid • how does the conductivity of the final reaction mixture compare with that of either reactant? • Calcium metal is added to a dilute solution of hydrochloric acid • give at least one visual observation for this reaction • Liquid bromine is added to a solution of potassium iodide • which substance is the oxidizing agent? • Magnesium turnings are added to a solution of iron(III) chloride • describe a color change that corresponds to the reaction you write • Hydrogen gas is passed over hot iron(III) oxide • which substance is reduced?

22. Combustion - Elements or compounds combine with O2 • Hydrocarbons or alcohols combine with O2 to form CO2 and H2O. • Ammonia (NH3) combines with limited O2 to produce NO and water IF excess O2 to produce NO2 and H2O. • Nonmetallic sulfides combine with oxygen to form oxides and SO2. If you add EXCESS oxygen, you make XO2 gases! Try this! Solid Zn sulfide is heated in excess oxygen

23. Combustion Practice Carbon disulfide vapor is burned in excess O2. Ethanol is burned completely in air. Solid copper(II) sulfide is heated strongly in O2. The hydrocarbon hexane is burned in excess O2

24. Anhydride Reactions • Anhydride – without water. Water is a reactant in these equations. • Nonmetallic oxides (fake acid) plus water yield acids i.e. Carbon dioxide is bubbled into water • Metallic oxides (fake base) plus water yield bases i.e. Solid sodium oxide is added to water

25. Anhydride Reactions • Metal hydride + H2O  metal hydroxide + H2 • Phosphorous halides + H2O  hydrohalic acid + phosphorous containing acid. • RNH3 – amine, organic base CH3NH3 + H2O  OH- + RNH4+

26. Anhydride Practice • Excess water is added to solid calcium hydride • Solid lithium hydride is added to water • Solid dinitrogen pentoxide is added to water • Phosphorus pentachloride solid is added to water • Solid potassium oxide is added to water • Methylamine gas is bubbled into distilled water

27. Addition/Combination Reactions Two or more elements or compounds combine to form a single product • Group IA or IIA metal may combine with a nonmetal to make a salt. • A higher oxidation state of one nonmetal is obtained when reacting with an excess of the other nonmetal. • Two nonmetals may combine to form a molecular compound.

28. Addition Reactions • A metallic oxide plus carbon dioxide yields a metallic carbonate. (Carbon keeps the same oxidation state) •  A metallic oxide plus sulfur dioxide yields a metallic sulfite. (Sulfur keeps the same oxidation state) •  A metallic oxide plus water yields a metallic hydroxide. •  A nonmetallic oxide plus water yields an acid.

29. Addition Reaction Practice • Solid calcium oxide is exposed to a stream of carbon dioxide gas. • Calcium metal is heated strongly in nitrogen gas. • A piece of lithium metal is dropped into a container of nitrogen gas • Sulfur dioxide gas is passed over solid calcium oxide

30. Acid/Base Neutralizations • Acids react with bases to produce salts and water. One mole of hydrogen ions react with one mole of hydroxide ions to produce one mole of water. Watch out for information about quantities of each reactant! Remember which acids are strong (ionize completely) and which are weak (write as molecule).

31. Complex Ion Reactions • Complex ion- the combination of a central metal ion and its ligands • Ligand- group bonded to a metal ion • Coordination compound- a neutral compound containing complex ions [Co(NH3)6]Cl3(NH3 is the ligand, [Co(NH3)6]3+is the complex ion)

32. Complex ion Name Formed from: • [Al(OH)4]- tetrahydroxoaluminate ion (Al or Al(OH)3 or Al3++ OH-) •  [Ag(NH3)2]+ diamminesilver(I) ion (Ag+ + NH3) •  [Zn(OH)4] 2- tetrahydroxozincate ion (Zn(OH)2 + OH-) •  [Zn(NH3)4] 2+ tetramminezinc ion (Zn2+ + NH3) •  [Cu(NH3)4]2+ tetramminecopper(II) ion (Cu2+ + NH3) •  [Cd(NH3)4] 2+ tetramminecadmium(II) ion (Cd2++ NH3) •  [FeSCN] 2+ thiocyanoiron(III) ion (Fe3+ + SCN-) •  [Ag(CN)2]- dicyanoargentate(I) ion (Ag+ and CN-) Adding an acid to a complex ion will break it up. If HCl is added to a silver Complex, AgCl(s) is formed.  If an acid is added to an ammonia complex, NH4+ is formed.

33. Types of Complex Ion • Complexation of a soluble salt • Complexation of an insoluble salt • Destruction of a complex by acid/base neutralization

34. Complex Ion Practice • 1. Concentrated (15M) ammonia solution is added in excess to a solution of copper(II) nitrate. • 2. An excess of nitric acid solution is added to a solution of tetraaminecopper(II) sulfate. • 3. Dilute hydrochloric acid is added to a solution of diamminesilver(I) nitrate.

35. Oxidation Reduction Reactions • Redox reactions involve the transfer of electrons, and the oxidation numbers of at least two elements must change. • One charge goes up and the other goes down • Polyatomics decompose to gases • Go to metals first • Never include Group I ion (unless it’s a solid) or NO3- and unless it’s HNO3 metal

36. Stuff to Know Common oxidizing agents Products formed MnO4- in acidic solution Mn2+ MnO2 in acidic solution Mn2+ MnO4- in neutral or basic solution MnO2(s) Cr2O72- in acidic solution Cr3+ HNO3, concentrated NO2 HNO3, dilute NO H2SO4, hot, concentrated SO2

37. Redox Practice Problems • A solution of tin(II) chloride is added to an acidified solution of potassium permanganate. • A solution of tin(II) sulfate is added to a solution of iron(III) sulfate • Hydrogen peroxide solution is added to a solution of iron(II) sulfate • A piece of iron is added to a solution of iron(III) sulfate .