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Writing Reaction Equations for the A.P. Chemistry Exam

Writing Reaction Equations for the A.P. Chemistry Exam. Common Chemicals List: NH 3 – ammonia ( window cleaner ) HC 2 H 3 O 2 – acetic acid or ethanoic acid ( vinegar ) C 6 H 12 O 6 – glucose (blood sugar; simple sugar) C 12 H 22 O 11 – sucrose ( table sugar )

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Writing Reaction Equations for the A.P. Chemistry Exam

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  1. Writing Reaction Equations for the A.P. Chemistry Exam

  2. Common Chemicals List: • NH3 – ammonia (window cleaner) • HC2H3O2 – acetic acid or ethanoic acid (vinegar) • C6H12O6 – glucose (blood sugar; simple sugar) • C12H22O11 – sucrose (table sugar) • C2H4(OH)2 – ethylene glycol (antifreeze) • I2 in alcohol – tincture of iodine (alcohol solution of iodine found in small bottles in medicine cabinet) • H2O2 – hydrogen peroxide (peroxide…3% solution found in brown bottles in medicine cabinet) • NaClO – sodium hypochlorite (laundrybleach) • O3 – triatomic oxygen (ozone)

  3. Common Chemicals List: • NaHCO3 – sodium bicarbonate (baking soda) • Na2CO3 – sodium carbonate (washing soda) • CH3OH – methanol (wood alcohol) • C2H5OH – ethanol (grain alcohol) • H3C6H5O6 – ascorbic acid (vitamin C) • CaO – calcium oxide (lime) • C10H8 – napthalene (moth balls…two fused benzene rings) • C6H4Cl2 – paradichlorobenzene (also moth balls) • SiO2 – silicon dioxide (amorphous-glass; crystalline- quartz; aka sand) • C6H5CH3 – toluene, methylbenzene or phenylmethane (paint thinner, mineral spirits) Three Letter Compounds: • TBA tertiary butyl alcohol • MEK methyl ethyl ketone • TTE trichloro trifluoro ethane • KHP potassium hydrogen phthalate

  4. Writing Reaction Equations for the A.P. Chemistry Exam · Putting together two solutions 1. PPT’s – Be familiar with the general solubility rules 2. Complex Ion Formation – Go over complexes formed in Qual. Labs. 3. Bronsted-Lowrey Acid/Base - Be familiar with strong and weak acids and bases

  5. Writing Reaction Equations for the A.P. Chemistry Exam If you see what would be the products in a decomposition reaction as the reactants in a synthesis reaction, then view the reaction as a “reverse” decomposition · Decompositions 1. Carbonates - When carbonates decompose they break down into metal oxides and carbon dioxide 2. Bicarbonates - When bicarbonates decompose they break down into metal carbonates, carbon dioxide water 3. Chlorates - When chlorates decompose they break down into metal chlorides and oxygen. 4. Hydroxides - When hydroxides decompose they break down into metal oxides and water. 5. Binary Compounds - Break down into their elements except for... 6. Peroxides - Break down into the metal oxide and oxygen.

  6. Writing Reaction Equations for the A.P. Chemistry Exam · Acidic or Basic Anhydrides in water 1. Acidic - Covalently bonded oxides (nonmetals with oxygen) combine with water to make acids. 2. Basic - Ionically bonded oxides (metals with oxygen) combine with water to make bases.

  7. Writing Reaction Equations for the A.P. Chemistry Exam · REDOX reactions 1. MnO4- and Cr2O72- are typically used as oxidizers. (MnO4- typically is reduced to Mn2+, Cr2O72- is typically reduced to Cr3+). 2. Identify the half reactions…go through the steps of balancing to identify all species present (i.e. H+, OH-, H2O). 3. Other substances to know about: CO (strong reducing agent); O22- (strong oxidizing agent); HNO3 and H2SO4 are oxidizing acids

  8. Writing Reaction Equations for the A.P. Chemistry Exam · Remember the reaction categories from the Honors Chem. course 1. Synthesis - one product (look for reverse decompositions) 2. Single Replacement…remember activities 3. Double Replacement 4. Combustion - hydrocarbon fuels react with oxygen to make carbon dioxide and water. 5. A Carbonate plus an Acid - always makes a salt, carbon dioxide and water

  9. Writing Reaction Equations for the A.P. Chemistry Exam · Make sure, after you are done, that you have considered: 1. The major species present (i.e. weak acids should be shown as molecules whereas strong acids should be shown as ions). 2. Only net ionic equations should be shown… don’t include spectator ions. 3. Don’t worry about showing phases…you don’t need to show them. • Assume solutions are aqueous unless otherwise noted 5. Balance all equations w/ the smallest whole #’s

  10. Practice I 1.) Solutions of sodium iodide and lead nitrate are mixed. PPT 2NaI(aq) + Pb(NO3)2(aq) --> 2NaNO3(aq) + PbI2(s) 2Na+ + 2I- + Pb2+ + 2NO3- --> 2Na+ + 2NO3- + PbI2 2I- + Pb2+ --> PbI2 The reverse reaction would likely be favored as raising the temperature generally increases the solubility of solids in liquids.

  11. Practice I 2.) A solution of hydrogen peroxide is heated. peroxide decomposition 2H2O2 --> 2H2O + O2 The oxidation number of the oxygen in the reactants is -1; the oxidation number of the oxygen in the products is -2 and 0. This is a disproportionation reaction.

  12. Practice I 3.) Hydrogen sulfide gas is bubbled through a solution of potassium hydroxide. B-L acid/base…also D.R. H2S(g) + KOH(aq) --> H2O(l) + KHS(aq) H2S + K+ + OH- --> H2O + K+ +HS- H2S + OH- --> H2O + HS- The color of the litmus would be blue. The product bisulfide, HS-, is a base stronger than water. Litmus is blue in the presence of a base.

  13. Practice I 4.) Solid dinitrogen pentoxide is added to water acid anhydride N2O5 + H2O -->2HNO3 N2O5 + H2O --> 2H+ + 2NO3- Less than 7. Dinitrogen pentoxide is an acid anhydride producing hydrogen ions in water decreasing the pH.

  14. Practice I 5.) A piece of solid aluminum is heated strongly in oxygen. synthesis, redox 4Al + 3O2 --> 2Al2O3 The aluminum would be the limiting reactant. One mole of aluminum would require 0.75 moles of oxygen. If equal numbers of moles of reactants were added, there would be extra oxygen.

  15. Practice I 6.) A strip of copper metal is added to a concentrated solution of sulfuric acid redox Cu + 3H+ + HSO4- --> Cu2+ + 2H2O + SO2 The reddish brown copper metal would get used up and eventually go away. The solution would become more and more blue as the Cu2+ ion concentration increases.

  16. Practice II 1.) Calcium oxide powder is added to distilled water. basic anhydride CaO + H2O --> Ca(OH)2 or CaO + H2O --> Ca2+ + 2OH- This solution could be used to test for the gas carbon dioxide. The name of this solution is limewater

  17. Practice II 2.) Liquid bromine is shaken with a 0.5 M sodium iodide solution. S.R. / redox Br2(l) + 2NaI(aq) --> 2NaBr (aq) + I2(aq) Br2 + 2Na+ +2 I- --> 2Na+ + 2Br- + I2 Br2 + 2I- --> 2Br- + I2 The reducing agent in this reaction is the sodium iodide solution (or just the iodide ion). The iodide is being oxidized from a state of -1 to 0. It is providing electrons for the bromine to aid aiding in its reduction.

  18. Practice II 3.) Solid lead (II) carbonate is added to a 0.5 M solution of sulfuric acid. carbonate plus an acid PbCO3(s)+ H2SO4(aq) --> PbSO4(s) + H2O(l) + CO2(g) PbCO3+ H+ + HSO4- --> PbSO4 + H2O + CO2 The mass of the material in the test tube in which this reaction may occur would be less than before the reaction as the gas produced would escape and not be accounted for.

  19. Practice III 1.) A mixture of powdered iron (III) oxide and powdered aluminum metal is heated strongly S.R. (thermite reaction!!) Fe2O3 + 2Al --> Al2O3 + 2Fe A negative value for the change in enthalpy means that the reaction is exothermic and energy is released as the reaction occurs. Therefore the energy needed to break the bonds of the reactants must be less than the energy released as the bonds in the product are made.

  20. Practice III 2.) Methylamine gas is bubbled into distilled water. B-L weak acid/base CH3NH2 + H2O --> OH- +CH3NH3+ Phenolphthalein is pink is the presence of a base. Methylamine produces hydroxide ions in solution as it reacts with water and behaves like a base. Therefore, a drop of phenolphthalein into this sol’n would turn pink.

  21. Practice III 3.) Carbon dioxide gas is passed over hot, sodium oxide. (synthesis, seen as a reverse decomp.) CO2 + Na2O --> Na2CO3 The sign on DS° would be negative because the reactants contain a gas and a solid while the products contain only a solid. Gases are more entropic than solids and so the entropy of the system in decreasing.

  22. Practice IV 1.) A small piece of calcium metal is added to hot distilled water. S.R., redox Ca + 2H2O --> Ca(OH)2 + H2 or Ca + 2H2O --> Ca2+ + 2OH- + H2 2.) Butanol is burned in air. combustion C4H9OH + 6O2 --> 5H2O + 4CO2

  23. Practice IV 3.) Excess concentrated ammonia solution is added to a solution of nickel (II) sulfate. complex ion formation 4NH3(aq) + NiSO4(aq) --> Ni(NH3)42+(aq) + SO42-(aq) 4NH3 + Ni2+ + SO42- --> Ni(NH3)42+ + SO42- 4NH3 + Ni2+ --> Ni(NH3)42+ 4.) A solution of copper (II) chloride is added to a solution of sodium sulfide. PPT CuCl2(aq)+ Na2S(aq) --> CuS(s) + 2NaCl(aq) Cu2+ + 2Cl- + 2Na+ + S2- --> CuS+ 2Na+ + 2Cl- Cu2+ + S2- --> CuS

  24. Practice IV 5.) A solution of tin (II) nitrate is added to a solution of silver nitrate. redox Sn2+ + 2Ag+ --> Sn4+ + 2Ag 6.) Carbon monoxide gas is passed over hot iron (III) oxide. redox 3CO + Fe2O3 --> 3CO2 + 2Fe

  25. Bonus #1 Calcium chloride is heated strongly in the presence of oxygen. synthesis…(can be seen a reverse decomposition) CaCl2 + 3O2 --> Ca(ClO3)2

  26. Bonus#2 Acetic acid solution is combined with a sodium hydroxide solution acid/base HC2H3O2+ OH- --> H2O + C2H3O2-

  27. Bonus#3 A solution of aluminum nitrate in an excess of sodium hydroxide complex ion formation Al3++ 4OH- --> Al(OH)4-

  28. Bonus#4 A solution of silver nitrate and a solution of magnesium chloride are combined PPT Ag++ Cl- --> AgCl

  29. Bonus#5 Magnesium oxide is combined with water basic anhydride MgO+ H2O -->Mg2+ + 2OH- or MgO + H2O --> Mg(OH)2

  30. Bonus#6 Strontium hydroxide is heated over a flame. decomposition Sr(OH)2 --> SrO + H2O

  31. Bonus#7 A solution of sodium dichromate is added to an acidified solution of nickel (II) nitrate Redox (in acid environment) 14H++ Cr2O72- + 6Ni2+ --> 6Ni3+ + 2Cr3+ + 7H2O

  32. Bonus#8 A solution of silver nitrate is poured over a coil of copper wire. S.R. or redox 2Ag+ + Cu --> Cu2+ + 2Ag

  33. Bonus#9 Excess concentrated ammonia solution is added to a solution of cobalt (II) nitrate Complex ion formation 4NH3 + Co2+ --> Co(NH3)42+

  34. Bonus#10 Phosphorous (V) oxide is placed in water. acidic anhydride P2O5 + 3H2O --> 2H3PO4

  35. A solution of potassium permanganate is added to an acidic solution of ferrous nitrate Bonus#11 redox in acid environment 8H+ + MnO4-+ 5Fe2+ --> 5Fe3+ + Mn2+ + 4H2O

  36. Bonus#12 A dilute solution of sodium hydroxide is added to a dilute solution of hydrogen phosphate. acid / base OH-+ H3PO4 --> H2O + H2PO4-

  37. Bonus#13 Propanone is burned in air combustion CH3COCH3 + 4O2 --> 3CO2 + 3H2O or C3H6O+ 4O2 --> 3CO2 + 3H2O

  38. Bonus #14 Solid zinc carbonate is added to 1.0 M sulfuric acid carbonate and an acid ZnCO3+ H+ + HSO4- --> Zn2+ + SO42- + CO2 + H2O

  39. Bonus#15 Calcium is burned in air Synthesis or combustion (but not a hydrocarbon fuel) 2Ca+ O2 --> 2CaO

  40. Bonus#16 Hydrogen iodide solution reacts with a solution of lithium hydroxide. strong acid/strong base H++ OH- --> H2O

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