Unit 5: Chemical Equations and Reactions & Stoichiometry

Transcription

1 pg. 10 Unit 5: Chemical Equations and Reactions & Stoichiometry Chapter 8: Chemical Equations and Reactions 8.1: Describing Chemical Reactions Selected Chemistry Assignment Answers (Section Review on pg. 266) 5. C 3 H 8 + O 2 CO 2 + H 2 O 6. C 3 H 8 (g) + O 2 (g) CO 2 (g) + H 2 O (l) 9. silicon tetrachloride + magnesium silicon + magnesium chloride ; SiCl 4 (g) + Mg (s) Si (s) + MgCl 2 (s) 10. magnesium + oxygen magnesium oxide ; Mg (s) + O 2 (g) MgO (s) 8.2: Balancing Chemical Equations (Practice on pg. 269) 1. P O 2 2 P 2 O 5 2. C 3 H O 2 3 CO H 2 O 3. Ca 2 Si + 4 Cl 2 2 CaCl 2 + SiCl Si + CO 2 SiC + SiO 2 (Practice on pg. 271) 1. 2 C 2 H O 2 4 CO H 2 O 2. 2 Fe(OH) 2 + H 2 O 2 2 Fe(OH) FeS Cl 2 2 FeCl S 2 Cl 2 (Practice on pg. 273) 1. HgCl AgNO 3 Hg(NO 3 ) AgCl 2. 2 Al + 3 Hg(CH 3 COO) 2 2 Al(CH 3 COO) Hg 3. 3 Ca(OH) H 3 PO 4 Ca 3 (PO 4 ) H 2 O (Section Review on pg. 274) 4. (a) potassium chlorate potassium chloride + oxygen ; KClO 3 KCl + O 2 ; 2 KClO 3 2 KCl + 3 O 2 (b) silver + sulfur silver sulfide ; Ag + S 8 Ag 2 S ; 16 Ag + S 8 8 Ag 2 S (c) sodium hydrogen carbonate sodium carbonate + carbon dioxide + water ; NaHCO 3 Na 2 CO 3 + CO 2 + H 2 O ; 2 NaHCO 3 Na 2 CO 3 + CO 2 + H 2 O 5. (a) 2 ZnS + 3 O 2 2 ZnO + 2 SO 2 (b) Fe 2 O CO 2 Fe + 3 CO 2 (c) 3 AgNO 3 + AlCl 3 3 AgCl + Al(NO 3 ) 3 (d) Ni(ClO 3 ) 2 NiCl O 2 6. (a) (NH 4 ) 2 Cr 2 O 7 Cr 2 O 3 + N H 2 O (b) 2 NH CuO N Cu + 3 H 2 O (c) Na 2 SiF Na Si + 6 NaF (d) 2 C 4 H O 2 8 CO H 2 O 7. P O 2 2 P 2 O 3 (Given only 4 atoms of phosphorus or 1 molecule of P 4, even if there are more than 3 molecules of oxygen, there can only be two molecules of P 2 O 3. This is because the number of phosphorus atoms limits how many P 2 O 3 molecules can form.) 9. 2 H 2 + O 2 2 H 2 O Reactants: 2(2.02 amu) + 1(32.00 amu) = amu ; Product: 2 (18.02 amu) = amu 10. The correct equation should be 2 Fe (s) + 3 Cl 2 (g) 2 FeCl 3 (s) ; Chlorine is a diatomic element (Cl 2 ). 8.3: Classifying Chemical Reactions (Practice on pg. 279) 1. (Hydrocarbon Combustion) 2 C 4 H O 2 8 CO H 2 O 2. (Synthesis) H 2 O + CaO Ca(OH) 2 3. (Synthesis) 4 Li + O 2 2 Li 2 O (Practice on pg. 282) 1. 2 Al + 3 Zn(NO 3 ) 2 2 Al(NO 3 ) Zn 2. 2 Na + 2 H 2 O 2 NaOH + H 2 3. No reaction

2 Selected Chemistry Assignment Answers pg. 11 (Section Review on pg. 285) 4. water and carbon dioxide 7. a solid precipitate, a gas, or a molecular compound, such as water 8. (a) (single displacement) Cl 2 (g) + 2 NaBr (aq) 2 NaCl (aq) + Br 2 (l) (b) (synthesis) CaO (s) + H 2 O (l) Ca(OH) 2 (aq) (c) (decomposition) Ca(ClO 3 ) 2 (s) CaCl 2 (s) + 3 O 2 (g) (d) (double displacement) 2 AgNO 3 (aq) + K 2 SO 4 (aq) Ag 2 SO 4 (s) + 2 KNO 3 (aq) (e) (single displacement) Zn (s) + CuBr 2 (aq) ZnBr 2 (aq) + Cu (s) (f) (hydrocarbon combustion) 2 C 8 H 18 (l) + 25 O 2 (g) 16 CO 2 (g) + 18 H 2 O (g) 9. (a) no reaction (b) (single displacement) Mg (s) + Cu(NO 3 ) 2 (aq) Cu (s) + Mg(NO 3 ) 2 (aq) (c) (synthesis) 4 Al (s) + 3 O 2 (g) 2 Al 2 O 3 (s) (d) (double displacement) H 2 SO 4 (aq) + 2 KOH (aq) K 2 SO 4 (aq) + 2 HOH (l) 10. (a) (decomposition) 2 HgO 2 Hg + O 2 (b) (hydrocarbon combustion) 2 C 3 H 7 OH + 10 O 2 6 CO H 2 O (c) (single displacement) Zn + CuSO 4 Cu + ZnSO 4 (d) (double displacement) BaCl 2 + Na 2 SO 4 2 NaCl + BaSO 4 (e) (synthesis) Zn + F 2 ZnF 2 (f) (hydrocarbon combustion) 2 C 5 H O 2 10 CO H 2 O 14. Yes, copper is higher than silver on the activity series and will replace the silver in silver nitrate. 8.4: Writing Net-Ionic Equations (Section Review on pg. 289) 3. No, NaCl (aq) is an ionic solution and should be written as Na + and Cl. Since both ions are shown on both sides of the equation, they are all spectator ions. 4. Mg 2+ and NO 3 6. (a) Br 2 (l) + 2 Na + (aq) + 2 I (aq) 2 Na + (aq) + 2 Br (aq) + I 2 (s) (b) Ca 2+ (aq) + 2 OH (aq) + 2 H + (aq) + 2 Cl (aq) Ca 2+ (aq) + 2 Cl (aq) + 2 H 2 O (l) (c) Mg (s) + 2 Ag + (aq) + 2 NO 3 (aq) 2 Ag (s) + Mg 2+ (aq) + 2 NO 3 (aq) (d) Ag + (aq) + NO 3 (aq) + K + (aq) + Br (aq) AgBr (s) + K + (aq) + NO 3 (aq) (e) Ni (s) + Pb 2+ (aq) + 2 NO 3 (aq) Ni 2+ (aq) + 2 NO 3 (aq) + Pb (s) (f) Ca (s) + 2 H 2 O (l) Ca 2+ (aq) + 2 OH (aq) + H 2 (g) 7. (a) (spectator ion = Na + ) Br 2 (l) + 2 I (aq) 2 Br (aq) + I 2 (s) (b) (spectator ions = Ca 2+ and Cl ) OH (aq) + H + (aq) H 2 O (l) (c) (spectator ion = NO 3 ) Mg (s) + 2 Ag + (aq) 2 Ag (s) + Mg 2+ (aq) (d) (spectator ions = K + and NO 3 ) Ag + (aq) + Br (aq) AgBr (s) (e) (spectator ion = NO 3 ) Ni (s) + Pb 2+ (aq) Ni 2+ (aq) + Pb (s) (f) (no spectator ions) Ca (s) + 2 H 2 O (l) Ca 2+ (aq) + 2 OH (aq) + H 2 (g) 8. (a) (products = Au (s) and AgCl (s)) Au 3+ (aq) + 3 Cl (aq) + 3 Ag (s) Au (s) + 3 AgCl (s) (b) (products = AgCl (s) and Ca(NO 3 ) 2 (aq) ) 2 Ag + (aq) + 2 NO 3 (aq) + Ca 2+ (aq) + 2 Cl (aq) 2 AgCl (s) + Ca NO 3 (aq) (c) (products = Ni (s) and Al 2 (SO 4 ) 3 (aq) ) 2 Al (s) + 3 Ni 2+ 2 (aq) + 3 SO 4 (aq) 3 Ni (s) + 2 Al 3+ 2 (aq) + 3 SO 4 (aq) (d) (products = NaOH (aq) and H 2 (g) ) 2 Na (s) + 2 HOH (l) 2 Na + (aq) + 2 OH (aq) + H 2 (g) (e) (products = AgCl (s) and NaNO 3 (aq) ) Ag + (aq) + Cl (aq) + Na + (aq) + NO 3 (aq) AgCl (s) + Na + (aq) + NO 3 (aq)

3 pg. 12 Selected Chemistry Assignment Answers 9. (a) (no spectator ions) Au 3+ (aq) + 3 Cl (aq) + 3 Ag (s) Au (s) + 3 AgCl (s) (b) (spectator ions = Ca 2+ and NO 3 ) 2 Ag + (aq) + 2 Cl (aq) 2 AgCl (s) (c) (spectator ion = SO 2 4 ) 2 Al (s) + 3 Ni 2+ (aq) 3 Ni (s) + 2 Al 3+ (aq) (d) (no spectator ions) 2 Na (s) + 2 HOH (l) 2 Na + (aq) + 2 OH (aq) + H 2 (g) (e) (spectator ion = Na + and NO 3 ) Ag + (aq) + Cl (aq) AgCl (s) 10. (a) 2 Ag + (aq) + 2 NO 3 (aq) + 2 Na + 2 (aq) + SO 4 (aq) 2 Na + (aq) + 2 NO 3 (aq) + Ag 2 SO 4 (s) (b) 2 Al (s) + 3 Ni 2+ (aq) + 6 I (aq) 3 Ni (s) + 2 Al 3+ (aq) + 6 I (aq) (c) 2 K + 2 (aq) + SO 4 (aq) + Ca 2+ (aq) + 2 Cl (aq) CaSO 4 (s) + 2 K + (aq) + 2 Cl (aq) (d) Mg (s) + Cu 2+ (aq) + 2 Br (aq) Cu (s) + Mg 2+ (aq) + 2 Br (aq) (e) Pb 2+ (aq) + 2 NO 3 (aq) + 2 Na + (aq) + 2 Cl (aq) PbCl 2 (s) + 2 Na + (aq) + 2 NO 3 (aq) 11. (a) (spectator ions = NO 3 and Na + ) 2 Ag + 2 (aq) + SO 4 (aq) Ag 2 SO 4 (s) (b) (spectator ion = I ) 2 Al (s) + 3 Ni 2+ (aq) 3 Ni (s) + 2 Al 3+ (aq) (c) (spectator ions = K + and Cl ) Ca 2+ 2 (aq) + SO 4 (aq) CaSO 4 (s) (d) (spectator ion = Br ) Mg (s) + Cu 2+ (aq) Cu (s) + Mg 2+ (aq) (e) (spectator ions = NO 3 and Na + ) Pb 2+ (aq) + 2 Cl (aq) PbCl 2 (s) 12. All potassium compounds are soluble. Hence K + will always be a spectator ion in double displacement reactions. 15. If a double-displacement reaction has four spectator ions, then both reactants and products are soluble. All four ions are spectator ions and no reaction (as well as no observations of chemical change) will happen. (Chapter Review on pg. 293 to 295) 26. (a) H 2 + Cl 2 2 HCl (b) 2 Al + Fe 2 O 3 2 Fe + Al 2 O 3 (c) Ba(ClO 3 ) 2 BaCl O 2 (d) omit 27. (a) Fe 2 O Mg 3 MgO + 2 Fe (b) 3 NO 2 + H 2 O 2 HNO 3 + NO (c) SiCl H 2 O SiO HCl 28. (a) 4 Fe + 3 O 2 2 Fe 2 O 3 (b) 2 H 2 O 2 2 H 2 O + O 2 (c) 2 C 8 H O 2 16 CO H 2 O (d) 2 Al + 3 F 2 2 AlF (a) 2 C 3 H 7 OH + 9 O 2 6 CO H 2 O (b) 2 Al + 3 Fe(NO 3 ) 2 2 Al(NO 3 ) Fe (c) 2 PbO 2 2 PbO + O (a) Zn + Pb(NO 3 ) 2 Pb + Zn(NO 3 ) 2 (b) H 2 OOCCOO + 2 NaOH Na 2 OOCCOO + 2 HOH (c) 2 Al + 3 CuSO 4 Al 2 (SO 4 ) + 3 Cu 31. (a) CuSO 4 + (NH 4 ) 2 S CuS + (NH 4 ) 2 SO 4 (b) 2 HNO 3 + Ba(OH) 2 2 HOH + Ba(NO 3 ) 2 (c) 3 BaCl H 3 PO 4 Ba 3 (PO 4 ) HCl 32. (a) 2 Zn + O 2 2 ZnO (b) F 2 + Mg MgF 2 (c) Cl K 2 KCl (d) H 2 + I 2 2 HI 33. (a) 2 HgO 2 Hg + O 2 (b) 2 H 2 O 2 H 2 + O 2 (c) 2 AgCl 2 Ag + Cl (a) 2 C 3 H O 2 6 CO H 2 O (b) C 5 H O 2 5 CO H 2 O (c) 2 CH 3 OH + 3 O 2 2 CO H 2 O (d) C 12 H 22 O O 2 12 CO H 2 O 35. (a) (hydrocarbon combustion) C 3 H O 2 3 CO H 2 O (b) (decomposition) Na 2 CO 3 Na 2 O + CO 2 (d) (combustion) C 2 H 5 OH + 3 O 2 2 CO H 2 O 36. (a) Mg (s) + CuCl 2 (aq) MgCl 2 (aq) + Cu (s) (b) Pb(NO 3 ) 2 (aq) + Zn (s) Zn(NO 3 ) 2 (aq) + Pb (s) (c) 2 KI (aq) + Cl 2 (g) 2 KCl (aq) + I 2 (s) (d) no reaction 37. (a) 2 HOH (l) + Ba (s) Ba(OH) 2 (aq) + H 2 (g) (b) 4 Ca (s) + O 2 (g) 2 CaO (s) (c) no reaction

4 Selected Chemistry Assignment Answers pg (a) (combustion) 2 C 2 H O 2 4 CO H 2 O (b) (single displacement) 3 H 2 SO Al Al 2 (SO 4 ) H 2 (c) (synthesis) N Mg Mg 3 N 2 (e) ( double displacement) no reaction 39. (a) (single displacement) 2 HOH + 2 Li 2 LiOH + H 2 (b) (double displacement) AgNO 3 + HCl AgCl (s) + HNO 3 (c) (decomposition) 2 HI H 2 + I (a) (hydrocarbon combustion) C 2 H 5 OH + 3 O 2 2 CO H 2 O (b) (double displacement) HNO 3 + LiOH LiNO 3 + HOH (l) (c) (double displacement) Pb(NO 3 ) 2 + Na 2 CO 3 PbCO 3 (s) + 2 NaNO (a) Total Ionic: H + (aq) + Cl (aq) + Na + (aq) + OH (aq) Na + (aq) + Cl (aq) + HOH (l) Net Ionic: H + (aq) + Cl (aq) H 2 O (l) (b) Total Ionic: Mg (s) + 2 H + (aq) + 2 Cl (aq) Mg 2+ (aq) + 2 Cl (aq) + H 2 (g) Net Ionic: Mg (s) + 2 H + (aq) Mg 2+ (aq) + H 2 (g) (c) Total Ionic: Cd 2+ (aq) + 2 Cl (aq) + 2 Na + 2 (aq) + CO 3 (aq) 2 Na + (aq) + 2 Cl (aq) + CdCO 3 (s) Net Ionic: Cd 2+ 2 (aq) + CO 3 (aq) CdCO 3 (s) 42. (a) Na + and Cl (b) Cl (c) Na + and Cl 43. (a) (products = KCl (aq) and CaCO 3 (s) ) 2 CO 3 (aq) + Ca 2+ (aq) CaCO 3 (s) (b) (products = NaNO 3 (aq) and Ag 2 SO 4 (s) ) 2 SO 4 (aq) + 2 Ag + (aq) Ag 2 SO 4 (s) (c) (products = NH 4 NO 3 (aq) and AgCl (s)) 44. (a) K + and Cl (b) Na + and NO 3 Cl (aq) + Ag + (aq) AgCl (s) (c) NH + 4 and NO 3 (Standardize Test Prep on pg. 298 & 299) 1. D 2. G 3. A 4. Mg (s) + Zn 2+ (aq) Mg 2+ (aq) + Zn (s) 5. Formula equations give only the identity of the reactants and the products but a balanced equation shows equal numbers of atoms of each element on both sides. 6. Fe(NO 3 ) LiOH 3 LiNO 3 + Fe(OH) 3 7. The gas that burns is a different chemical substance than any of the reactants, indicating a chemical reaction. 8. F 9. C 10. H 11. D 12. I Chapter 9: Stoichiometry 9.1: Calculating Quantities in Reactions (Practice on pg. 304) 1. (a) mol O 2 (b) 1.34 mol H 2 O 2. (a) 6.60 mol Al (b) 6.60 mol Fe (c) 3.30 mol Al 2 O 3 (Practice on pg. 307) g Al g Al 2 O g Fe 2 O g Fe (Practice on pg. 309) ml C 3 H L H ml C 5 H ml H 2 (Practice on pg. 311) molecules BrF molecules Br 2 (Section Review on pg. 311) particles 2. the molar mass of the substance; Avogadro s number, 1mol

5 pg. 14 Selected Chemistry Assignment Answers g CO particles, 1mol CO2 1mol 4. (a) 5.48 mol BrCl (b) g BrCl (c) g Br 2 5. (a) 1.42 mol CO 2 (b) 47.2 ml CO 2 7. (a) 2 LiOH + CO 2 Li 2 CO 3 + H 2 O ; 2 NaOH + CO 2 Na 2 CO 3 + H 2 O (b) 524 g NaOH ; 313 g LiOH 9.2: Limiting Reactants and Percentage Yield (Practice on pg. 314) 1. PCl 3 is excess, H 2 O is limiting, theoretical yield = 109 g HCl 2. H 2 O is excess, PCl 3 is limiting, theoretical yield = 59.7 g HCl 3. PCl 3 is excess, H 2 O is limiting, theoretical yield = 101 g HCl (Practice on pg.317) 1. N 2 is limiting, % yield = 85.3% 2. C 2 H 5 OH is limiting, % yield = 80.0% 3. Br 2 is limiting, % yield = 90.9% (Practice on pg. 318) g NH g CH 3 OH g BrCl (Section Review on pg. 319) 6. Theoretical yield = g H 2 ; % yield = 84.4% 7. (a) P 4 O H 2 O 4 H 3 PO 4 (b) g H 3 PO 4 (c) % yield = 91.4% 8. TiCl 4 is limiting; 3.5 mol TiO 2 and 7.0 mol Cl 2 are produced, 1.0 mol O 2 left over g Cu 10. % yield = 93.8% 11. (a) Mg + 2 HOH Mg(OH) 2 + H 2 (b) % yield = 86.8% (c) 55 g Mg(OH) (a) CuO is limiting (b) % yield = 94.3% (c) 15.0 g Cu mol H 2, 10 mol O 2, and 20 mol H 2 O 14. Theoretical yield = 23 g CaO. The actual yield reported is 27 g, which gives a % yield of 120%. The result can be explained by the possibility that there were impurities in the reactant samples, or the measurement of the mass of the reactant is less than its actual mass. In addition, the decomposition reaction might not have reached completion and some of the reactants remained behind. 9.3: Stoichiometry and Cars (Practice on pg. 322) g Na g Fe 2 O g NaHCO 3 4. (a) 168 g NaHCO 3 (b) g HC 2 H 3 O 2 (Practice on pg. 324) cycles; After 3 full cycles, all of the 1.00 ml of isooctane will have reacted ml of isooctane 3. 2 CH 3 OH + 3 O 2 2 CO H 2 O ; L of air (Section Review on pg. 327) g Na 2 O g NaHCO 3 (Chapter Review on pg. 329 to 332) 21. (a) 6.6 mol H 2 (b) 3.36 mol O 2 (c) 8.12 mol H (a) mol H 2 O (b) mol N 2 O 4 (c) mol N 2

6 Selected Chemistry Assignment Answers pg (a) 1.08 mol O 2 (b) 2.62 mol Al 2 O (a) 273 g H 2 O (b) 58.1 g CaC 2 (c) 26.9 g H 2 O 25. (a) 49.0 g O 2 (b) 748 g KClO 3 (c) 12.7 g KCl g Al 2 O (a) 1.68 L O 2 (b) g KClO 3 (c) ml O (a) 113 L O 2 (b) 25 L O (a) molecules NO 2 (b) molecules NO (c) molecules O (a) molecules H 2 (b) atoms Na (c) molecules H (a) O 2 is excess; NO is limiting (b) 4.0 mol NO (a) H 2 O is excess; CaC 2 is limiting (b) 26 g C 2 H 2 (c) 74 g Ca(OH) (a) H 2 is excess; N 2 is limiting (b) 34 g NH 3 (c) 22 g H % yield = 75.6 % 35. % yield = 88.2 % 36. % yield = 72.5% g NaNO g Al kg Fe L CO (a) 84.7 g NaN 3 (b) 43 L N 2 (c) 90 g NaN mol O2 2 mol C8H18 or 25 : g O L O g O 3 ; % yield = 96.4% g CO 2 ; % yield = 88.0% 47. (a) g CO 2 (b) 9.70 ml H 2 O (c) molecules H 2 O L N HNO g CO 2 (Standardize Test Prep on pg. 334 & 335) 1. D 2. I 3. D 4. The limiting reactant is nitrogen dioxide and the excess is water O 3 3 O g O 2 7. H 8. C 9. In general, the products of an explosion are much more stable than the reactants. 10. H 11. The Stoichiometry of the reaction is needed in order to calculate the amount of gas produced. If the wrong amount of reactant is used, the airbag might over-inflate or under-inflate, making it ineffective. 12. A mol