Homework #3 Chapter 4 Types of Chemical Reactions and Solution Stoichiometry

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1 Homework #3 Chapter 4 Types of Chemical Reactions and Solution Stoichiometry 13. Determine the concentrations of the solutions Solution A 4 particles 1.0 L Solution B 6 paticles 4.0 L Solution C 4 particles 2.0 L Solution D 6 particles 2.0L 4.0 particles L 1.5 particles L 2.0 particles L 3.0 particles L Therefore, the order of solution from most to least concentrated is solution A > solution D > solution C > solution B 15. a) Polar solutes will mix with water and nonpolar solutes will not. For polar solutes the water molecules will orientate so that the Hatoms are lined up around the anion and the Oatoms are lined up around the cation. If the solutes are liquids then you will see only see one solution after water has been mixed with a polar solute and two layers when water has been mixed with a nonpolar solute. b) When KF is put into water it will dissociate into K + and F because it is a strong electrolyte. The water molecules will orientate themselves so that the Hatoms in the water are near the F ions and the Oatoms in the water are near the K + ions. When C 6H 12O 6 dissolves in water it will stay as C 6H 12O 6 molecules and not dissociate into atoms/ions because C 6H 12O 6 is a nonelectrolyte. The water molecules will orientate themselves so that the Hatoms in the water are near the partially negative locations in C 6H 12O 6 and the Oatoms in the water are near the partially positive regions of the molecule. c) When RbCl is put into water it will dissociate in Rb + and Cl because it is a strong electrolyte. The water molecules will orientate themselves so that the Hatoms in the water are near the Cl ions and the Oatoms in the water are near the Rb + ions. When AgCl is put into solution it will stay as a solid because it is not soluble in water. d) HNO 3 is a strong acid and will complete dissociate into H + and NO 3. The water molecules will orientate themselves so that the Hatoms in the water are near the NO 3 ions and the Oatoms in the water are near the H + ions. CO is a nonelectrolyte and will not dissociate in water. The water molecules will orientate themselves so that the H atoms in the water are near the O of the CO and the Oatoms in the water are near the C of the CO. 17. Determine the formula and ions of each of the names a) barium nitrate Ba(NO 3) 2 which is made up of Ba 2+ and NO 3 matches with beaker iv b) sodium chloride NaCl which is made up of Na + and Cl matches with beaker ii 1

2 c) potassium carbonate K 2CO 3 which is made up of K + and CO 3 2 matches with beaker iii d) magnesium sulfate MgSO 4 which is made up of Mg 2+ and SO 4 2 matches with beaker i 21. a) L NaOH g NaOH L NaOH mol NaOH g NaOH mol NaOH g NaOH 2.00 L( )( ) 20.0 g NaOH NaOH 1 mol NaOH 20.0 g of NaOH would be put into a volumetric flask and then water would be added to the 2.00 L mark. b) M 1 V 1 M 2 V 2 (1.00 M)(V 1 ) (0.250M)(2.00L) V L L of the 1.00 M stock solution would be put into a volumetric flask and then water would be added to the 2.00 L mark. c) L K 2CrO 4 g K 2CrO 4 L K 2CrO 4 mol K 2CrO 4 g K 2CrO L K 2 CrO 4 ( mol K 2CrO 4 K 2 CrO 4 ) ( g K 2CrO 4 1 mol K 2 CrO 4 ) 38.8 g K 2 CrO g of K 2CrO 4 would be put into a volumetric flask and then water would be added to the 2.00 L mark. d) M 1 V 1 M 2 V 2 (1.75 M)(V 1 ) (0.100M)(2.00L) V L L of the 1.75 M stock solution would be put into a volumetric flask and then water would be added to the 2.00 L mark 26. a) Ca(NO 3) 2(s) Ca 2+ (aq) + 2NO 3 (aq) V ml ( Calculate the molarity of Ca 2+ ) L 1 mol Ca2+ n Ca mol Ca(NO 3 ) 2 ( ) mol Ca 2+ 1 mol Ca(NO 3 ) 2 M n mol 1.00 M Ca2+ V L Calculate the molarity of NO 3 2 mol NO 3 n NO mol Ca(NO 3 ) 2 ( ) mol NO 1 mol Ca(NO 3 ) 3 2 M n mol V L 2.00 M NO 3 b) Na 2SO 4(s) 2Na + 2 (aq) + SO 4 (aq) V 1.25 L Calculate the molarity of Na + 2 mol Na+ n Ca mol Na 2 SO 4 ( ) 5.0 mol Na + 1 mol Na 2 SO 4 M n 5.0 mol 4.0 M Na+ V 1.25 L 2

3 Calculate the molarity of SO 4 2 n SO mol Na 2 SO 4 ( 1 mol SO mol Na 2 SO 4 ) 2.5 mol SO 4 2 M n 2.5 mol V 1.25 L 2.0 M SO 4 2 c) NH 4Cl(s) NH 4+ (aq) + Cl (aq) V ml ( ) L Calculate the molarity of NH 4 + g NH 4Cl mol NH 4Cl mol NH g NH 4 Cl ( 1 mol NH 4Cl ) ( 1 mol NH + 4 ) mol NH g NH 4 Cl 1 mol NH 4 Cl 4 + M n mol V L M NH 4 + Calculate the molarity of Cl g NH 4Cl mol NH 4Cl mol Cl 5.00 g NH 4 Cl ( 1 mol NH 4Cl 1 mol Cl ) ( ) mol Cl g NH 4 Cl 1 mol NH 4 Cl M n mol M Cl V L d) K 3PO 4(s) 3K + 3 (aq) + PO 4 (aq) V ml ( ) L Calculate the molarity of K + g K 3PO 4 mol K 3PO 4 mol K + 3 mol K g K 3 PO 4 ( 1 mol K 3PO 4 ) ( ) mol K g K 3 PO 4 1 mol K 3 PO 4 M n mol M K+ V L 3 Calcualte the molarity of PO 4 g K 3PO 4 mol K 3PO 4 mol PO g K 3 PO 4 ( 1 mol K 3PO 4 ) ( 1 mol PO ) mol PO g K 3 PO 4 1 mol K 3 PO 4 4 M n V mol L M PO Calculate the number of moles of Na + in 70.0 ml of 3.0 M Na 2CO 3 M n V V 70.0 ml ( ) L n Na2 CO 3 MV (3.0 M)( L) 0.21 mol Na 2 CO 3 2 mol Na+ n Na mol Na 2 CO 3 ( ) 0.42 mol Na + 1 mol Na 2 CO 3 Calculate the number of moles of Na + in 30.0 ml of 1.0 M NaHCO 3 M n V V 30.0 ml ( ) L n NaHCO3 MV (1.0 M)( L) mol NaHCO 3 1 mol Na+ n Na mol NaHCO 3 ( ) mol Na + 1 mol NaHCO 3 3

4 Calculate total moles of Na + n total moles Na mol mol 0.45 mol Na + Calculate the total volume V total L L L Calculate the molarity of Na + ions M n 0.45 mol 4.5 M Na+ V L 28. Calculate molarity of stock solution 25.0 g (NH 4 ) 2 SO 4 ( 1 mol (NH 4 ) 2SO g (NH 4 ) 2 SO 4 ) mol (NH 4) 2 SO 4 M n V mol (NH 4) 2 SO M (NH L 4 ) 2 SO 4 Calculate molarity of the diluted solution M 1 V 1 M 2 V 2 (1.89 M)( L) M 2 ( L) M M (NH 4 ) 2 SO 4 + Calculate molarity of NH 4 ions 2 mol NH M (NH 4 ) + 2 SO 4 ( ) M NH 1 mol (NH 4 ) 2 SO Calculate the molarity of SO 4 ions M (NH 4 ) 2 SO 4 ( 1 mol SO ) M SO 1 mol (NH 4 ) 2 SO Stock Solution n Mn g Mn ( 1 mol Mn g Mn ) mol Mn All of the Mn 2+ came from the Mn(s) therefore n Mn n Mn 2+ n Mn mol Mn ( M n mol V L Solution A M 1 V 1 M 2 V 2 V ml ( V ml ( 1 mol Mn2+ 1 mol Mn M Mn 2+ ) L ) L ( M)( L) M 2 ( L) M M Mn 2+ Solution B M 1 V 1 M 2 V 2 V ml ( V ml ( ) L ) L ( M)( L) M 2 ( L) M M Mn 2+ Solution C M 1 V 1 M 2 V 2 V ml ( V ml ( ) L ) L ) mol Mn2+ 4

5 ( M)( L) M 2 ( L) M M Mn Reaction that occurs: Pb(NO 3) 2(s) + 2KI(aq) 2KNO 3(aq) + PbI 2(s) Complete ionic equation: Pb 2+ (aq)+2no 3 (aq)+2k + (aq)+2i (aq) 2K + (aq)+2no 3 (aq)+pbi 2(s) Yes the solution will still conduct electricity because there will be K + and NO 3 ions in solutions. Note: all of the Pb 2+ moles (1.0 mol) and the I moles (2.0 mol) will go into forming the solid therefore, there will be none of these ions in solution. 39. a) (NH 4) 2SO 4(aq) + Ba(NO 3) 2(aq) 2NH 4NO 3(aq) + BaSO 4(s) 2 2NH 4+ (aq) + SO 4 (aq) + Ba 2+ (aq) + 2NO 3 (aq) 2NH 4+ (aq) + 2NO 3 (aq) + BaSO 4(s) 2 SO 4 (aq) + Ba 2+ (aq) BaSO 4(s) b) Pb(NO 3) 2(aq) + 2NaCl(aq) 2NaNO 3(aq) + PbCl 2(s) Pb 2+ (aq) + 2NO 3 (aq) + 2Na + (aq) + 2Cl (aq) 2Na + (aq) + 2NO 3 (aq) + PbCl 2(s) Pb 2+ (aq) + 2Cl (aq) PbCl 2(s) c) Na 3PO 4(aq) + 3KNO 3(aq) 3NaNO 3(aq) + K 3PO 4(aq) 3Na + 3 (aq) + PO 4 (aq) + 3K + (aq) + 3NO 3 (aq) 3Na + (aq) + 3NO 3 (aq) + 3K + 3 (aq) + PO 4 (aq) No reaction d) NaBr(aq) + RbCl(aq) NaCl(aq) + RbBr(aq) Na + (aq) + Br (aq) + Rb + (aq) + Cl (aq) Na + (aq) + Cl (aq) + Rb + (aq) + Br (aq) No reaction e) CuCl 2(aq) + 2NaOH(aq) Cu(OH) 2(s) + 2NaCl(aq) Cu 2+ (aq) + 2Cl (aq) + 2Na + (aq) + 2OH (aq) Cu(OH) 2(s) + 2Na + (aq) + 2Cl (aq) Cu 2+ (aq) + 2OH (aq) Cu(OH) 2(s) 40. There are multiple ways to do these problems; this is one way to do them a) 1. Add NaCl to the solution this will cause AgCl to precipitate 2. Add Na 2SO 4 to the solution this will cause BaSO 4 to precipitate (Note: steps one and two could have been switched.) 3. The Cr 3+ ions will be left in solution b) 1. Add Li 2SO 4 to the solution this will cause PbSO 4 to precipitate 2. Add LiCl to the solution this will cause AgCl to precipitate (Note: steps one and two cannot be switch because if the Cl was added first both PbCl 2 and AgCl would have precipitated out.) 3. The Cu 2+ ions will be left in solution c) 1. Add CaCl 2 to the solution this will cause Hg 2Cl 2 to precipitate 2. The Ni 2+ ions will be left in solution 42. There are multiple ways to do these problems; this is one way to do them. a) 3NaOH(aq) + FeCl 3(aq) Fe(OH) 3(s) + 3NaCl(aq) b) Hg 2(NO 3) 2(aq) + BaCl 2(aq) Hg 2Cl 2(s) + Ba(NO 3) 2(aq) c) K 2SO 4(aq) + Pb(NO 3) 2(aq) PbSO 4(s) + 2KNO 3(aq) d) (NH 4) 2CrO 4(aq) + BaCl 2(aq) BaCrO 4(s) + 2NH 4Cl(aq) 5

6 44. 2Na 3PO 4(aq) + 3Pb(NO 3) 2(aq) 6NaNO 3(aq) + Pb 3(PO 4) 2(s) ml Pb(NO 3) 2 mol Pb(NO 3) 2 mol Na 3PO 4 L Na 3PO ml Pb(NO 3 ) 2 ( ) (0.250 mol Pb(NO 3 ) 2 ) ( 2 mol Na 3PO 4 Na ) ( 3 PO 4 ) L Pb(NO 3 ) 2 3 mol Pb(NO 3 ) mol Na 3 PO AgNO3(aq) + CaCl2(aq) 2AgCl(s) + Ca(NO3)2(aq) This is a limiting reagent problem Calculate the moles of AgNO ml AgNO 3 ( ) (0.20 mol AgNO 3 ) mol AgNO AgNO 3 3 Calculate the moles of CaCl ml CaCl 2 ( ) (0.15 mol CaCl 3) mol CaCl CaCl 2 2 Calculate the number of moles of CaCl2 needed to fully react AgNO mol AgNO 3 ( 1 mol CaCl 2 ) mol CaCl 2 mol AgNO 2 3 Since we have mol of CaCl2 the AgNO3 is the limiting reagent. AgNO 3(aq) (L.R) CaCl 2(aq) AgCl(s) Ca(NO 3) 2 I (mol) C (mol) 2x0.020 x x x0.010 F (mol) x 0 x Calculate the grams of AgCl produced mol AgCl ( g AgCl 1 mol AgCl ) 2.9 g AgCl Calculate the concentration of the all the ions. Final Volume of Solutions ml ml ml ( ) L Calculate the concentration of Ag + ion 0 M Ag + all went into forming AgCl Calculate the molarity of Cl ions M n 0.05 M Cl from the CaCl2 V Calculate the molarity of Ca + ions 2(0.005 mol) L M n M Ca + from the Ca(NO3)2 and CaCl2 V Calculate the concentration of NO3 ions M n V mol mol L 2(0.010 mol) L 0.10M NO 3 from the Ca(NO3)2 49. Na 2CrO 4(aq) + 2AgNO 3(aq) 2NaNO 3(aq) + Ag 2CrO 4(s) ml AgNO 3 L AgNO 3 mol AgNO 3 mol Na 2CrO 4 g Na 2CrO ml AgNO 3 ( ) (0.1 mol AgNO 3 ) ( 1 mol Na 2CrO 4 ) ( g Na 2CrO 4 AgNO 3 2 mol AgNO g Na 2 CrO 4 1 mol Na 2 CrO 4 ) 6

7 53. g BaSO 4 mol BaSO 4 mol C 7H 5NO 3S g C 7H 5NO 3S g BaSO 4 ( 1 mol BaSO 4 ) g BaSO (1 mol C 7H 5 NO 3 S ) ( 1 mol C 7H 5 NO 3 S ) 4 1 mol BaSO 4 1 mol S in C 7 H 5 NO 3 S ( g C 7H 5 NO 3 S ) 1 mol C 7 H 5 NO 3 S g C 7 H 5 NO 3 S This is the amount of saccharin in 10 tablets therefore there is g of saccharin in one tablet. The mass of 10 tablets is g and the mass of the saccharin in 10 tablets is g g saccharin per tablet 10 The average mass % saccharin g ( ) 100% 67.02% g 55. M 2SO 4(aq) + CaCl 2(aq) 2MCl(aq) + CaSO 4(s) g CaSO 4 mol CaSO 4 mol M 2SO g CaSO 4 ( 1 mol CaSO 4 ) ( 1 mol M 2SO 4 ) mol M g CaSO 4 1 mol CaSO 2 SO 4 4 M M2 SO 4 m n 1.42 g mol 142 g mol M M2 SO 4 2M M + M S + 4M O g 142 2M g mol M (16.00 g ) mol mol g M M 23 mol Since the molar mass is 23 the metal is sodium (Na) 61. V NaOH mol NaOH mol acid V acid 50.0 ml NaOH ( ) L NaOH L NaOH ( mol NaOH NaOH ) mol NaOH a) NaOH(aq) + HCl(aq) NaCl(aq) + H 2O(l) 1 mol HCl mol NaOH ( ) ( HCl ) L HCl 1 mol NaOH mol HCl b) 2NaOH(aq) + H 2SO 4(aq) Na 2SO 4(aq) + 2H 2O(l) mol NaOH ( 1 mol H 2SO 4 2 mol NaOH ) ( H 2 SO mol H 2 SO 4 ) L H 2 SO 4 c) 3NaOH(aq) + H 3PO 4(aq) Na 3PO 4(aq) + 3H 2O(l) mol NaOH ( 1 mol H 3PO 4 3 mol NaOH ) ( H 3 PO mol H 3 PO 4 ) L H 3 PO 4 d) NaOH(aq) + HNO 3(aq) NaNO 3(aq) + H 2O(l) mol NaOH ( 1 mol HNO 3 1 mol NaOH ) ( HNO mol HNO 3 ) L HNO 3 e) NaOH(aq) + HC 2H 3O 2(aq) NaC 2H 3O 2(aq) + H 2O(l) mol NaOH ( 1 mol HC 2H 3 O 2 1 mol NaOH ) ( HC 2 H 3 O mol HC 2 H 3 O 2 ) L HC 2 H 3 O 2 f) 2NaOH(aq) + H 2SO 4(aq) Na 2SO 4(aq) + 2H 2O(l) mol NaOH ( 1 mol H 2SO 4 2 mol NaOH ) ( H 2 SO mol H 2 SO 4 ) L H 2 SO NaOH(aq) + KHC 8H 4O 4(aq) NaKC 8H 4O 4(aq) + H 2O(l) g KHP mol KHP mol NaOH g KHP ( 1 mol KHP mol NaOH ) ( g 1 mol KHP ) mol NaOH 7

8 Calculate the molarity of the NaOH solution V ml ( M n V mol L ) L M NaOH 66. 3Ba(OH) 2(aq) + 2H 3PO 4(aq) Ba 3(PO 4) 2(aq) + 6H 2O(l) ml H 3PO 4 L H 3PO 4 mol H 3PO 4 mol Ba(OH) 2 V Ba(OH) ml H 3 PO 4 ( ) (0.141 mol H 3PO 4 ) ( 3 mol Ba(OH) 2 ) ( H 3 PO 4 2 mol H 3 PO L Ba(OH) 2 Ba(OH) 2 ) mol Ba(OH) a) HC 2H 3O 2(aq) + NaOH(aq) NaC 2H 3O 2(aq) + H 2O(l) ml NaOH L NaOH mol NaOH mol HC 2H 3O ml NaOH ( mol NaOH ) ( ) mol HC NaOH 2 H 3 O 2 Calculate the molarity of the acetic acid V 10.0 ml ( ) L M n mol M HC V L 2 H 3 O 2 b) Calculate the mass of the acetic acid mol HC 2 H 3 O 2 ( g HC 2H 3 O 2 1 mol HC 2 H 3 O 2 ) g Calculate the mass of the vinegar in 10.0 ml ml ( 1 cm3 1 ml Calculate the mass % g ) ( cm ( m HC 2 H 3 O 2 ) 100% ( m total 3 ) g g ) 100% 5.011% g 71. This is a limiting reagent problem. Find out if OH or H + is present in excess. 2HCl(aq) + Ba(OH) 2(aq) BaCl 2(aq) + 2H 2O(l) Net Ionic Equations: H + (aq) + OH (aq) H 2O(l) Determine the initial moles of H ml HCl ( Determine the initial moles of OH mol HCl ) (0.250 HCl ) ( 1 mol H+ 1 mol HCl ) mol H ml Ba(OH) 2 ( ) (0.250 mol Ba(OH) 2 2 mol OH ) ( ) mol OH Ba(OH) 2 1 mol Ba(OH) 2 Calculate the number of moles of OH needed to fully react with mol H + 1 mol HCl ) 1 mol H + (1 mol Ba(OH) 2 2 mol HCl 2 mol OH mol H + ( ) ( ) mol OH 1 mol Ba(OH) 2 Since we have moles of OH, H + is the limiting reagent and will be completely consumed. H + (aq) (L.R) OH (aq) H 2O(l) I (mol) C (mol) x x x F (mol) x 0 x

9 Calculate the molarity of OH left in solution. V 75.0 ml ml ml ( M n mol M OH V L ) L 75. a) K +1, Mn +7, and O 2 b) Ni +4, and O 2 c) Fe +2 d) NH 4 +1 (N 3 and H +1), and HPO 4 2 (H +1, P +5, and O 2) e) P +3, and O 2 f) Fe +8/3, and O 2 g) Xe +6, O 2, and F 1 h) S +4, and F 1 i) C +2, and O 2 j) C 0, H +1, and O a) Sr 2+, Cr +6, and O 2 b) Cu +2, and Cl 1 c) O 0 d) H +1 and O 1 (peroxide) e) Mg +2, C +4, and O 2 f) Ag 0 g) Pb 2+, and SO 3 2 (S +4 and O 2) h) Pb 4+, and O 2 i) Na +1, C +3, and O 2 j) C +4, and O 2 k) NH 4 +1 (N 3 and H +1), Ce 4+, and SO 4 2 (S +6 and O 2) l) Cr +3, and O Since they ask for substance oxidized they want entire compound not just element oxidized a) Redox reaction Element Beginning Oxidation # Ending Oxidation # O 0 2 C 4 +4 O is reduced, O 2 is species reduced C is oxidized, CH 4 is species oxidized O 2 is the oxidizing agent CH 4 is the reducing agent b) Redox reaction Element Beginning Oxidation # Ending Oxidation # Zn 0 +2 H +1 0 Zn is oxidized H is reduced, HCl is species reduced Zn is the reducing agent HCl is the oxidizing agent c) Not a redox reaction d) Redox Reaction Element Beginning Oxidation # Ending Oxidation # O 0 2 N O is reduced, O 3 is species reduced N is oxidized, NO is species oxidized O 3 is the oxidizing agent NO is the reducing agent 9

10 e) Redox Reaction Element Beginning Oxidation # Ending Oxidation # O 1 0 O 1 2 O is reduced, H 2O 2 is species reduced O is oxidized, H 2O 2 is species oxidized H 2O 2 is the oxidizing agent H 2O 2 is the reducing agent f) Redox Reaction Element Beginning Oxidation # Ending Oxidation # Cu +1 0 Cu Cu is reduced, CuCl is species reduced Cu is oxidized, CuCl is species oxidized CuCl is the oxidizing agent CuCl is the reducing agent g) Not a Redox Reaction h) Not a Redox Reaction i) Redox Reaction Element Beginning Oxidation # Ending Oxidation # Si +4 0 Mg 0 +2 Si is reduced, SiCl 4 is species reduced Mg is oxidized SiCl 4 is the oxidizing agent Mg is the reducing agent 71. a) Cu Cu 2+ Cu Cu e Balance Reduction ½ Reaction NO 3 NO NO 3 NO + 2H 2O NO 3 + 4H + NO + 2H 2O NO 3 + 4H + + 3e NO + 2H 2O 3(Cu Cu e ) 2(NO 3 + 4H + +3e NO + 2H 2O) 3Cu(s) + 2NO 3 (aq) + 8H + (aq) 3Cu 2+ (aq) + 2NO(g) + 4H 2O(l) b) Balance Recution ½ Reaction 2 7 Cr Cr Cr H 2O H + 2Cr H 2O H + + 6e 2Cr H 2O 10

11 Cl Cl 2 2Cl Cl 2 2Cl Cl 2 + 2e H + + 6e 2Cr H 2O 3(2Cl Cl 2 + 2e ) 7 2 (aq) + 14H + (aq) + 6Cl (aq) 2Cr 3+ (aq) + 7H 2O(l) + 3Cl 2(g) c) Balance Reduction ½ Reaction PbO 2 + H 2SO 4 PbSO 4 PbO 2 + H 2SO 4 PbSO 4 + 2H 2O PbO 2 + H 2SO 4 + 2H + PbSO 4 + 2H 2O PbO 2 + H 2SO 4 + 2H + + 2e PbSO 4 + 2H 2O Pb + H 2SO 4 PbSO 4 Pb + H 2SO 4 PbSO 4 + 2H + Pb + H 2SO 4 PbSO 4 + 2H + + 2e PbO 2 + H 2SO 4 + 2H + + 2e PbSO 4 + 2H 2O Pb + H 2SO 4 PbSO 4 + 2H + + 2e PbO 2(s) + 2H 2SO 4(aq) + Pb(s) 2PbSO 4(s)+ 2H 2O(l) d) Skip this equation. You will not be able to balence this because there is no sodium on the products side of the equation. e) Balance Reducation ½ Reaction H 3AsO 4 AsH 3 H 3AsO 4 AsH 3 + 4H 2O H 3AsO 4 + 8H + AsH 3 + 4H 2O H 3AsO 4 + 8H + + 8e AsH 3 + 4H 2O Zn Zn 2+ Zn Zn e H 3AsO 4 + 8H + + 8e AsH 3 + 4H 2O 4(Zn Zn e ) H 3AsO 4(aq) + 8H + (aq) + 4Zn(s) AsH 3(g)+ 4H 2O(l) + 4Zn 2+ (aq) f) As 2O 3 H 3AsO 4 As 2O 3 2H 3AsO 4 As 2O 3 + 5H 2O 2H 3AsO 4 As 2O 3 + 5H 2O 2H 3AsO 4 + 4H + As 2O 3 + 5H 2O 2H 3AsO 4 + 4H + + 4e Balance Reducation ½ Reaction NO 3 NO NO 3 NO + 2H 2O NO 3 + 4H + NO + 2H 2O NO 3 + 4H + +3e NO + 2H 2O 11

12 3(As 2O 3 + 5H 2O 2H 3AsO 4 + 4H + + 4e ) 4(NO 3 + 4H + +3e NO + 2H 2O) 3As 2O 3(s) + 7H 2O(l) + 4NO 3 (aq) + 4H + (aq) 6H 3AsO 4(aq) + 4NO(g) g) Br Br 2 2Br Br 2 2Br Br 2 + 2e Balance Reducation ½ Reaction Mn 2+ Mn H 2O + 8H + Mn H 2O + 8H + + 5e Mn H 2O 5(2Br Br 2 + 2e ) 2( + 8H + + 5e Mn H 2O) 10Br (aq) + 2 (aq) + 16H + (aq) 5Br 2(l) + 2Mn 2+ (aq) + 8H 2O(l) h) CH 3OH CH 2O CH 3OH CH 2O + 2H + CH 3OH CH 2O + 2H + + 2e Balance Reducation ½ Reaction 7 2 Cr Cr Cr H 2O H + 2Cr H 2O H + + 6e 2Cr H 2O Total Balance Equation 3(CH 3OH CH 2O + 2H + + 2e ) H + + 6e 2Cr H 2O 3CH 3OH(aq) (aq) + 8H + (aq) 3CH 2O(aq) + 2Cr 3+ (aq) + 7H 2O(l) 82. a) Al Al(OH) 4 Al + 4H 2O Al(OH) 4 Al + 4H 2O Al(OH) 4 + 4H + Al + 4H 2O Al(OH) 4 + 4H + + 3e Balance Reducation ½ Reaction MnO 2 MnO 2 + 2H 2O + 4H + MnO 2 + 2H 2O + 4H + + 3e MnO 2 + 2H 2O Al + 4H 2O Al(OH) 4 + 4H + + 3e + 4H + + 3e MnO 2 + 2H 2O Al(s) + 2H 2O(l) + (aq) Al(OH) 4 (aq) + MnO 2(s) Since there are no H + in the equation the equation is the same for acid or basic conditions. 12

13 b) Balance Reducation ½ Reaction Cl 2 2Cl Cl 2 + 2e 2Cl Cl 2 2ClO Cl 2 + 2H 2O 2ClO Cl 2 + 2H 2O 2ClO + 4H + Cl 2 + 2H 2O 2ClO + 4H + +2 e Cl 2 + 2e 2Cl Cl 2 + 2H 2O 2ClO + 4H + + 2e 2Cl 2(g) + 2H 2O(l) 2Cl (aq) + 2ClO (aq) + 4H + (aq) Reduce to smallest numbers Cl 2(g) + H 2O(l) Cl (aq) + ClO (aq) + 2H + (aq) Switch to basic Cl 2(g) + H 2O(l) + 2OH (aq) Cl (aq) + ClO (aq) + 2H + (aq) + 2OH (aq) Cl 2(g) + 2OH (aq) Cl (aq) + ClO (aq) + H 2O(l) c) Balance Reducation ½ Reaction NO 2 NH 3 NO 2 NH 3 + 2H 2O NO 2 + 7H + NH 3 + 2H 2O NO 2 + 7H + + 6e NH 3 + 2H 2O Al AlO 2 Al + 2H 2O AlO 2 Al + 2H 2O AlO 2 + 4H + Al + 2H 2O AlO 2 + 4H + + 3e NO 2 + 7H + + 6e NH 3 + 2H 2O 2(Al + 2H 2O AlO 2 + 4H + + 3e ) NO 2 (aq) + 2Al(s) + 2H 2O(l) NH 3(g) + 2AlO 2 (aq) + H + (aq) Switch to basic NO 2 (aq) + 2Al(s) + 2H 2O(l) + OH (aq) NH 3(g) + 2AlO 2 (aq) + H + (aq) + OH (aq) NO 2 (aq) + 2Al(s) + H 2O(l) + OH (aq) NH 3(g) + 2AlO 2 (aq) d) Balance Reduction ½ Reaction + S 2 MnS + S 2 MnS + 4H 2O + S 2 + 8H + MnS + 4H 2O + S 2 + 8H + + 5e MnS + 4H 2O S 2 S S 2 S + 2e 2( + S 2 + 8H + + 5e MnS + 4H 2O) 5(S 2 S + 2e ) 2 (aq) + 7S 2 (aq) + 16H + (aq) 2MnS(s) + 8H 2O(l) + 5S(s) 13

14 Switch to Basic 2 (aq)+7s 2 (aq)+16h + (aq)+16oh (aq) 2MnS(s)+8H 2O(l)+5S(s)+16OH (aq) 2 (aq) + 7S 2 (aq) + 8H 2O(l) 2MnS(s) + 5S(s) + 16OH (aq) e) Balance Reducation ½ Reaction CN CNO CN + H 2O CNO CN + H 2O CNO + 2H + CN + H 2O CNO + 2H + + e MnO 2 MnO 2 + 2H 2O + 4H + MnO 2 + 2H 2O + 4H + + 3e MnO 2 + 2H 2O Total Balanced Equatioin 3(CN + H 2O CNO + 2H + + e ) 2( + 4H + + 3e MnO 2 + 2H 2O) 3CN (aq) + 2 (aq) + 2H + (aq) 3CNO (aq) + 2MnO 2(s) + H 2O(l) Switch to basic conditions 3CN (aq) + 2 (aq) + 2H + (aq) + 2OH (aq) 3CNO (aq) + 2MnO 2(s) + H 2O(l) + 2OH (aq) 3CN (aq) + 2 (aq) + H 2O(l) 3CNO (aq) + 2MnO 2(s) + 2OH (aq) st balance the equation Balance Reduction ½ Reaction Mn 2+ Mn H 2O + 8H + Mn H 2O + 8H + + 5e Mn H 2O H 2C 2O 4 CO 2 H 2C 2O 4 2CO 2 H 2C 2O 4 2CO 2 + 2H + H 2C 2O 4 2CO 2 + 2H + + 2e 2( + 8H + + 5e Mn H 2O) 5(H 2C 2O 4 2CO 2 + 2H + + 2e ) 2 (aq) + 6H + (aq) + 5H 2C 2O 4(aq) 2Mn 2+ (aq) + 8H 2O(l) + 10CO 2(g) Calculate the moles of g H 2 C 2 O 4 ( 1 mol H 2C2O g H2C2O4 ) ( 2 mol 5 mol H2C2O4 ) mol Calculate the molarity of the solution M n V V ml ( M n V mol L ) L M 14

15 86. a) Balance the equation Balance Reduction ½ Reaction Mn H 2O + 8H + Mn H 2O + 8H + + 5e Mn H 2O Fe 2+ Fe 3+ Fe 2+ Fe 3+ + e + 8H + + 5e Mn H 2O 5(Fe 2+ Fe 3+ + e ) (aq) + 8H + (aq) + 5Fe 2+ (aq) Mn 2+ (aq) + 4H 2O(l) + 5Fe 3+ (aq) Calculate the moles of Fe 2+ ml K L K mol K mol mol Fe ml K ( ) ( mol K mol Fe 2+ Calculate the molarity of the Fe 2+ solution ) ( 1 mol MnO 4 ) ( K 1 mol K M n V V ml ( ) L M n mol M Fe2+ V L b) Balance the equation Balance Reduction ½ Reaction 2 7 Cr Cr Cr H 2O H + 2Cr H 2O H + + 6e 2Cr H 2O Fe 2+ Fe 3+ Fe 2+ Fe 3+ + e H + + 6e 2Cr H 2O 6(Fe 2+ Fe 3+ + e ) 2 7 (aq) + 14H + (aq) + 6Fe 2+ (aq) 2Cr 3+ (aq) + 7H 2O(l) + 6Fe 3+ (aq) Calculate the V of K 2CrO 7 mol Fe 2+ mol 2 7 mol K 2 7 V K 2CrO mol Fe 2+ ( 1 mol Cr 2 2O 7 ) 6 mol Fe 2+ (1 mol K 2Cr 2 O 7 ) ( K 2 Cr 2 O 7 1 mol Cr 2 O2 ) mol K 2 Cr 2 O L K 2 Cr 2 O 7 5 mol Fe2+ 1 mol ) 15

Chapter 4 Suggested end-of-chapter problems with solutions

Chapter 4 Suggested end-of-chapter problems with solutions a. 5.6 g NaHCO 1 mol NaHCO 84.01 g NaHCO = 6.69 10 mol NaHCO M = 6.69 10 mol 50.0 m 1000 m = 0.677 M NaHCO b. 0.1846 g K Cr O 7 1 mol K 94.0 g