Updated Oct.17/04 ----------------------------------------------------------------------------------------- NUMERICAL ANSWERS TO ASSIGNED TUTORIAL PROBLEM SETS FOR CHEM205 FROM KOTZ & TREICHEL'S CHEMISTRY & CHEMICAL REACTIVITY ----------------------------------------------------------------------------------------- NOTE: none of the answers from Ch.5 have been verified NOTE: "^" means "raised to the power of..." to indicate scientific notation... NOTE: I cannot represent superscripts/subscripts here -- so...for polyatomic ions, I have left a space between the ion's formula and its charge Ch. Q# Answer Units SFs Comments ----------------------------------------------------------------------------------------- 5 2a acid-base: HCl(aq) + NaOH(aq) --> H2O(l) + NaCl(aq) 5 2a acid + base yields soluble salt plus water 5 2b pptn: AgNO3(aq) + KCl(aq) --> AgCl(s) + KNO3(aq) 5 2b 2 soluble salts react to form 1 soluble salt & 1 insoluble salt 5 2c gas forming: Na2S(aq) + 2HCl(aq) --> 2NaCl(aq) + H2S(g) 5 2c a metal sulfide + acid reacts to form a soluble salt and a gas 5 2d redox: 2Na(s) + Cl2(g) --> 2NaCl(s) 5 2d an oxidizing agent, chlorine, reacts with a reducing agent, sodium, to yield sodium chloride 5 4 strong electrolytes: hydrochloric acid, nitric acid 5 4 weak electrolyte: acetic acid 5 4 strong electrolytes: sodium hydroxide, potassium hydroxide 5 4 weak electrolytes: ammonia, calcium hydroxide 5 10a oxidation = loss of electrons: e.g., Na --> Na+ + 1e- 5 10a reduction = gain of electrons: e.g., Cl2 + 2e- --> 2 Cl- 5 10b oxidizing agent is reduced during reaction: e.g., Cl2 5 10b reducing agent is oxidized during reaction: e.g., Na(s) 5 14 0.20M BaCl2 --> 0.60M ions has larger conc. of ions… 5 14 0.25M NaCl --> 0.50M ions 5 16 11 g 2 Na2CO3 5 16 how: weigh solid; add to 500.0mL flask; dissolve in small vol. H2O; then top up to mark; mix gently 5 25a soluble: Ni2+ and Cl- ions 5 25b soluble: Cr2+ and NO3 - ions 5 25c soluble: Pb2+ and NO3 - ions 5 25d insoluble 5 27 Ni(NO3)2(aq) + Na2CO3(aq) --> NiCO3(s) + 2NaNO3(aq) 5 27 Ni2+(aq) + CO3 2-(aq) --> NiCO3(s) 5 29a Pb(NO3)2(aq) + 2KBr(aq) --> PbBr2(s) + 2KNO3(aq) 5 29b Ca(NO3)2(aq) + 2KF(aq) --> CaF2(s) + 2KNO3(aq) 5 29c Ca(NO3)2(aq) + Na2C2O4(aq) --> CaC2O4(aq) + 2NaNO3(aq) 5 31a Zn(s) + 2HCl(aq) --> H2(g) + ZnCl2(aq) 5 31a Zn(s) + 2H+(aq) --> H2(g) + Zn2+(aq) 5 31b Mg(OH)2(s) + 2HCl(aq) --> MgCl2(aq) + 2H2O(l) 5 31b Mg(OH)2(s) + 2H+(aq) --> Mg2+(aq) + 2H2O(l) 5 31c 2HNO3(aq) + CaCO3(s) --> Ca(NO3)2(aq) + H2O(l) + CO2(g) 5 31c 2H+(aq) + CaCO3(s) --> Ca2+(aq) + H2O(l) + CO2(g) 5 33a 2NaOH(aq) + FeCl2(aq) --> Fe(OH)2(s) + 2NaCl(aq) 5 33a 2OH-(aq) + Fe2+(aq) --> Fe(OH)2(s) 5 33b BaCl2(aq) + Na2CO3(aq) --> BaCO3(s) + 2NaCl(aq) 5 33b Ba2+(aq) + CO3 2-(aq) --> BaCO3(s) 5 37 H3PO4(aq) --> H+(aq) + H2PO4 -(aq) 5 37 H2PO4 -(aq) --> H+(aq) + HPO4 2-(aq) 5 37 HPO4 2-(aq) --> H+(aq) + PO4 2-(aq) 5 41a H3PO4(aq) + 3KOH(aq) --> K3PO4(aq) + 3H2O(l) 5 41a phosphoric acid, potassium hydroxide, potassium phosphate, water 5 41b H2C2O4(aq) + Ca(OH)2(s) --> CaC2O4(s) + 2H2O(l) 5 41b oxalic acid, calcium hydroxide, calcium oxalate, water 5 49a Fe(OH)3(s) + 3HNO3(aq) --> Fe(NO3)3(aq) + 3H2O(l) 5 49a acid-base reaction 5 49a Fe(OH)3(s) + 3H+(aq) --> Fe3+(aq) + 3H2O(l) 5 49b FeCO3(s) + 2HNO3(aq) --> Fe(NO3)2(aq) + CO2(g) + H2O(l) 5 49b acid-base reaction, & gas-forming reaction 5 49b FeCO3(s) + 2H+(aq) --> Fe2+(aq) + CO2(g) + H2O(l) 5 53a P is +5 (V); F is -1 (-I) 5 53b H is +1 (+I); As is +5 (+V); O is -2 (-II) 5 53c U is +4 (+IV); O is -2 (-II) 5 53d N is +5 (+V); O is -2 (-II) 5 53e P is +5 (V); O is -2 (-II); Cl is -1 (-I) 5 53f Xe is +6 (+VI); O is -2 (-II) 5 55a precipitation 5 55b redox: Ca from 0 to +2; O from 0 to -2 5 55c redox: Fe from +2 to +3; O from 0 to -2 5 57a Cr2O7 2- is reduced (oxidizing agent); Sn2+ is oxidized (reducing agent) 5 57b FeS is oxidized (reducing agent); NO3 - is reduced (oxidizing agent) 5 59 0.0159 M 3 K2Cr2O7 Thus, [K+]=0.0318M; [Cr2O7 2-]=0.0159M 5 65a 0.12M Ba2+; 0.24M Cl- 5 65b 0.0125M Cu2+; 0.0125M SO4 2- 5 65c 1.000M K+; 0.500M Cr2O7 2- 5 67 3.4 g 2 H2C2O4 5 71a 0.150 M 3 K2Cr2O7 5 71b 0.500 M 3 K2Cr2O7 correct method 5 73 3x10^-11 M 1 H+ conc.; solution is acidic (pH < 7) 5 77a 9.17 2 (recall SF rule for logs...) pH > 7 therefore basic 5 77b 5.66 2 pH < 7 therefore acidic 5 77c 5.6x10^-6 M 2 pH < 7 therefore acidic 5 77d 1.60 2 pH < 7 therefore acidic 5 81 2.34 g 3 N2H4 5 83 10.2 g 3 mass KAl(OH)4 because Al is limiting reagent (thus none remains) 5 87 42.5 mL 3 volume HCl(aq) required to reach equivalence point 5 91 0.0149 mol 3 NaOH required 5 91 0.00498 mol 3 if citric acid…this #mol would lead to calculated MM = 192 g/mol (correct for citric acid) 5 91 0.00746 mol 3 if tartaric acid…this #mol leads to MM = 128 g/mol (which is NOT correct, so it can't be tartaric acid…) 5 97a (NH4)2S(aq) + Hg(NO3)2(aq) --> HgS(s) + 2NH4NO3(aq) 5 97b ammonium sulfide, mercury(II) nitrate, mercury(II) sulfide, ammonium nitrate 5 97c precipitation 5 101 0.219 g 3 mass of citric acid in soft drink 5 103 3.13 g 3 Na2S2O3; sample was 96.8% sodium thiosulfate by weight 5 105a Pb(NO3)2(aq) + 2KOH(aq) --> Pb(OH)2(s) + 2KNO3(aq) 5 105b lead(II) nitrate, potassium hydroxide, lead(II) hydroxide, potassium nitrate 5 105c Pb2+(aq) + 2OH-(aq) --> Pb(OH)2(s) 5 107a Cu(NO3)2(aq) + Na2CO3(aq) --> CuCO3(s) + 2NaNO3(aq) 5 107b copper(II) nitrate, sodium carbonate, copper(II) carbonate, sodium nitrate 5 107c Cu2+(aq) + CO3 2-(aq) --> CuCO3(s) 5 113 0.00110 M 3 Na2CO3 conc. in diluted solution 5 121 7.6x10^4 L 2 volume of water in pool…