Updated Feb.28/06 ----------------------------------------------------------------------------------------- NUMERICAL ANSWERS TO ASSIGNED TUTORIAL PROBLEM SETS FOR CHEM205 FROM KOTZ & TREICHEL'S CHEMISTRY & CHEMICAL REACTIVITY ----------------------------------------------------------------------------------------- NOTE: none of the answers from Ch.20 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 ----------------------------------------------------------------------------------------- 20 1a Zn = reducing agent & gets oxidized; HNO3 = oxidizing agent & gets reduced 20 1b not redox 20 1c Cu = reducing agent, is oxidized; NO3 - = oxidizing agent, is reduced 20 1d HOCl = oxidizing agent, is reduced; Cl- = reducing agent, is oxidized 20 13a ox: H2O2(aq) --> O2(g) + 2H+(aq) + 2e- 20 13b ox: H2C2O4(aq) --> 2CO2(g) + 2H+(aq) + 2e- 20 13c red: NO3 -(aq) + 4H+(aq) + 3e- --> NO(g) + 2H2O(l) 20 13d red: MnO4-(aq) + 2H2O(l) + 3e- --> MnO2(s) + 4OH-(aq) 20 15a Sn(s) --> Sn2+(aq) + 2e- 20 15a 2H+(aq) + 2e- --> H2(g) 20 15a net: Sn(s) + 2H+(aq) --> Sn2+(aq) + H2(g) 20 15b Cr2O7 2-(aq) + 14H+(aq) + 6e- --> 2Cr3+(aq) + 7H2O(l) 20 15b 6[Fe2+(aq) --> Fe3+(aq) + 1e-] 20 15b net: Cr2O7 2-(aq) + 14H+(aq) + 6Fe2+(aq) --> 2Cr3+(aq) + 7H2O(l) + 6Fe3+(aq) 20 15c MnO2(s) + 4H+(aq) + 2e- --> Mn2+(aq) + 2H2O(l) 20 15c 2Cl-(aq) --> Cl2(g) + 2e- 20 15c net: MnO2(s) + 4H+(aq) + 2Cl-(aq) --> Mn2+(aq) + 2H2O(l) + Cl2(g) 20 15d CH2O(aq) + H2O(l) --> HCO2H(aq) + 2H+(aq) + 2e- 20 15d 2[Ag+(aq) + e- --> Ag(s)] 20 15d net: CH2O(aq) + H2O(l) + 2Ag+(aq) --> HCO2H(aq) + 2H+(aq) + 2Ag(s) 20 17a net: 3Fe(OH)3(s) + Cr(s) --> 3Fe(OH)2(s) + Cr(OH)2(s) 20 17b net: NiO2(s) + 2H2O(l) + Zn(s) --> Ni(OH)2(s) + Zn(OH)2(s) 20 17c net: 3Fe(OH)3(s) + CrO4 2-(aq) + 4H2O(l) --> 3Fe(OH)3(s) + Cr(OH)4 -(aq) + OH-(aq) 20 63a Zn(s) + 2VO 2+(aq) + 4H+(aq) --> Zn2+(aq) + 2V3+(aq) + 2H2O(l) 20 63b 3Zn(s) + 2VO3 -(aq) + 12H+(aq) --> 3Zn2+(aq) + 2V3+(aq) + 6H2O(l) 20 63c Zn(s) + OCl-(aq) + H2O(l) --> Zn(OH)2(s) + Cl-(aq) 20 63d 3ClO-(aq) + 2Cr(OH)4 -(aq) + 2OH-(aq) --> 3Cl-(aq) + 2CrO4 2-(aq) + 5H2O(l)