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1 xam 4 Wrksheet Answers xam 4 Wrksheet Answers Chemistry 104 Chapter 19 lectrchemistry ( repeated frm xam 3 wrksheet) 1. What is the xidatin state f each element? 0 0 d. 0 e. f. g. 0. What is the xidatin state f each element? Li: O: H: Fe: 3 O: S: 6 Al: 3 O: N: 5 d. C: 4 O: e. C: O: f. I: 7 Cl: g. Cd: O: P: 5 h. Mn: 4 O: 3. Balance the x reactins, identifying fr each which species is gaining r lsing electrns, and which is xidatin and which is uctin. Fe ( aq) e Fe( s) gaining electrns / uctin Ag ( s) Ag ( aq) e lsing electrns / xidatin Net inic: Fe ( aq) Ag ( s) Fe( s) Ag ( aq) Overall: Fe NO aq Ag s Fe s AgNO aq 3 3 Cl aq Cl g e lsing electrns / xidatin Zn aq e Zn s gaining electrns / uctin Net inic: Cl aq Zn aq Zn s Cl g Overall: NaCl aq Zn NO aq Zn s Cl g NaCl aq Au aq 3e Au s gaining electrns / uctins Cu s Cu aq e lsing electrns / xidatin Net inic: Au aq 3Cu s 3Cu aq Au s Overall: Au NO aq 3Cu s 3Cu NO aq Au s

2 xam 4 Wrksheet Answers d. F g e F aq gaining electrns / uctin H O aq O g 4e 4H aq lsing electrns / xidatin Net inic: F g H O aq 4HF aq O g Overall: F g H O aq 4HF aq O g 4. Balance the x reactins in acidic slutin, identifying each half reactin as xidatin r uctin. SO aq 4H aq e SO g H O l uctin 4 Fe s Fe aq e xidatin H SO aq Fe s SO g H O l FeSO aq 4 4 d. e. f. () 3 7 H O l O g 4H aq 4e uctin Cr O aq 14H aq 6e Cr aq 7H O l xidatin 3 7 Net inic: Cr O aq 16H aq 3O g 4Cr aq 8H O l Overall: H Cr O aq 1HNO aq 3O g 4Cr NO aq 8H O l PbO s SO aq 4H aq e PbSO s H O l uctin Pb s SO aq e PbSO s xidatin PbO s Pb s SO aq 4H aq PbSO s H O l SO g H O l SO aq 4H aq e xidatin I s e I aq uctin Net inic: SO g H O l I s I aq SO aq 4H aq Overall: SO g H O l I s HI aq H SO aq 4 3 Br aq Br l e xidatin NO aq 4H aq 3e NO g H O l uctin 3 Net inic: 6Br aq NO aq 8H aq 3Br l NO g 4H O l Overall: 6HBr aq HNO aq 3Br l NO g 4H O l 3 MnO s 4H aq e Mn aq H O l uctin Cl aq Cl g e xidatin MnO s 4H aq Cl aq Mn aq Cl g H O l Overall : MnO s 4HCl aq MnCl aq Cl g H O l

3 xam 4 Wrksheet Answers g. h. MnO s 4H aq e Mn aq H O l uctin Br aq Br l e xidatin MnO s 4H aq Br aq Mn aq Br l H O l Overall : MnO s 4HBr aq MnBr aq Br l H O l 3 3 Cu s Cu aq e xidatin NO aq 4H aq 3e NO g H O l uctin NO g 4H O l 3Cu aq 3Cu s NO aq 8H aq Overall: NO g 4H O l 3Cu NO aq 3Cu s 8HNO aq Balance the x reactins in basic slutin, identifying each half reactin as xidatin r uctin. H g OH aq H O l e xidatin e Cu aq Cu s uctin H g Cu aq OH aq H O l Cu s Ni s Ni aq e xidatin O g H O l 4e 4OH aq uctin O g H O l Ni s Ni OH s 4 () () MnO s 4OH aq MnO aq H O l 3e xidatin Br l e Br l uctin MnO s 8OH aq 6Br l MnO aq 4H O l 3Br l 4 6. Fr the reactins yu balanced in number three answer: Fe aq e Fe s = 0.44 V cathde reactin; cathde = Fe s Ag ( s) Ag ( aq) e x = 0.80 V ande reactin; ande = Ag ( s) cell = 1.4 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm irn t silver) Ag(s) Ag (aq) (1 M) ǁ Fe (aq) (1 M) Fe(s) x = = = = Cl aq Cl g e 1.36 V ande reactin; ande Pt s Zn aq e Zn s 0.76 V cathde reactin; cathde Zn s cell =.1 V 3

4 xam 4 Wrksheet Answers Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm zinc t platinum) Zn (aq) (1 M) Zn(s) ǁ Cl (aq) (1 M) Cl (g) Pt(s) d. 3 = = = = Au aq 3e Au s 1.50 V cathde reactin; cathde Au s Cu s Cu aq e 0.34 V ande reactin; ande Cu s x cell = 1.16 V electrns flw frm cpper t gld (ande t cathde) Spntaneus Au 3 (aq) (1 M) Au(s) ǁ Cu(s) Cu (aq) (1 M) = = = = F g e F aq.87 V cathde reactin; cathde Pt s H O aq O g 4e 4H aq 1.3 V ande reactin; ande Pt s x cell = 1.64 V electrns flw frm ande t cathde Spntaneus Pt(s) F (g) F (aq) (1 M) ǁ H O(l) O (g) Pt(s) 7. Fr the reactins yu balanced in number fur answer: SO4 ( aq) 4H ( aq) e SO( g) HO( l ) = 0.0 V cathde reactin; cathde = Pt s Fe s Fe aq e x = 0.44 V ande reactin; ande = Fe s cell = 0.4 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm platinum t irn) () H O l O g 4H aq 4e x 3 7 = 1.3 V ande reactin; ande = Pt s Cr O aq 14H aq 6e Cr aq 7H O l = 1.33 V cathde reactin; cathde = Pt s cell = 0.10 V electrns flw frm ande t cathde Spntaneus PbO s SO aq 4H aq e PbSO s H O l 4 4 Pb s SO aq e PbSO s 4 4 x = 1.70 V cathde reactin; cathde = PbO s = 0.31 V ande reactin; ande = Pb s cell =.01 V electrns flw frm lead t lead(iv) xide (ande t cathde) Spntaneus 4

5 xam 4 Wrksheet Answers d. e. f. g. h. SO g H O l SO aq 4H aq e 4 x I s e I aq cell = 0.33 V Spntaneus Br aq Br l e = 0.0 V ande reactin; ande = Pt s = 0.53 V cathde reactin; cathde = Pt s electrns flw frm ande t cathde x 3 = 1.07 V ande reactin; ande = Pt s NO aq 4H aq 3e NO g H O l = 0.96 V cathde reactin; cathde = Pt s cell = 0.11 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm platinum (Br uctin) t platinum (NO xidatin)) MnO s 4H aq e Mn aq H O l 1.3 V cathde reactin; cathde MnO s = = Cl aq Cl g e x = 1.36 V ande reactin; ande = Pt s cell = 0.13 V Nt spntaneus (reverse reactin is spntaneus, s electrns wuld spntaneusly flw frm MnO t platinum) MnO s 4H aq e Mn aq H O l 1.3 V cathde reactin; cathde MnO s = = Br aq Br l e cell = 0.16 V Spntaneus Cu s Cu aq e x = 1.07 V ande reactin; ande = Pt s electrns flw frm platinum t MnO (ande t cathde) x 3 NO aq 4H aq 3e NO g H O l cell = 0.6 V cathde) = 0.34 V ande reactin; ande = Cu s = 0.96 V cathde reactin; cathde = Pt s electrns flw frm cpper t platinum (ande t Spntaneus 5

6 xam 4 Wrksheet Answers 8. Fr the reactins yu balanced in number five answer: H g OH aq H O l e x e Cu aq Cu s = 0.83 V ande reactin; ande = Pt s = 0.34 V cathde reactin; cathde = Cu s cell = 1.17 V electrns flw frm platinum t cpper (ande t cathde) Spntaneus Ni s Ni aq e x O g H O l 4e 4OH aq = 0.5 V ande reactin; ande = Ni s = 0.40 V cathde reactin; cathde = Pt s cell = 0.65 V electrns flw frm nickel t platinum (ande t cathde) Spntaneus MnO s 4OH aq MnO aq H O l 3e 4 () () Br l e Br l x = 0.59 V ande reactin; ande = MnO s = 1.07 V cathde reactin; cathde = Pt s cell = 0.48 V electrns flw frm MnO t platinum (ande t cathde) Spntaneus 9. What is the standard change in free energy and the equilibrium cnstant at 5 C fr the reactins yu balanced in number 3? ΔG (kj) K A B C 67 D What is the standard change in free energy and the equilibrium cnstant at 5 C fr the reactins yu balanced in number 4? ΔG (kj) K A B

7 xam 4 Wrksheet Answers ΔG (kj) K C D F G H What is the standard change in free energy and the equilibrium cnstant at 5 C fr the reactins yu balanced in number 5? ΔG (kj) K A B C What is the cell ptential at 5 C f the cells described belw? Are these spntaneus? Reactin (V) Spntaneus A Pb(s) Pb ( M) ǁ Ni (0.875 M) Ni(s) 0.04 N B Pb(s) Pb (0.875 M) ǁ Ni ( M) Ni(s) 0.0 N C Ni(s) Ni (0.875 M) ǁ Pb ( M) Pb(s) 0.04 Yes D Ni(s) Ni ( M) ǁ Pb (0.875 M) Pb(s) 0.0 Yes Pb(s) Pb ( M) ǁ Cr 3 (0.875 M) Cr(s) 0.53 N F Cr(s) Cr 3 (0.750 M) ǁ Ag (0.005 M) Ag(s) 1.39 Yes G Ag(s) Ag (0.750 M) ǁ Au 3 (0.005 M) Au(s) 0.63 Yes H Pt(s) I (0.05 M) I (s) ǁ Ag (0.750 M) Ag(s) 0.36 Yes I Pt(s) I (0.005 M) I (s) ǁ Ag (0.750 M) Ag(s) 0.30 Yes J Pt(s) Br (0.005 M) Br (l) ǁ Ag (0.750 M) Ag(s) 0.43 N 13. What is the cell ptential at 5 C f the cells described belw? Are these spntaneus? Reactin (V) Spntaneus A Zn(s) Zn ( M) ǁ Zn (0.75 M) Zn(s) 0.06 Yes B Ni(s) Ni (0.75 M) ǁ Ni ( M) Ni(s) 0.06 N C Pt(s) Br ( M) Br (l) ǁ Br (l) Br (1.5 M) Pt(s) 0.07 N 14. What is the cell ptential at 5 C f a cncentratin cell using a standard hydrgen electrde with ne platinum electrde in a ph 7.00 slutin and the ther in ph.00? What is the cell diagram? 0.30 V Pt(s) H (1 atm) H (10 7 M) ǁ H (10 M) H (1 atm) Pt(s) 7

8 xam 4 Wrksheet Answers 15. What cncentratin f ptassium permanganate is need t generate 1.8 V at 5 C when a manganese dixide electrde is placed in this cncentratin f ptassium permanganate and reacting with a manganese electrde in M manganese(ii) chlride? What mass (in mg) f ptassium permanganate is needed t make 10 ml f slutin? 0.1 M 190 mg 16. What mass (in g) f the metals can be depsited using 455 ma f current fr 38 minutes? Cpper frm cpper(ii) sulfate 0.34 g Zinc frm zinc chlride 0.35 g Chrmium frm chrmium(iii) nitrate 0.19 g d. Silver frm silver nitrate 1. g 17. What current (in A) is needed when applied fr 5 min fr each slutin t depsit 0.15 g f the metal? Cpper frm cpper(ii) sulfate 0.5 A Zinc frm zinc chlride 0.5 A Chrmium frm chrmium(iii) nitrate 0.46 A d. Silver frm silver nitrate A 18. Hw lng wuld 1.5 A need t be applied t depsit g f the metal? Cpper frm cpper(ii) sulfate 7.49 min Zinc frm zinc chlride 7.8 min Chrmium frm chrmium(iii) nitrate 13.7 min d. Silver frm silver nitrate.1 min 8