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Answer Keys to Selected Problems

Chapter 19 Key

19.1.  (a) Sc: [Ar]4s23d 1(b)  Ti: [Ar]4s23d 2(c)  Cr: [Ar]4s13d 5(d)  Fe: [Ar]4s23d 6(e)  Ru: [Kr]5s24d 6

 

19.3.  (a)  La: [Xe]6s25d 1La3+: [Xe](b)  Sm: [Xe]6s24f 6,  Sm3+: [Xe]4f 5(c)  Lu: [Xe]6s24f  145d 1Lu3+: [Xe]4f 14

 

19.5.  Al is used because it is the strongest reducing agent and the only option listed that can provide sufficient driving force to convert La(III) into La.

 

19.7.  Mo

 

19.9.  The CaSiO3 slag is less dense than the molten iron, so it can easily be separated. Also, the floating slag layer creates a barrier that prevents the molten iron from exposure to O2, which would oxidize the Fe back to Fe2O3.

 

19.11.  2.57%

 

19.13.  0.167 V

 

19.15E° = −0.6 V, E° is negative so this reduction is not spontaneous. E° = +1.1 V

 

19.17.

(a)  Fe(s) + 2 H3O+(aq) + SO42−(aq) → Fe2+(aq) + SO4​2−(aq) + H2(g) + 2 H2O(l)

(b). FeCl3(aq) + 3 Na+(aq) + 3 OH(aq) →Fe(OH)3(s) + 3 Na+(aq) + 3 Cl(aq)

(c). Mn(OH)2(s) + 2 H3O+(aq) + 2 Br​−(aq) → Mn​2+(aq) + 2 Br​−(aq) + 4 H2O(l

(d). 4 Cr(s) + 3 O2(g) → 2 Cr2O3(s)

(e). Mn2O3(s) + 6 H3O+(aq) + 6 Cl−(aq) → 2 MnCl3(s) + 9 H2O(l)

(f)  Ti(s) + xs F2(g) → TiF4(g)

 

19.19.

(a)  Cr2(SO4)3(aq) + 2 Zn(s) + 2 H3O+(aq) → 2 Zn2+(aq) + H2(g) + 2 H2O(l) + 2 Cr2+(aq) + 3 SO42−(aq)

(b)  4 TiCl3(s) + CrO42−(aq) + 8 H+(aq) → 4 Ti4+(aq) + Cr(s) + 4 H2O(l) + 12 Cl(aq)

(c)  In acid solution between pH 2 and pH 6,  CrO4​2− forms HCrO4​−, which is in equilibrium with dichromate ion. The reaction is 2 HCrO4(aq) → Cr2O72−(aq) + H2O(l).

At other acidic pHs, the reaction is 3 Cr2+(aq) + CrO4​2−(aq) + 8 H3O+(aq) → 4 Cr3+(aq) + 12 H2O(l)

(d)  8 CrO3(s) + 9 Mn(s)  [latex]\xrightarrow {\Delta}[/latex]  4 Cr2O3(s) + 3 Mn3O4(s)

(e)  CrO(s) + 2 H3O+(aq) + 2 NO3​(aq) → Cr2+(aq) + 2 NO3​(aq) + 3 H2O(l)

(f)  CrCl3(s) + 3 NaOH(aq) → Cr(OH)3(s) + 3 Na+(aq) + 3 Cl(aq)

 

19.21.

(a)  3 Fe(s) + 4 H2O(g) → Fe3O4(s) + 4 H2(g)

(b)  3 NaOH(aq) + Fe(NO3)3(aq)  [latex]\xrightarrow {H_2O}[/latex]  Fe(OH)3(s) + 3 Na+(aq) + 3 NO3(aq)

(c)  MnO​4 + 5 Fe2+ + 8 H+ → Mn​2+ + 5 Fe3 + 4 H2O

(d)  Fe(s) + 2 H3O+(aq) + SO42−(aq) → Fe2+(aq) + SO4​2−(aq) + H2(g) + 2 H2O(l)

(e)  4 Fe2+(aq) + O2(g) + 4 HNO3(aq) → 4 Fe3+(aq) + 2 H2O(l) + 4 NO3(aq)

(f)  FeCO3(s) + 2 HClO4(aq) → Fe(ClO4)2(aq) + H2O(l) + CO2(g)

(g)  3 Fe(s) + 2 O2(g)  [latex]\xrightarrow {\Delta}[/latex]  Fe3O4(s)

 

19.23.  As CN is added, Ag+(aq) + CN(aq) → AgCN(s)

As more CN is added,

Ag+(aq) + 2 CN(aq) → [Ag(CN)2](aq)
AgCN(s) + CN(aq) → [Ag(CN)2](aq)

 

19.25.  (a)  Sc3+(b)  Ti4+(c)  V5+(d)  Cr6+(e)  Mn4+(f)  Fe2+ and Fe3+(g)  Co2+ and Co3+(h)  Ni2+(i)  Cu+

 

19.27.  (a)  4, [Zn(OH)4]2−(b)  6, [Pd(CN)6]2−(c)  2, [AuCl2](d)  4, [Pt(NH3)2Cl2](e)  6, K[Cr(NH3)2Cl4](f)  6, [Co(NH3)6][Cr(CN)6](g)  6, [Co(en)2Br2]NO3

 

19.29.

(a)  [Pt(H2O)2Br2]:

image

(b)  [Pt(NH3)(py)(Cl)(Br)]:

image

(c)  [Zn(NH3)3Cl]+ :

image

(d)  [Pt(NH3)3Cl]+ :

image

(e)  [Ni(H2O)4Cl2]:

image

(f)  [Co(C2O4)2Cl2]3−:

image

 

19.31.  (a)  tricarbonatocobaltate (III) ion(b)  tetraaminecopper(II) ion(c)  tetraaminedibromocobalt (III) sulfate(d)  tetraamineplatinum (II) tetrachloroplatinate (II)(e)  tris-(ethylenediamine)chromium (III) nitrate(f)  diaminedibromopalladium(II)(g)  potassium pentachlorocuprate (II)(h)  diaminedichlorozinc (II)

 

19.33.  (a)  none(b)  none(c)  The two Cl ligands can be cis or trans. When they are cis, there will also be an optical isomer.

 

19.35.

image

 

19.37.

image

 

19.39.  [Co(H2O)6]Cl2 with three unpaired electrons.

 

19.41.  (a)  4(b)  2(c)  1(d)  5(e)  0

 

19.43.  (a)  [Fe(CN)6]4−(b)  [Co(NH3)6]3+(c)  [Mn(CN)6]4−

 

19.45.  The complex does not have any unpaired electrons. The complex does not have any geometric isomers, but the mirror image is nonsuperimposable, so it has an optical isomer.

 

19.47.  No. Au+ has a complete 5d sublevel.

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Chapter 19 Key Copyright © by Nicole Bouvier-Brown; Saori Shiraki; J. Ryan Hunt; and Emily Jarvis is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.