EXPERIMENT NO. 9
Separation of Anions by Selective Precipitation Precipitation and Other Selected Reaction Post Lab
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Cl , Br , I , OAc , NO3 , CO3 , C2O4 , 223CrO4 , SO4 , PO4 Part 1: Pr ecipitati on by BaCl 2 2
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CO3 (light yellow ppt), C2O4 223(yellow soln), CrO4 , SO4 , PO4
+ 0.1 M BaCl2
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Cl , Br , I , OAc , NO3
+ 3 M HOAc -
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-, Br , I , OAc ,- NO , CO , C O , 3 3 2 4 COCl PO4 3 223CrO 4 , SO4 , PO4 (basic) (basic)
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C2O4 , CrO4 2(orange ppt), SO4
Part 2: Pr ecipitati on by CaCl CaCl 2 2
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CO3 , C2O4 , CrO4 , 23SO4 , PO4
+ 0.1 M BaCl2
Cl , Br , I , OAc , NO3
+ 0.1 M CaCl2
2-
2-
C2O4 , CO3 , 2- + 3 M HOAc PO4
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SO4 , CrO4 + 3 M HNO3, 0.1 M BaCl2 (yellow soln) CrO4
2-
2-
C2O4
CO3
2-
PO4
3-
SO4
2-
Part 3: Pr ecipitation by AgNO 3 -
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Cl , Br , I , OAc , NO3 , CO3 , C2O4 , 223CrO4 , SO4 , PO4 + 0.1 M BaCl2 -
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CO3 , C2O4 , CrO4 , 23SO4 , PO4
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Cl , Br , I , OAc , NO3
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+ 0.1 M AgNO OAc , 3
NO3 -
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Cl (purple ppt), Br (light + 6 M -NH3 yellow soln, white ppt), I -
Br , I
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Cl , + conc’d NH3
EXPERIMENT NO. 10
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I (green)
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Br (colorless)
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I
Coordination Chemistry Energy is inversely proportional to wavelength; therefore, the color which absorbs highest energy and thus, has the smallest
wavelength, is violet while the color which absorbs the lowest energy and has the longest wavelength is red. -
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I < Br < SCN < Cl < NO3 < F < OH < H2O < C2O4 < NCS < NH3 < en < bipy < phen < NO2 < CN ≈ CO Increasing crystal field strength Post Lab Coordination Compound
Neutral complex At least 1 complex ion Central metal + ligand (2, 3, 4, 5, and 6): dative or coordinate bond 2: Ag(II), Cu(I), Au(I)
ΔO = hc / λ
Part 1: F ormati on of Ni ckel complexes
FORMULA + [Ni(H2O)6] [Ni(en)3] + [Ni(NH3)6] Trend: H2O < NH3 < en
COLOR OF THE SOLUTION Green Purple Blue
COLOR ABSORBED Red Yellow Orange
Part 2: F ormation of Zin c complexes
SOLUTION Zn(NO3)2 + NaOH Zn(NO3)2 + NH3
OBSERVATION Colorless Colorless 3+
2+
IUPAC NAME FORMULA + Tetrahydroxozincate(II) [Zn(OH)4] Tetraamminezincate(II) [Zn(NH3)4]
2+
3+
2+
Part 3: Qual it ative Tests for Cr , Co , Cu , F e , and Ni
QUALITATIVE TEST ADDED + Cr NaOH + H2O2 + Co HOAc + NaNO2 + Cu NH3 + Fe KSCN + Ni Dimethylglyoxime, C4H8O2 N2 Confirmatory Test for Cr
3+
3+
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Cr + 3H2O2 + 10OH 2CrO4 + 8H2O 3+ 2H2O2 is the oxidizing agent (Cr CrO4 ) Tetraoxochromate(VI) – yellow
OBSERVATION Yellow solution Yellow to orange solution Deep blue solution Blood red solution Cherry red precipitate/solution
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Confirmatory Test for Co
2+
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Co + 6NO2 [Co(NO2)6] 4+ 3[Co(NO2)6] + NO2 + 2H [Co(NO2)6] + NO + H2O Hexanitrito-N-cobaltate(III) – yellow to orange
Confirmatory Test for Ni
2+
2+
Bis(dimethylglyoxime)nickel(II) – cherry red 2+ Ni + 2dimethylglyoxime [Ni(DMG)2]
EXPERIMENT NO. 11
RedOx Reactions Pre Lab O
Reduction Potential (E )
Tendency for a specie to be reduced O As E increases, reduction is favored, stronger oxidizing agent O As E decreases, oxidation is favored, stronger reducing agent Zn (-0.76 V) > Fe (-0.44 V) > Cu (0.34 V) O O O E cell = E reduction – E oxidation (must be positive)
Nernst Equation
For non-standard condition O Ecell = E cell – (0.0592 V / 2) log Q
Relationship between E
O
O
O
O
and ΔG
= -nFE F = 96485 coulomb / mol e O O As E increases, ΔG decreases O O As E decreases, ΔG increases ΔG
