INORGANIC CHEMISTRY CHEM 312
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This 5 page Study Guide was uploaded by Carmela Kilback on Wednesday September 9, 2015. The Study Guide belongs to CHEM 312 at University of Washington taught by Josephus Norman in Fall. Since its upload, it has received 51 views. For similar materials see /class/192540/chem-312-university-of-washington in Chemistry at University of Washington.
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Date Created: 09/09/15
Chem 312 N W U ANSWERS TO STUDY QUESTIONS REDOX Prof Norman a Oxidation H3P03aq 3 H200 gt HEPOgaq 2 H30aq 2e 800x 028 J quot 2 HEOYaq 2e gt Hlg 2 H208 gored 000 Hence Soredox Sooxida m Soredumm 028 V 3 reaction spontaneous b The fallcell reaction equation contains no H30 or OH hence 6nd is not pHdependent Another way of saying this is that the pH dependence of both halfcell potentials is the same note the presence of equal quantities of H3O in the 2 equations c Oxidation P in H3P03 a P in H3PO4 Reduction 2 H in H20 a 2 Hquot in H2 As shown on coursepack page 13 0 Sredumm for H20 increases by 041 V 00591 X 7 from pH 14 to pH 7 0 Sredumm for 02 decreases by 041 V from pH 0 to pH 7 Hence at pH 7 0 the strongweak reductant boundary is at 082 041 041 V 0 the strongweak oxidant boundary is at 123 041 0 82 V Note that Sredumon for any species with H 30 in its halfcell equation also decreases from pH 0 to pH 7 by 041az V Hence the category of such a species strong or weak may or may not change from pH 0 to pH 7 depending on its value of az Soredumm 133 and 125 V for Cr2072 and N037 respectively 133 00591146pH 133 0138pH for Cr2072 Eredumm 125 005911210pH 125 0071pH for N037 3 the two potentials cross when 133 0138pH 125 0071pH 3 pH 119 From page 12 At pH 0 8reduction From page 13 a Sright glen 062 006 gt 0 for U hence UH disproportionates by the reaction 2UOoHoO aq 4HOaq a Uoomoow zYaq UHzO 4 4Hzoa F Uozailongaq 4HEOaq 6e a Us 12 HOf 51mm 006 062 061 31806 4189 V UH204aq 4e gt Um 8HOf 51mm 061 31804 150 V The formulas are predicted from the oxidation states summarized on page 16 with 0 uorides taking highest common and chlorides most common in the d block 0 careful attention to where the lower and higher oxidation states are stable in the I block Can CaCIz VF 5 VCI4 ReF7 ReCI4 TEF TICK SiF4 SiCI4 SF 6 SCI4 a 032 2NaIaq 2H30aq a 022 12m 2Naaq 3 HZOU Soredox 207 054 153 V b 2Afs 3 FeNOlaq 6H20f gt AEHO 3aq 6N0 aq 3 Fes Soredox 166 044 122 V c Crgs MnBrggag gt no reaction since Soredox 074 119 045 V d 3 Cus Kgcigoaq 14 HEOYaq 9Hzom gt 3 C11HO 2aq 2 CrHO 3aq 2Kaq 816m 015133 118 V Chemistry 312 N E 4 UI 05 gt1 Professor Norman STUDY QUESTIONS MOLECULAR SYMMETRY A molecule with an S 5 axis necessarily has at least how many symmetry operations List all of them in their simplest form showing their relationship to the S 5 axis What point group has this as its complete set of operations Determine the point group of each of the following molecules The gure and page references are from your text a Benzene C5H5 Fig 35 p 76 f CoH54 Fig 910a p 216 b Benzene135C02H Box 93 p 212 g CoNH35Cf2 Fig 2124 p 517 Ignore H atoms c Formic acid dimer Fig 95b p 211 h Rengi Fig 910c p 216 d Diborane B2H5 Fig 121 p 253 i Os03NT Fig 2237 p 559 e CEF3 Fig 130a p 46 j PdsCfiz Fig 2263 p 573 Consider the dxy orbital on the central atom of a molecule with C4 symmetry Assume that the C4 axis is along the Cartesian direction See Fig 111 text page 14 for a picture ofthe sign of the dxy orbital in different quadrants of space Show why the dxy orbital belongs to the Bg representation of C411 Hint draw pictures of how the orbital looks after each symmetry operation of C411 Consider C6H62Cr depicted in Fig 2356 on text page 616 What is its point group How many different energies will there be for the molecular orbitals that correspond most closely to the Cr valence atomic orbitals The trigonalplanar molecule Ang has D3 symmetry Assume that the C3 axis is along The hydrogen s orbitals form SALCs belonging to the representations A1 E 39 Which aluminum valence orbitals will be nonbonding in the molecule Determine the following directproduct representations a D211 Blg X Au D511 A2 X A2 C Td A2 X T1 Consider the MO diagram for Con547 on coursepack page 35 The complex CoCN54 has only one unpaired electron CN bonds to dblock metals analogously to CO Explain the decrease in paramagnetism between Con54 and CoCN54 iTi lbz 13 The highest occupied MOs of FeSR4T the active site of oxidized iTi 1b1 14 1F e ironsulfur proteins are shown at left along with their energies in sunbeamswoodstovez The point group is CZV 7T 2a1 16 a What is the standard symbol for the ground state of FeSR4T 7T 2a 20 7T 1a1 23 b What are the 3 lowestenergy allowed electronic transitions of FeSR4T Along what Cartesian directions are they allowed jig 1a 27 Chemistry 312 N E 4 V39 0 gt1 9 50 Professor Norman STUDY QUESTIONS ACIDS AND BASES Consider 01M aqueous solutions of the compounds listed below Write X in the column that gives the correct pH of each solution Write the dominant reaction leading to that pH in the space to the right use gt for complete and for incomplete reactions pH 1 17 713 13 V 1 r Dominant Reaction HI NaHCrO4 FeSO4 NH42HPO4 KZS Explain the periodic trends in bond energy Elm for binary hydrides shown on coursepack page 6 Hint what other atomic property decreases as Ebond increases Coursepack page 4 lists pKa values for removal of each successive Hl in acids such as H2804 H3PO4 H2C03 etc Why is only one pKa value listed for boric and silicic acids What is ApKaH2C03 H C037 Why does the value not fit very well Rule 4 on coursepack page 8 Which acid pair listed under Rule 4 probably ts the rule only accidentally Are HCEOZ and HCEO3 weak or strong acids Why Explain why the form of aqueous metal ions varies with pH as described in statements 3 and 4 on coursepack page 9 Estimate the pKa of NazHPO4am Consider acidbase chemistry in H 2Sf Note that pKaH3S cs 5 Classify the following as weak or strong acids or bases in HZSU HCEO4 H2804 H3PO4 H4SiO4 Complete and balance the following reactions Include phases of products a B2H5g HZOU gt b MgHzs HzSO4f gt c CH3Liether NH3E gt d HBrg NaSHs gt e PbOs HOAcaq gt Chem 312 4 V39 gt1 ANSWERS TO STUDY QUESTIONS SYMMETRY Prof Norman S n odd generates 2n operations 3 85 generates 10 operations as follows 5 52 C52 853 54 C54 855 5h 856 C5 857 58 C53 859 510 E Reordered these are E C5 C52 C53 C54 7 S5 S53 S55 S57 S59 7 the operations of C5h a D511 C Czh e CZV g C4v C3v b C311 d D211 f C4V h D311 j D411 If is toward the right and y toward the top the sign behavior of dxy in the four quadrants of the xy plane is shown at left The C4 axis perpendicular to the xy plane rotates dxy 90 and hence changes all the signs Consistently xC4 l in the BIg ir of C411 Similarly Czdxy dxy and xCz l in Bg idxy dxy and xi l in Bg etc For all operations of C411 the Bg characters describe correctly the effect of the corresponding symmetry operations on dxy Point group is Dgh for which the character table shows the following correspondence of centralatom that is Cr valence orbitals to ir Alg s and dzz Am pz E1 px py pair Elg dxz dyz Ezg dxzeyz dxy pairs Two orbitals that as a pair form a basis for a two dimensional ir are degenerate in energy Hence the MOs most like the Cr 3d 4s and 4p valence orbitals will have six different energies in C5H52Cr encompassing two Alg and one A2J MOs plus one Eu one Elg and one Ezg degenerate pairs of MOs In D311 the centralAf atom valence orbitals belong to A139 s A2 pz and E39 px py pair Hence the AE s and px py orbitals can overlap with 3Hatom SALCs to form MOs The AI pz orbital does not belong to the ir of any 3H SALC hence it is nonbonding a Blu A1 0 T2 Moving from a TD donor ligand Cf to a TEacceptor ligand CNT will increase A0 the energy difference between the 2tg and 3eg dlike orbitals Apparently in CoCN54T A0 has become large enough so that it is more favorable to expend the energy needed to pair the 6th dlike electron in the 2tg orbital rather than raise its energy by A0 and keep it unpaired in 3eg a Ground state symbol 6A1 since S 52 3 281 6 and a1gtlt a X a1gtltb1gtltbz A1 b The only spinallowed transitions originate in the laz orbital since others require a change in total spin In CzV transitions belonging to A1 B1 and B2 are symmetryallowed along g and y respectively Hence the following transitions in FeSR4T are fully allowed 1a 6 2a that is 6A1 a 6A1 direct product A1 allowed AE hV 0 7sw2 1a 9 1b that is 6A1 a 632 direct product B2 allowedx AE hV 13 swz 1a 9 lb that is 6A1 a 631 direct product B1 allowed J AE hV 14 swz The other 2 transitions from laz lead to A2 direct products and hence are forbidden
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