9answers - Homework#9 1 The oxalate ion is a a b c d e...

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Homework #9 1. The oxalate ion is a a. monodentate ligand. b. bidentate ligand. c. tridentate ligand. d. tetradentate ligand. e. will not act as a metal ligand. ANS: B The oxalate ion is a bidentate ligand which means it bonds via 2 coordination sites to a metal as shown below. All 4 oxygens cannot bond to a single metal because the oxalate ion is planar. O - O O O - M 2. What is the oxidation state of Cr in Cr(CO) 6 ? a. 0 b. + 1 c. + 3 d. + 6 e. –6 ANS: A CO (carbon monoxide) is a neutral ligand (has no charge) and coordinates to the metal via dative bonds. Therefore, Cr(CO) 6 has 6 neutral ligands making the charge on the Cr zero. 3. What is the chemical formula of pentaamminechloroplatinum(IV) bromide? a. [Pt(NH 3 ) 5 Cl]Br b. [Pt(NH 3 ) 5 ]ClBr c. [Pt 5 (NH 3 )Cl]Br d. [Pt(NH 3 ) 5 Cl]Br 3 e. [Pt 2 (NH 3 ) 5 Cl]Br ANS: D
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To determine the chemical formula of pentaamminechloroplatinum(IV) bromide, we look at each part and then combine to find the whole formula. “Pentaamine” indicates that 5 ammonia groups are coordinated to the metal. Chloro tells us that one chloro group (Cl - ) is bonded to the metal. The ammonia groups are neutral ligands but the chloro group is a -1 ligand so this accounts for 1 of the positive charges on the metal. However, we see from the name that the oxidation state of the metal is +4 from (IV). Therefore, we need to balance this charge in order to make the whole species neutral. We can conclude therefore that we need 3 Br as outer sphere counter ions. Therefore, the answer is D. 4. Which is the most descriptive name the following compound, [Pt(H 2 NCH 2 CH 2 NH 2 )Cl 4 ]Cl 2 a. hexachloro(ethylenediamine)platinum (IV) b. hexachloride(ethylenediamine)platinum (VI) c. tetrachloro(ethylenediamine)platinum (IV) chloride d. tetrachloro(ethylenediamine)platinum (VI) chloride e. Platinum(ethylenediamine)hexachloride ANS: D This problem is the opposite of problem 3. First, we see that the platinum is coordinated to one ethylenediamine and 4 chloro ligands (tetrachloro). The oxidation state of the platinum is +6 to balance the charge of the 6 Cl groups (four are coordinated directly to the Pt and two are counterions). Therefore, the oxidation state of the platinum is +6 which is represented by (VI) making the answer D. 5. What is the chemical formula of potassium hexafluorocobaltate(III)? a. [CoK]F 6 b. K[CoF 6 ] c. K[CoF 6 ] 3 d. K 3 [CoF 6 ] e. K[Co 3 F 6 ] ANS: D Hexafluoro means we have 6 fluoro groups which is 6 F- ions coordinated to a cobalt. In the problem, we are told that the oxidation state of the metal is +3 (i.e. III) but the 6 F- ions have a charge of -6. Therefore, we need counter ions that have a charge of +3. Therefore, we use three +1 potassium ions to balance the charge. 6. How many isomers are there of the triamminetriaquachromium (III) ion (octahedral)? a. 1 b. 2 c. 3 d. 4 e. 6 ANS: B In the triamminetriaquachromium (III) ion, we have 3 NH 3 ligands on the metal and 3H 2 O ligands on the metal. 6 ligands on a metal creates on octahedral geometry. There are only two different ways these ligands can be arranged and these are called facial and meridional,
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as shown below.
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9answers - Homework#9 1 The oxalate ion is a a b c d e...

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