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General Chemistry Principles, Patterns, and Applications, 2011

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. a. WO 3 ( s) + 3C ( s) + 3Cl 2 ( g) - ® D WCl 6 ( s) + 3CO( g)Sc 2O 3(s) + 2OH − (aq) + 3H 2O(l)<br />

→ 2[Sc(OH) 4] − (aq)<br />

c. 2KMnO 4(aq) + 2H 2SO 4(l) → Mn 2O 7(l) + 2KHSO 4(soln) + H 2O(soln)<br />

d. 4CrCl 2(aq) + O 2(g) + 4H + (aq) → 4Cr 3+ (aq) + 8Cl − (aq) + 2H 2O(l)<br />

Given: balanced chemical equation<br />

Asked for: why the indicated products form<br />

Strategy:<br />

Refer to the periodic trends in this section, Figure 23.1 "The Metallic Radii of the First-, Second-, <strong>and</strong> Third-<br />

Row Transition Metals", Figure 23.2 "Some Trends in Properties of the Transition Metals", Figure 7.11 "First<br />

Ionization Energies of the ", Table 23.1 "Valence Electron Configurations of the First-Row Transition<br />

Metals", Table 23.2,Table 23.3 "Common Oxidation States of the First-Row Transition Metals*", Table 23.4<br />

"Some Properties of the Elements of Groups 3, 4, <strong>and</strong> 5", Table 23.5 "Some Properties of the Elements of<br />

Groups 6 <strong>and</strong> 7", Table 23.6 "Some Properties of the Elements of Groups 8, 9, <strong>and</strong> 10", <strong>and</strong> Table 23.7 "Some<br />

Properties of the Elements of Groups 11 <strong>and</strong> 12" to explain why these products form.<br />

Solution:<br />

a. The most stable oxidation state for Ti is +4, <strong>and</strong> neither reactant is a particularly<br />

strong oxidant or reductant; hence a redox reaction is unlikely. Similarly, neither<br />

reactant is a particularly strong acid or base, so an acid–base reaction is unlikely.<br />

Because TiCl 4 contains Ti in a relatively high oxidation state (+4), however, it is likely<br />

to be rather covalent in character, with reactivity similar to that of a semimetal<br />

halide such as SiCl 4. Covalent halides tend to hydrolyze in water to produce the<br />

hydrohalic acid <strong>and</strong> either the oxide of the other element or a species analogous to<br />

an oxoacid.<br />

b. This reaction involves the oxide of a group 6 metal in its highest oxidation state<br />

(WO 3) <strong>and</strong> two elements, one of which is a reductant (C) <strong>and</strong> the other an oxidant<br />

(Cl 2). Consequently, some sort of redox reaction will occur. Carbon can certainly<br />

react with chlorine to form CCl 4, <strong>and</strong> WO 3 is a potential source of oxygen atoms that<br />

can react with carbon to produce CO, which is very stable. If CO is one of the<br />

products, then it seems likely that the other product will contain the metal <strong>and</strong><br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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