Acids covalent compounds

Both boron and aluminium chlorides can be prepared by the direct combination of the elements. Boron trichloride can also be prepared by passing chlorine gas over a strongly heated mixture of boron trioxide and carbon. Like boron trifluoride, this is a covalent compound and a gas at ordinary temperature and pressure (boiling point 285 K). It reacts vigorously with water, the mechanism probably involving initial co-ordination of a water molecule (p, 152). and hydrochloric acid is obtained ... 

In its chemistry, cadmium exhibits exclusively the oxidation state + 2 in both ionic and covalent compounds. The hydroxide is soluble in acids to give cadmium(II) salts, and slightly soluble in concentrated alkali where hydroxocadmiates are probably formed it is therefore slightly amphoteric. It is also soluble in ammonia to give ammines, for example Of the halides, cadmium-... 

Lewis acids are defined as molecules that act as electron-pair acceptors. The proton is an important special case, but many other species can play an important role in the catalysis of organic reactions. The most important in organic reactions are metal cations and covalent compounds of metals. Metal cations that play prominent roles as catalysts include the alkali-metal monocations Li+, Na+, K+, Cs+, and Rb+, divalent ions such as Mg +, Ca +, and Zn, marry of the transition-metal cations, and certain lanthanides. The most commonly employed of the covalent compounds include boron trifluoride, aluminum chloride, titanium tetrachloride, and tin tetrachloride. Various other derivatives of boron, aluminum, and titanium also are employed as Lewis acid catalysts. 

The elements show increasing metallic character down the group (Table 14.6). Carbon has definite nonmetallic properties it forms covalent compounds with nonmetals and ionic compounds with metals. The oxides of carbon and silicon are acidic. Germanium is a typical metalloid in that it exhibits metallic or nonmetallic properties according to the other element present in the compound. Tin and, even more so, lead have definite metallic properties. However, even though tin is classified as a metal, it is not far from the metalloids in the periodic table, and it does have some amphoteric properties. For example, tin reacts with both hot concentrated hydrochloric acid and hot alkali ... 

The question as to whether or not hydrazoic add and nitric add are more closely related to the corresponding covalent compounds than to the ions could be answered by determining the configurations of the acids. From general information we would predict that the H-N and H-0 bonds are essentially covalent (with perhaps about one-third ionic character) and that the Ns and NOs groups in the acids have the same structures as in methyl azide and nitrates. This prediction is supported by the instability of the acids. 

In each case the mechanism involves generation of an aryl radical from a covalent azo compound. In acid solution diazonium salts are ionic and their reactions are polar. When they cleave, the product is an aryl cation (see p. 852). However, in neutral or basic solution, diazonium ions are converted to covalent compounds, and these cleave to give free radicals ... 

Apart from the three broad categories of student conceptions discussed above, students displayed several inappropriate conceptions relating to the stractural properties of substances. For example, 14% of students suggested that Mg + ions were present in magnesium ribbon. A second example involved the chemical reaction between copper(II) oxide powder and dilute sulphuric acid. In this instance, 25% of students suggested that Cu + ions were present only in aqueous solution but not in the solid and liquid states. This view was rather unexpected because students had earlier been introdnced to ionic and covalent compounds. It is likely that students had merely rote-learned the general rale without sufficient understanding that ionic solids are formed between metallic and non-metallic elements. 

H3 PO4 Phosphoric acid is a covalent compound with a net charge of zero. Each hydrogen atom has an oxidation number of+1 (Guideline 3), and each oxygen has an oxidation number of-2 (Guideline 4). Now add the contributions from these atoms 3(+l) + 4(-2) = -5. For the oxidation numbers to sum to zero (Guideline 2), the phosphorus atom of phosphoric acid must have an oxidation number of +5. 

COVALENT COMPOUNDS, METAL IONS OXIDATION-REDUCTION acid, viz. 

Thorn K A, KR Kennedy (2002) N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose. Environ Sci Technol 36 3787-3796. 

In the first reaction, two ionic compounds in water are mixed. The AgCl formed by the swapping of anions is insoluble, causing the reaction to proceed. The solid AgCl formed from solution is an example of a precipitate. In the second reaction, a covalent compound, HzO, is formed from its ions in solution, H+ and OH, causing the reaction to proceed. In the third reaction, a solid reacts with the acid in solution to produce two covalent compounds. 

Most of the numerous and frequent hazards experienced with perchloric acid have been associated with either its exceptional oxidising power or the inherent instability of its covalent compounds, some of which form readily. Although the 70-72% acid of commerce behaves when cold as a very strong, but non-oxidising acid, it becomes an extreme oxidant and powerful dehydrator at elevated temperatures (160°C) or when anhydrous [1],... 

In many ways, TiCl4 behaves as a covalent compound of a nonmetal. It is a strong Lewis acid that forms complexes with many types of Lewis bases, and it hydrolyzes in water. It also reacts with alcohols to yield compounds having the formula Ti(OR)4. However, it is the behavior of TiCl4 (reacting with [A1(C2H5)3]2) as a catalyst in the Ziegler-Natta polymerization of ethylene that is the most important use of the compound (see Chapter 22). 

B Since acetic acid is a weak acid, it is not dissociated completely in aqueous solution (except at infinite dilution) it is misleading to write it in ionic form. The products of this reaction are the gas carbon dioxide, the covalent compound water, and the ionic solute calcium acetate. Only the latter exists as ions in aqueous solution. 

In accord with the high acidities of HOSeF5 and HOTeFs, acid displacement reactions are frequently performed, affording ionic as well as covalent compounds as inEqs. (16)—(18). For the preparation of al-koxopentafluoroorthotellurates, a method that is widely applied is the reaction of the respective alcohol with TeFg (Section V,A,2). 

Compounds like alcohols are nonelectrolytes—substances than do not conduct an electrical current when dissolved in water. However, certain covalent compounds, like acids, will ionize in water, that is, form ions ... 

As mentioned before, certain covalent compounds, like alcohols, readily dissolve in water because they are polar. Since water is polar, and these covalent compounds are also polar, water will act as a solvent for them (general rule of solubility Like dissolves like ). Compounds like alcohols are nonelectrolytes—substances that do not conduct an electrical current when dissolved in water. However, certain covalent compounds, like acids, will ionize in water, that is, form ions ... 

Acids react with HgO to produce corresponding Hg(II) compounds. Two classes of Hg(II) compounds maybe defined covalent and ionic. The covalent compounds HgCl2, HgBr2, HgD, and Hg(CN)2 go into HOH solution chiefly as undissociated molecules, which undergo little hydrolysis. The ionic compounds which include HgF2, Hg(N03)2, HgS04, and Hg(C104)2 go into... 

Every syllable in the name of a chemical compound conveys something about that compound. From ionic and molecular (covalent) compounds to organic hydrocarbons and acids, the names matter, and you find out why in this part. 

Covalent compounds generally have higher vapor pressure than ionic compounds. The fishy smell of fish arises from amines in the fish. Explain why squeezing lemon (which is acidic) onto fish reduces the fishy smell (and taste). 

Hydrazotc acid, HN,. ply.. = 4.72, and most of its covalent compounds (including its heavy metal salts) are explosive. It is formed (1) in 90% yield by reaction of sodium amide with nitrous oxide, (2) by reaction of hydraztntum ion with nitrous acid, (3) by oxidation of hydrazimum salts, (4) by reactio n of hydt azinium hydrate with nitrogen trichloride tin benzene solution). Hvdrazoic acid forms metal azides with the corresponding hydroxides and carbonates. It reacts with HC1 to give ammonium chlonde and nitrogen, with H2SO4 to form hydrazinium acid solfate, with benzene to form aniline, and it enters into a number of oxidation-reduction reactions. 

The elements show increasing metallic character down the group (Table 14.12). Carbon has definite nonmetallic properties it forms covalent compounds with nonmetals and ionic compounds with metals. The oxides of carbon and silicon are acidic. Germanium is a typical metalloid... 

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