Chlorides oxidation numbers

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the state(s) of oxidation, eg, titanium(II) chloride for TiCl2, iron(II) oxide for FeO, titanium(III) chloride for TiCl, iron(III) oxide for Fe203, titanium(IV) chloride for TiCl, and iron(II,III) oxide for Fe O. In this system, only the termination -ate is used for anions, followed by Roman numerals in parentheses. Examples are potassium manganate(IV) for K2Mn02, potassium tetrachloroplatinate(II) for K PtCl, and sodium hexacyanoferrate(III) for Na3Fe(CN)3. Thus a set of prefixes and terminations becomes uimecessary. 

An ionic compound is named with the cation name first, followed by the name of the anion the word ion is omitted in each case. The oxidation number of the cation is given if more than one charge is possible. However, if the cation comes from an element that exists in only one charge state (as listed in Fig. C.6), then the oxidation number is omitted. Typical names include potassium chloride (KC1), a compound containing K+ and Cl" ions and ammonium nitrate (NH4NOs), which contains NH4+ and NO3" ions. The cobalt chloride that contains Co2+ ions (CoCl,) is called cobalt(II) chloride C0CI3 contains Co3+ ions and is called cobalt(III) chloride. 

When a ruthenium chloride solution was electrolyzed for 500 s with a 120-mA current, 31.0 mg of ruthenium was deposited. What is the oxidation number of ruthenium in the ruthenium chloride ... 

In chloride ions, Cl-, the oxidation number of Cl = -1 (chlorine has been reduced from 0 to -1)... 

The development of G. N. Lewis s octet rule for the s/p-block elements was strongly influenced by the stoichiometric ratios of atoms found in the common compounds and elemental forms (CH4, CCI4, CO2, CI2, etc.). Let us therefore begin analogously by examining the formulas of the common neutral binary chloride, oxide, and alkyl compounds of transition metals. (Here we substitute alkyl groups for hydrogen because only a small number of binary metal hydrides have been well characterized.)... 

Table 4.1. Most commona ML compounds (L = chloride, oxide, alkyl) and number of unpaired electrons1 (eu) for group 3-12 transition metals M asterisks...

It may appear strange that the term reduction is associated with a gaining process. Actually, the term reduction was coined as a result of what happens to the oxidation number of the element when the electron transfer takes place. The oxidation number of an element is a number representing the state of the element with respect to the number of electrons the element has given up, taken on, or contributed to a covalent bond. For example, pure sodium metal has neither given up, taken on, nor shared electrons, and thus its oxidation number is zero. In sodium chloride, however, the sodium has given up an electron and becomes a +1 charge thus its oxidation number is +1. The chlorine in NaCl has taken on an electron... 

Grey potassium metal, which is stored under oil, reacts very vigorously with greenish-yellow chlorine gas to form white potassium chloride. The changes in oxidation numbers show that this synthesis reaction is also a redox reaction. 

The oxidation number of chlorine decreases, so perchlorate ions are reduced to chloride ions. 

The oxidation state is similar to the valency that an element has when it is part of a compound. For example, in Iron(ll) chloride we might say that the iron has a valency of 2. However, it is actually more accurate to say that iron is in oxidation state (11) or has oxidation number +2. 

Dihalogenation of oxindole followed by alkaline hydrolysis of the 3,3-dihalooxindole has been applied to the synthesis of some isa-tins.66,126,136 137b A number of oxindoles have been treated with nitrous acid to give isatin-3-oximes.100,138 Reduction of the oximes to 3-aminooxindoles followed by ferric chloride oxidation gave isatins.100,138 When this sequence was applied to 7-azaoxindole, the azaisatin 33 was... 

Solution Consider the fate of each reactant separately K2Cr207 produces Cr3+ ions FeCl2 produces Fe3+ ions. No changes to the potassium or chloride ions are mentioned, so we assume they are spectator ions. The oxidation number, x, of chromium in the Cr2072- ion is calculated from... 

Now we can work out the formula of an ionic compound formed between the monatomic ions of two main-group elements, one a metal and the other a nonmetal. Unless a lower oxidation number is specified (as for the p-block metals), the metal atom loses all its valence electrons, and the nonmetal atom gains enough electrons to complete its valence shell. Then we adjust the numbers of cations and anions so that the resulting compound is electrically neutral. A simple example is calcium chloride. The calcium atoms ([Ar]4s2) each lose two electrons, to form... 

Halides of metals tend to be ionic unless the metal has an oxidation number greater than +2. For example, sodium chloride and copper(II) chloride are ionic compounds and have high melting points, but TiCl4 and FeCl3 sublime as molecules. 

EXAMPLE 1 CdCl2 is an ionic compound and may be designated as Cd2+(C1 (2 to show its ionic character. The cadmium and chloride ions possess oxidation numbers +2 and — 1, as this is an ionic compound there is no sharing of electrons... 

Monatomic ions have an oxidation number equal to the charge of the ion. Thus, a sodium ion, Na+, has an oxidation number of +1 that of chlorine in a chloride ion, Cl-, is —1. 

Notice in the balanced equation that two moles of Na were used to react with the two moles of chlorine atoms in one mole of Cl2. Each mole of Na lost one mole of electrons each mole of chlorine atoms gained a mole of electrons. Two moles of electrons were transferred to form two moles of NaCl. The overall reaction is the sum of the two half-reactions the moles of electrons cancel, and the sodium ions and chloride ions combine to form sodium chloride. Note that the sum of the oxidation numbers in sodium chloride is zero (+1) + (—1) = 0. 

Oxidation-reduction reactions, even complex ones, can be balanced using either the half-reaction method or the oxidation number method. The half-reaction method will be discussed first, using the reaction of iron with chlorine to produce iron chloride. 

Fig Proposed mechanism for the oxidation of ethylene to acetaldehyde in the Wacker process. Chloride ligands have been omitted. The oxidation number ofpalladium is + 2 at all stages of this cycle except the upper left where eductive elimination of acetaldehyde gives Pd (0), which is oxidised by Cu (II). The complete cycle for the reoxidation of Cu (I) is not shown. 

These redox reactions, in which oxygen transfer occurs, involve changes of two units in the oxidation numbers of reactant and product. One-electron redox reactions may occur with the transfer of a halogen. The reaction between Cr+2 and Fe 3, for example, is strongly catalyzed by added chloride ion and when chloride is added to the reaction mixture, the resultant Cr(III) is present as (BUO CrC 2. It might be suggested that Cl becomes attached to Cr+a after the redox has occurred, but this cannot be. In the first place, independent experiments show that under these conditions the reaction between Cr+3 and Cl is very slow second, chloride attachment after the redox has occurred would not explain the catalytic role of chloride. It is more likely that the reaction occurs via a chloride-bridge transition state, and that the redox is accomplished by a chlorine transfer ... 

When determining which substances were oxidized and reduced in a redox reaction, first assign the oxidation numbers to all the elements in the reaction. The formation for magnesium chloride serves as an example ... 

B Because they have an oxidation number of 2+ when they form ions, the alkaline earth metals (elements in group 2) will take on two chlorine ions to form chloride salts. 

Tin(II) chloride SnCl2 Tin(II) ions are strong reducing agents. When oxidized to tin(IV) the oxidation number of tin increases from +2 to +4, corresponding to the release of 2 electrons ... 

Note that the oxidation number of copper in the solution is +1. The test is best carried out on filter paper or drop-reaction paper and is applicable in the presence of chlorides, bromides, iodides, hexacyanoferrate(II) and (III) ions. 

A closer relationship between foam stability and HLB has been reported for two- or three-phase systems surfactant solution-oil or oil-surfactant phase-water [60,109-111]. The effect of various parameters changing HLB on the stability of foams and emulsions has been studied in [111]. These were the concentration of amyl alcohol and sodium chloride, the number of the ethylene oxide groups in the molecule of the oxyethylated octylphenol. As a general parameter of HLB the authors used the surfactant affinity difference concept (SAD) which is an empirical generalised formulation. It measures the deviation from the optimum formulation for three phase behaviour. For anionic surfactants... 

In Chapter 5, we learned to write formulas for ionic compounds from the charges on the ions and to recognize the ions from the formulas of the compounds. For example, we know that aluminum chloride is AICI3 and that VCI2 contains ions. We cannot make comparable deductions for covalent compounds because they have no ions there are no charges to balance. To make similar predictions for species with covalent bonds, we need to use the concept of oxidation number, also called oxidation state. A system with some arbitrary rules allows us to predict formulas for covalent compounds from the positions of the elements in the periodic table and also to balance equations for complicated oxidation-reduction reactions. 

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