The interaction of fluorine with water equation. The reactivity of halogen

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The hydrogen atom has an electronic formula of external (and only) electronic level 1 s. one . On the one hand, according to the presence of one electron at the outer electron level, the hydrogen atom is similar to alkali metal atoms. However, he, as well as halogens, not enough to fill out the external electronic level of just one electron, since no more than 2 electrons can be located at the first electron level. It turns out that hydrogen can be placed simultaneously both in the first and in the penultimate (seventh) group of the Mendeleev table, which is sometimes done in various variants of the periodic system:

From the point of view of hydrogen properties as a simple substance, it, nevertheless, has more in common with halogens. Hydrogen, as well as halogens, is non-metal and forms the dimensional molecules (H 2).

Under normal conditions, hydrogen is a gaseous, a low-active substance. The low activity of hydrogen is due to the high strength of the connection between hydrogen atoms in the molecule, for the breaking of which is required or strong heating, or the use of catalysts, or both at the same time.

The interaction of hydrogen with simple substances

with metals

Metals hydrogen reacts only with alkaline and alkaline earth! Alkaline metals include metals of the main subgroup of the I-th group (Li, Na, K, Rb, CS, FR), and to alkaline-land - metals of the main subgroup of the II group, except beryllium and magnesium (CA, SR, BA, RA)

When interacting with active metals, hydrogen exhibits oxidative properties, i.e. Lowings its degree of oxidation. At the same time, hydrides of alkaline and alkaline earth metals, which have an ion structure are formed. The reaction occurs when heated:

It should be noted that the interaction with active metals is the only case when molecular hydrogen H 2 is an oxidizing agent.

with non-metals

From non-metals hydrogen reacts only with carbon, nitrogen, oxygen, gray, selenium and halogens!

Under the carbon, graphite or amorphous carbon should be understood, since the diamond is an extremely inert allotropic carbon modification.

When interacting with non-metals, hydrogen can only perform the reducing agent function, that is, only increase its degree of oxidation:

The interaction of hydrogen with complex substances

with metals oxides

Hydrogen does not react with metal oxides that are in a row of metal activity to aluminum (inclusive), however, it is able to restore many metal oxides to the right of aluminum when heated:

with non-metal oxides

From non-metal oxides, hydrogen reacts when heated with nitrogen oxides, halogen and carbon. Of all the interactions of hydrogen with non-metal oxides, it should be noted its reaction with carbon monoxide CO.

A mixture of CO and H 2 even has its own name - "Synthesis gas", because of it, depending on the conditions, such popular products of industry as methanol, formaldehyde, and even synthetic hydrocarbons can be obtained:

c acids

With inorganic acids, hydrogen does not react!

From organic acids, hydrogen reacts only with unsaturated, as well as with acids containing functional groups capable of restoration of hydrogen, in particular aldehyde, keto- or nitro groups.

c salts

In the case of aqueous solutions of salts, their interaction with hydrogen does not flow. However, when hydrogen passes over solid salts of certain metals of medium and low activity, their partial or complete recovery is possible, for example:

Chemical properties of halogen

Halogens are called the chemical elements of the group VIIA (F, CL, BR, I, AT), as well as simple substances formed by them. Hereinafter, in the text, if it is not said, it will be simple substances under halogens.

All halogens have a molecular structure, which causes low melting and boiling points of these substances. Halogen molecules Di-Town, i.e. Their formula can be written in general as Hal 2.

It should be noted such a specific physical property of iodine, as its ability to sublimation or, in other words, retreat. Retreat, Called a phenomenon in which the substance in the solid state is not melted during heating, and, by passing the liquid phase, immediately goes into a gaseous state.

The electronic structure of the external energy level of the atom of any halogen has the form of NS 2 NP 5, where n is the period number of the periodleeva table, in which the halogen is located. As you can see, up to the eight-electron outer sheath atoms of halogen lacks only one electron. It is logical to assume mainly the oxidizing properties of free halogen, which is confirmed in practice. As is known, the electronegability of non-metals when driving down the subgroup decreases, and therefore the activity of halogen decreases in a row:

F 2\u003e Cl 2\u003e br 2\u003e i 2

The interaction of halogens with simple substances

All halogens are highly active substances and react with most simple substances. However, it should be noted that fluorine due to its extremely high reactivity can respond even with those simple substances with which the remaining halogens cannot react. Such simple substances include oxygen, carbon (diamond), nitrogen, platinum, gold and some noble gases (xenon and crypton). Those. actually, fluoro does not react only with some noble gases.

The remaining halogens, i.e. Chlorine, bromine and iodine, are also active substances, but less active than fluorine. They react practically with all the simple substances, except for oxygen, nitrogen, carbon in the form of diamond, platinum, gold and noble gases.

Interaction of halogens with non-metals

hydrogen

When the interaction of all halogen with hydrogen is formed halogen breeding With the general formula of Hhal. At the same time, the fluorine reaction with hydrogen begins spontaneously even in the dark and flows with an explosion in accordance with the equation:

The reaction of hydrogen chlorine can be initiated by intense ultraviolet irradiation or heating. Also flows with an explosion:

Bromine and iodine react with hydrogen only when heated and at the same time, the reaction with iodine is reversible:

phosphorus

The interaction of fluorine with phosphorus leads to the oxidation of phosphorus to the highest oxidation (+5). In this case, the formation of phosphorus pentafluoride:

In the interaction of chlorine and bromine with phosphorus, it is possible to obtain phosphorous halides as to the degree of oxidation + 3 and in the degree of oxidation +5, which depends on the proportions of the reacting substances:

In this case, in the case of white phosphorus in the fluorine atmosphere, chlorine or liquid bromine, the reaction begins spontaneously.

The interaction of phosphorus with iodine can lead to the formation of only phosphorus triodid due to significantly less than the remaining oxidizing halogens:

gray

Fluorine oxidizes sulfur to the highest oxidation +6, forming sulfur hexafluoride:

Chlorine and bromine react with gray, forming compounds containing sulfur in extremely not characteristic of the oxidation degrees +1 and +2. These interactions are very specific, and for the examination of the chemistry, the ability to record equations of these interactions is not necessary. Therefore, the three of the following equations are given more for familiarization:

The interaction of halogens with metals

As mentioned above, Fluoro is able to react with all metals, even as low-active as platinum and gold:

The remaining halogens react with all metals besides platinum and gold:

Halogen reactions with complex substances

Reaction reactions with halogens

More active halogens, i.e. The chemical elements of which are located above in the Mendeleev table, are able to oust less active halogens from the halogen-hydrogen acids and halides of metals:

Similarly, bromine and iodine displaces sulfur from sulfide solutions and or hydrogen sulfide:

Chlorine is a stronger oxidizing agent and oxidizes hydrogen sulfide in its aqueous solution of non-sulfur, and to sulfuric acid:

The interaction of halogens with water

Water is burning in fluorine with a blue flame in accordance with the reaction equation:

Bromine and chlorine react with water differently than fluorine. If Fluoro performed as an oxidizing agent, then chlorine and bromine are disproportionated in water, forming a mixture of acids. With this reaction reversible:

The interaction of iodine with water flows into so insignificantly low that they can be neglected and assumed that the reaction does not flow at all.

The interaction of halogens with alkalis solutions

The fluorine when interacting with an aqueous alkali solution again acts as an oxidizing agent:

The ability to record this equation is not required to pass the USE. It is enough to know the fact about the possibility of such interaction and the oxidative role of fluorine in this reaction.

Unlike fluorine, the remaining halogens in alkali solutions are disproportionate, that is, simultaneously and increase their degree of oxidation. At the same time, in the case of chlorine and bromine, depending on the temperature, it is possible in two different directions. In particular, the cold of the reaction proceeds as follows:

and when heated:

Iodine reacts with alkalis exclusively according to the second option, i.e. with iodata formation, because Hydiogenic is not stable not only when heated, but also at normal temperature and even cold.

Halogens are the most reactive group of elements in the periodic system. They consist of molecules with very low bond dissociation energies (see Table 16.1), and their atoms have seven electrons in the outer shell and therefore very electronegative. Fluorine is the most electronegative and most reactive non-metallic element in the periodic system. The reactivity of halogen gradually decreases when moving to the bottom of the group. The following section will consider the ability of halogen to oxidize metals and non-metals and is shown how this ability decreases in the fluorine direction to an end.

Halogens like oxidizing agents

When the gaseous hydrogen sulfide is passed through the chlorine water, sulfur is precipitated. The reaction proceeds by equation

In this reaction, chlorine oxidizes hydrogen sulfide, he has hydrogen. Chlorine also oxidizes before, for example, if mixing chlorine with an aqueous sulfate solution is formed sulphate

The oxidative half-reaction occurring is described by the equation

As another example of the oxidative effect of chlorine, we present synthesis of sodium chloride when sodium burning in Chlorine:

Sodium oxidation occurs in this reaction, since each sodium atom loses an electron, forming sodium ion:

Chlorine joins these electrons, forming chloride ions:

Table 16.3. Standard Halogen Electrode Potentials

Table 16.4. Standard sodium halide formation enthalpia

Oxidifiers are all halogens, from them fluorine is the strongest oxidizing agent. In tab. 16.3 The standard electrode potentials of halogens are indicated. From this table, it can be seen that the oxidative capacity of halogen gradually decreases towards the lower part of the group. This pattern can be demonstrated by adding a solution of potassium bromide into a vessel with chlorine gaseous. Chlorine oxidizes bromide ions, resulting in a bromine; This leads to the appearance of coloring at the previously colorless solution:

Thus, you can make sure that chlorine is a stronger oxidizer than bromine. In the same way, if the solution of potassium iodide is mixed with bromine, black precipitate from a solid iodine is formed. This means that the bromine oxidizes iodide ions:

Both reactions described are examples of displacement reactions (substitutions). In each case, a more reactive, that is, which is a stronger oxidizing agent, halogen displaces less reactive halogen from the solution.

Oxidation of metals. Halogens are easily oxidized by metals. Fluorine easily oxidizes all metals, excluding gold and silver. We have already mentioned that Chlorine oxidizes sodium, forming sodium chloride with him. We give another example: when the flow of gaseous chlorine is passed above the surface of heated iron sawdust, a chloride is formed solid brown substance:

Even iodine is capable, although slowly, oxidizing the metals located in the electrochemical row below it. The ease of oxidation of metals by various halogens is reduced when moving to the bottom of the VII group. This can be verified by comparing the energy of the formation of halides from the source elements. In tab. 16.4 Standard sodium halide enthalenpia are indicated in the order of movement to the lower part of the group.

Oxidation of non-metals. With the exception of nitrogen and most noble gases, Fluorine oxidizes all other non-metals. Chlorine reacts with phosphorus and gray. Carbon, nitrogen and oxygen do not react directly with chlorine, bromine or iodine. The relative reactivity of halogens to nonmetallam can be judged by comparing their reactions with hydrogen (Table 16.5).

Oxidation of hydrocarbons. Under certain conditions, halogens are oxidized by hydrocarbons.

Table 16.5. Halogen reactions with hydrogen

doroda. For example, chlorine completely clears the hydrogen from the turpentine molecule:

The oxidation of acetylene can flow with an explosion:

Reactions with water and alkalis

Fluorine reacts with cold water, forming fluoride and oxygen:

Chlorine slowly dissolves in water, forming chlorine water. Chlorine water has a small acidity due to the fact that it takes disproportionately (see section 10.2) chlorine to form hydrochloric acid and chlorothic acid:

Bromine and iodine disproportionate in water in a similar way, but the degree of disproportionation in water decreases from chlorine to anode.

Chlorine, bromine and iodine disproportionate also in alkalis. For example, in a cold dilute alkali, bromine is disproportifected to bromide ions and hypobromite-ioi (bromate -yons):

In the interaction of bromine with hot concentrated alkalis, the disharinary parting flows further:

Iodat (I), or hypoid-ion, unstable even in cold diluted alkalis. It spontaneously disproportionates with the formation of iodide ion and heodat (i) -yone.

The fluorine reaction with alkalis, as well as its reaction with water, is not similar to similar reactions of other halogen. The following reaction occurs in a cold dilute alkali:

In the hot concentrated alkali, the reaction with fluorine proceeds as follows:

Analysis on halogens and with the participation of halogen

High-quality and quantitative analysis on halogens is usually performed using a silver nitrate solution. for example

For high-quality and quantify iodine definition, a starch solution can be used. Since iodine is very little soluble in water, it is usually analyzed in the presence of potassium iodide. So come for the reason that the iodine forms a soluble triiodide ion with iodide ion

Solutions of iodides are used to analytically determine various reducing agents, for example, as well as some oxidizing agents, for example, oxidizers shift the above equilibrium to the left, releaseing iodine. Iodine is then titrated by thiosulfate (VI).

So, repeat again!

1. Atoms of all halogen have seven electrons in the outer shell.

2. To obtain halogen in laboratory conditions, the oxidation of the corresponding halogen breeding acids can be used.

3. Halogens are oxidized by metals, non-metals and hydrocarbons.

4. Halogens are disproportionated in water and alkali, forming halide ions, hypathalogenic and halogen (-yons.

5. The patterns of changing the physical and chemical properties of halogen when moving to the lower part of the group are shown in Table. 16.6.

Table 16.6. Patterns of changing the properties of halogen as the atomic number increases

6. Fluoro has abnormal properties among other halogen for the following reasons:

a) it has a low dissociation energy;

b) in fluorine connections, it exists only in one state of oxidation;

c) fluorine is the electronegative and most reactive among all non-metallic elements;

d) its reaction with water and alkalis differ from similar reactions of the remaining halogen.