Potassium can be obtained by electrolysis on coal electrodes. Potassium properties and its interaction with water. Potassium interaction with complex substances

Potassium is a nineteenth element of the periodic table of Mendeleev, refers to alkaline metals. This is a simple substance that under normal conditions is in solid aggregate state. Potassium boils at 761 ° C. The melting point of the element is 63 ° C. Potassium has a silver and white painting with a metal glitter.

Chemical properties of potassium

Potassium - with high chemical activity, so it can not be stored outdoors: alkaline metal Instantly enters the reaction with the surrounding substances. This chemical element refers to the I group and IV period of the Mendeleev table. Potassium has all the properties characteristic of metals.

It interacts S. simple substanceswhich includes halogens (bromine, chlorine, fluorine, iodine) and phosphorus, nitrogen and oxygen. Potassium interaction with oxygen is called oxidation. During this chemical reaction, oxygen and potassium are consumed in a molar ratio of 4: 1, as a result of which potassium oxide is formed in the amount of two parts. Such interaction can be expressed by the reaction equation:

4K + O₂ \u003d 2k₂o

During the burning of potassium, a flame of bright purple color is observed.

Such interaction is considered a qualitative response to potassium definition. Potassium reactions with halogens are called in accordance with the names of the chemical elements: it is fluoridation, ionizing, bromination, chlorination. Such interactions are attachment reactions. An example is a reaction between potassium and chlorine, as a result of which potassium chloride is formed. To carry out such interaction take two pile of potassium and one mol. As a result, two pyllation potassium is formed:

2k + s_ \u003d 2x_

Molecular structure of potassium chloride

When burning outdoors, potassium and nitrogen are spent in a molar ratio of 6: 1. As a result of this interaction, potassium nitride is formed in the number of two parts:

6k + n₂ \u003d 2k₃n

The compound is crystals of green-black. With Phosphorus Potassies responds to the same principle. If you take 3 Potassium Potassium and 1 mol of phosphorus, it will turn out 1 mole of phosphide:

3k + p \u003d K₃r

Potassium reacts with hydrogen, forming hydride:

2k + H₂ \u003d 2kn

All reactions of attachment occur at high temperatures.

Potassium interaction with complex substances

Potassium reactions include water, salts, acids and oxides with complex substances. Since potassium is an active metal, it displaces hydrogen atoms from their compounds. An example is a reaction occurring between potassium and hydrochloric acid. It takes 2 pile of potassium and acid. As a result of the reaction, 2 pylons of potassium chloride and 1 mol of hydrogen are formed:

2k + 2nsі \u003d 2x_ + n₂

It is worth considering the process of interaction of potassium with water. Potassium strictly interacts with water. It moves along the surface of the water, it pushes the released hydrogen:

2K + 2H₂O \u003d 2KOH + H₂

During the reaction, a unit of time is distinguished by a lot of heat, which leads to the ignition of potassium and the highlighted hydrogen. This is a very interesting process: when potassium contacts, the purple flame cracks and quickly moves along the surface of the water. At the end of the reaction there is a flash with spraying of droplets of burning potassium and reaction products.

Potassium reaction with water

The main final product of potassium reaction with water is potassium hydroxide (alkali). Potassium reaction equation with water:

4K + 2H₂o + O₂ \u003d 4KOH

Attention! Do not try to repeat this experience yourself!

With incorrect experiment, you can get a burn alkali. For the reaction, a crystallizer with water is usually used, which is placed a piece of potassium. As soon as hydrogen ceases burning, many want to look into the crystallizer. At this point, the final stage of the potassium reaction with water is occurring, accompanied by a weak explosion and splashing the resulting hot alkali. Therefore, for safety reasons, it is worth staying at some distance from the laboratory table until the reaction is completely complete. You will find the most spectacular experiences that can be done with children at home.

Potassium structure

Potassium atom consists of a kernel, which contains protons and neutrons, and electrons rotating around it. The number of electrons is always equal to the number of protons located inside the kernel. When disconnecting the electron or when it is connected to the atm, it ceases to be neutral and turns into an ion. Ions are divided into cations and anions. Cations possess a positive charge, anions are negative. When connected to an electron atom, it turns into an anion; If one electron leaves its orbit, the neutral atom turns into the cation.

The serial number of potassium in periodic table Mendeleev - 19. So, protons in the core chemical element It is also 19. Conclusion: electrons around the kernel is located 19. The number of protons in the structure is determined as follows: from the atomic mass to take away the sequence number of the chemical element. Conclusion: 20 protons are in potassium kernel. Potassium belongs to the IV period, has 4 "orbits", on which electrons staying in constant motion are evenly disposed. On the first "orbit" there are 2 electrons, on the second - 8; On the third and on the last, fourth "orbit", 1 electron rotates. This explains the high level of potassium chemical activity: its last "orbit" is not fully filled, therefore the element tends to connect with other atoms. As a result, the electrons of the last orbits of the two elements will become common.

Using a funnel and a glass sticks, pour inside the sprawl-reactor sprinkler, then alkali, close the hole with a piece of scotch and shake the content. Next, attach the receiver. Its bottom hole (for hydrogen exit) should be closed with a nail. Gently sweep the joint of the reactor and the receiver of Alabasra Cashier (take it quite a little bit). Waving 5 minutes, having a hairdryer with a hairdryer about 4-5 minutes.

Now carefully screw the wet wool on the tice of the receiver, retreating from the edges of 5-8 mm, and fix it with a thin wire.

Initially, we remove the nail-pinch. Then gradually warm the balloon with the reaction mixture of the burner (you can use a soldering lamp to save).

For heating, I used a butanium canister and a large burner-nozzle mentioned above. The combustible gas inside the canopy is cooled, and with time the flame decreases a bit, so I had to warm the butan can be warm.

Watch that half the "retort" was heated to orange casting, the receiver's throat must be heated before the start of red cagine. Warm about 13-14 minutes. The reaction is first accompanied by the appearance of a purple flame emerging from the receiver, then it gradually decreases and disappears, then you can reduce the hole, inserting a nail (loosely and gap). In the course of the reaction, we gradually wipe the cotton pipette, not allowing water to the joints.

Staying heating, insert tightly tight. Give the device to cool to room temperature! I just took it on the frost. Then remove the wool, and we ereate the tracks of water.

Prepare a place in advance where you will scratch potassium from the receiver. Remember about the danger of fire! You must have gasoline, tweezers, homemade spatula scraper, potassium storage capacity with inert liquid, like kerosene or oil. It is desirable that the fluid is dried. Let's scrape the plaster and disperse the receiver. Immediately on the throat of the receiver we put on a piece of polyethylene and add it to the plasticine (or make a cork in advance). Overlook the half of the receiver, the main part of potassium was condensed in the left side (which was attached to the reactor to the reactor), only potassium traces were inside the right side (the receiver structure is shown in the photo). Pour gasoline to the left side (I used hexane). This is done to protect the metal from oxidation (gasoline is good because it will evaporate without a trace, and it will be possible to use the refrigerator again without disturbing the gypsum smear). The operation is carried out in protective glasses!

The spatula square the metal from the walls, then put it with a tweezers in the storage tank. Remember, the small chips of potassium are oxidized in the air so fast that they can ignite. It is easy to see, if you thoroughly flatten a knife snapped slice of potassium on a piece of paper (better filter or toilet) - Potassium is usually flammable. Part of the metal will be in the form of small chips and grains. They can be collected flushing with gasoline into storage tank or dry cup. They will be useful for reaction with water: even small grains are burning with beautiful purple lights.

I managed to collect about 1.1 g of potassium to bures (0.7-0.8 g in the form of a compact mass). A total formed somewhere 1.3 g of metal. Part of potassium in the form of residues I did not collect, lasted the paper from hexane and tweezers moved to water (it is convenient to just shake the grains from paper). After the reaction, it is necessary to remove the traces of the metal from the receiver, the right half ("bottom") simply throw into the water on the elongated hand and immediately go away. Left half let him lie in the air, while traces of potassium partially oxidize, then remove them with wet wool on the wire (without damaging the gypsum smelting). Then rinse the receiver with a pipette and dry it with a napkin (carefully, do not direct the hole on yourself).

Topic 1.6. Redox reactions.

Questions on the previously studied topic:

1. In which cases of electrolysis of aqueous solutions of salts:

a) hydrogen is distinguished on the cathode;

b) oxygen is released on the anode;

c) Passes simultaneous recovery of metal cations and water hydrogen cations?

1. What processes occurring on electrodes are combined with the common name "" Electrolysis ""?
2. What is the difference between the electrolysis of the melt of the caustic natra from the electrolysis of its solution?
3. With which pole battery is a positive or negative, a metal part should be connected when it is chromed.
4. Reveal the value of electrolysis; The concept is electrolysis.
5. What chemical processes occur at the cathode and anode with the electrolysis of the solution of potassium iodide? Melt iodide potassium?
6. Make electrolysis schemes using coal electrodes of melts and solutions of the following salts: KSL.
7. In which sequence, cations will be restored during the electrolysis of their salts of the same concentration (insoluble anode) of the following composition: Al, SN, AG, MN?
8. Explain why metal potassium cannot be obtained at electrolysis coal electrodes aquatic solution Potassium chloride, but can be obtained by the electrolysis of the melt of this salt?
9. With the electrolysis of the aqueous solution of silver nitrate on the cathode, it is formed:

a) Ag b) NO 2 C) NO D) H 2?

knowthe main concepts and essence of oxidative recovery reactions, the rules for the preparation of redox reactions by the method of electronic balance;

be able toclassify reactions from the point of view of oxidation; Define and apply concepts: "Degree of oxidation", "Oxidifiers and reducing agents", "Oxidation and recovery processes"; make an electronic balance for oxidative and restoration reactions and apply it to arrange coefficients in the molecular equation.

Changing the properties of elements depending on the structure of their atoms

Having studied earlier types chemical reactions, the structure of molecules, the relationship of the main classes chemical compounds, It can be said that most reactions - addition, decomposition and substitution, proceed with a change in the degree of oxidation of atoms of reactants, and only in the exchange reactions this does not occur.

Reactions, resulting in which the degree of oxidation of the elements is changed, are called redox.

There are several ways to compile equations of oxidial-restorative reactions. Let us dwell on the electronic balance based on the definition of the total number of moving electrons. For example:

Mno 2 + kslo 3 + kon \u003d k 2 mno 4 + ksl + n 2 o

We define the atoms of which elements changed the degree of oxidation:

Mn → Mn Sl → SL

Determine the number of lost (-) and obtained (+) electrons:

Mn - 2. e. → Mn SL + 6 e. → СL.

The number of lost and obtained electrons should be the same. Both semed processing processes are as follows:

restorator Mn - 2 e.ˉ → Mn 3 3mn - 6 e.ˉ → 3mn oxidation

oxidizer Sl + 6 e.ˉ → SL 1 Sl + 6 e.ˉ → SL Restoration

The main coefficients during the oxidizing agent and the reducing agent are transferred to the reaction equation

3mno 2 + KSLO 3 + 6Cone \u003d 3K 2 mno 4 + ksl + 3n 2 o

The process of turning the manganese +4 in the manganese +6 there is a provision of returns (loss) of electrons, i.e. oxidation; The process of turning Cl (+5) in Cl (-1) is the process of obtaining electrons, i.e. Recovery process. The MNO 2 substance is a reducing agent, and KSLO 3 is an oxidizing agent.

Sometimes one of the substances involved in the reaction performs two functions at once: oxidizing agent (or reducing agent) and saline. Consider as an example reaction

Zn + NNO 3 \u003d Zn (NO 3) 2 + NN 4 NO 3 + H 2 O

We will make a half-formation for the oxidizing agent and reducing agent. Zinc loses two electrons, and nitrogen N (+5) acquires eight electrons:

Zn - 2. e.ˉ → Zn 8 4

N + 8. e.ˉ → N 2 1

Thus, the oxidation of the four zinc atoms requires eight HNO 3 molecules and two HNO 3 molecules to salt formation.

4ZN + 2NNO 3 + 8NNO 3 \u003d 4ZN (NO 3) 2 + NN 4 NO 3 + 3N 2

4ZN + 10NNO 3 \u003d 4ZN (NO 3) 2 + NN 4 NO 3 + 3N 2 O

Types of equations of redox reactions.

OXICE Oxidizers and reducing agents.

Redox reactions are separated into three groups: intermolecular, intramolecular and disproportionation reactions.

Reactions in which one substance serves as an oxidizing agent, and the other is a reducing agent, called intermolecular reactions, eg:

2kmno 4 + 16nsl \u003d 2MNSL 2 + 5СL 2 + 2xl + 8n 2 o

Intermolecular reactions also include reactions between substances in which the interacting atoms of the same element have a different degree of oxidation:

2H 2 S + SO 2 \u003d 3S + 2H 2 O

Reactions that proceed with a change in the degree of oxidation of atoms in the same molecule called intramolecular reactions, eg:

2KCLO 3 \u003d 2KCL + 3O 2

Intramolecular can be attributed to reactions in which the atoms of the same element have different degrees Oxidations:

NH 4 NO 3 \u003d N 2 O + H 2 O

Reactions in which oxidative and reduction functions perform atoms of one element in the same degree of oxidation, called disproportionation reactions, eg:

2Na 2 O 2 + 2 o 2 \u003d 2NAO 3 + O 2

Oxidifiers

The oxidative ability of an atom or ion, as already mentioned, is an electron affinity, i.e. The ability to take electrons.

Oxidifiers are:

1. All non-metal atoms. The strongest oxidants are halogen atoms, as they are capable of accepting only one, electron. With a decrease in the number of the group, the oxidative abilities of atoms of non-metals located in them are falling. Therefore, non-metallulov atoms of the IV group are the weakest oxidizers. In groups from top to bottom, the oxidative properties of non-metal atoms are also reduced due to an increase in atomic radii.

2. Positively charged metal ions in a state of high oxidation, for example:

KMNO 4, K 2, 4, V 2 O 5, MNO 2, etc.

In addition, oxidizing agents are metal ions with a low degree of oxidation, for example:

AG, NG, FE, CU, etc.

3. Concentrated NNO 3 and H 2 SO 4 acids.

Restores

Restorers can be:

1. Atoms of all elements, except, NE, Ar, F. The most easily lose electrons of the atoms of those elements that have one, two, three electrons on the latter layer.

2. Positively charged metal ions that are low oxidation, for example:

FE, SG, MN, SN, CU.

3. Negatively charged ions, for example: SLˉ, VGˉ, Iˉ, S 2 ˉ.

4. Weak acids and their salts, for example: H 2 SO 3 and K 2 SO 3; NNO 2 and KNO 2.

Questions on the topic studied:

1. What reactions are called redox? What is the difference between redox reactions from other chemical reactions?

1. Why metals in compounds show only positive degrees of oxidation, and non-metals - as positive and negative?
2. What substances are called oxidizing agents and what reducing agents?
3. How can one judge the nature of the connection between atoms in the molecule in relative electronegativity?
4. What is the connection between the energy of the affinity of the electron and the oxidative ability of the chemical element?
5. For whatever complex substances, only oxidizing properties are characteristic? In what cases complex substances can act as oxidizing agents and reducing agents?
6. In the following reaction equations, determine the oxidizing agent and reducing agent, their degree of oxidation, spread the coefficients:

a) ngs + nno 3 + nsl → ngsl 2 + s + no + n 2 o

b) SNCL 2 + K 2 CR 2 O 7 + H 2 SO 4 → SN (SO 4) 2 + SNCl 4 + CR 2 (SO 4) 3 + K 2 SO 4 + H 2 O

c) ASN 3 + AGNO 3 + H 2 O → H 3 ASO 4 + AG + NNO 3

1. In the following reactions in which the oxidizing agent and the reducing agent are in the same substance (reaction of intramolecular oxidation - recovery), arrange the coefficients:

a) NN 4 NO 3 → N 2 O + H 2 O

b) KSLO 3 → KSL + O 2

c) AG 2 Oh → Ag + O 2

1. For disproportionation reactions (self-examination - self-healing), write electronic circuits and arrange the coefficients:

a) K 2 MNO 4 + H 2 O → KMNO 4 + MNO 2 + con

b) NSLO 3 → CLO 2 + NSLO 4

c) NNO 2 → NNO 3 + NO + N 2

1. Which of the reduced reactions refer to intramolecular and which - to the reactions of disproportionation:

a) Ng (NO 3) 2 → NG + NO 2 + O 2

b) Cu (NO 3) 2 → SUO + NO 2 + O 2

c) K 2 SO 3 → K 2 SO 4 + K 2 s

d) (NH 4) 2 CR 2 O 7 → N 2 + CR 2 O 3 + H 2 O

Pick the coefficients to each reaction.

Literature: 1, 2,3.