§1. Chemical properties of a simple substance (st. approx. = 0).

a) Relation to oxygen.

Unlike its subgroup neighbors - silver and gold - copper reacts directly with oxygen. Copper exhibits insignificant activity towards oxygen, but in humid air it gradually oxidizes and becomes covered with a greenish film consisting of basic copper carbonates:

In dry air, oxidation occurs very slowly, and a thin layer of copper oxide forms on the surface of the copper:

Externally, copper does not change, since copper oxide (I), like copper itself, is pink. In addition, the oxide layer is so thin that it transmits light, i.e. shines through. Copper oxidizes differently when heated, for example, at 600-800 0 C. In the first seconds, oxidation proceeds to copper (I) oxide, which from the surface turns into black copper (II) oxide. A two-layer oxide coating is formed.

Q formation (Cu 2 O) = 84935 kJ.

Figure 2. Structure of the copper oxide film.

b) Interaction with water.

Metals of the copper subgroup are at the end of the electrochemical voltage series, after the hydrogen ion. Therefore, these metals cannot displace hydrogen from water. At the same time, hydrogen and other metals can displace metals of the copper subgroup from solutions of their salts, for example:

This reaction is redox, as electrons are transferred:

Molecular hydrogen displaces metals of the copper subgroup with great difficulty. This is explained by the fact that the bond between hydrogen atoms is strong and a lot of energy is spent on breaking it. The reaction occurs only with hydrogen atoms.

In the absence of oxygen, copper practically does not interact with water. In the presence of oxygen, copper slowly reacts with water and becomes covered with a green film of copper hydroxide and basic carbonate:

c) Interaction with acids.

Being in the voltage series after hydrogen, copper does not displace it from acids. Therefore, hydrochloric and dilute sulfuric acid have no effect on copper.

However, in the presence of oxygen, copper dissolves in these acids to form the corresponding salts:

The only exception is hydroiodic acid, which reacts with copper to release hydrogen and form a very stable copper (I) complex:

2 Cu + 3 HI → 2 H[ CuI 2 ] + H 2

Copper also reacts with oxidizing acids, for example, nitric acid:

Cu + 4HNO 3( conc. .) → Cu(NO 3 ) 2 +2NO 2 +2H 2 O

3Cu + 8HNO 3( diluting .) → 3Cu(NO 3 ) 2 +2NO+4H 2 O

And also with concentrated cold sulfuric acid:

Cu+H 2 SO 4(conc.) → CuO + SO 2 +H 2 O

With hot concentrated sulfuric acid :

Cu+2H 2 SO 4( conc. ., hot ) → CuSO 4 + SO 2 + 2H 2 O

With anhydrous sulfuric acid at a temperature of 200 0 C, copper (I) sulfate is formed:

2Cu + 2H 2 SO 4( anhydrous .) 200 °C → Cu 2 SO 4 ↓+SO 2 + 2H 2 O

d) Relation to halogens and some other non-metals.

Q formation (CuCl) = 134300 kJ

Q formation (CuCl 2) = 111700 kJ

Copper reacts well with halogens and produces two types of halides: CuX and CuX 2 .. When exposed to halogens at room temperature, no visible changes occur, but a layer of adsorbed molecules first forms on the surface, and then a thin layer of halides. When heated, the reaction with copper occurs very violently. We heat the copper wire or foil and lower it hot into a jar of chlorine - brown vapors will appear near the copper, consisting of copper (II) chloride CuCl 2 with an admixture of copper (I) chloride CuCl. The reaction occurs spontaneously due to the heat released. Monivalent copper halides are obtained by reacting copper metal with a solution of cuprous halide, for example:

In this case, the monochloride precipitates from solution in the form of a white precipitate on the surface of the copper.

Copper also reacts quite easily with sulfur and selenium when heated (300-400 °C):

2Cu +S→Cu 2 S

2Cu +Se→Cu 2 Se

But copper does not react with hydrogen, carbon and nitrogen even at high temperatures.

e) Interaction with non-metal oxides

When heated, copper can displace simple substances from some non-metal oxides (for example, sulfur (IV) oxide and nitrogen oxides (II, IV)), thereby forming a thermodynamically more stable copper (II) oxide:

4Cu+SO 2 600-800°C →2CuO + Cu 2 S

4Cu+2NO 2 500-600°C →4CuO + N 2

2 Cu+2 NO 500-600° C →2 CuO + N 2

§2. Chemical properties of monovalent copper (st. ok. = +1)

In aqueous solutions, the Cu + ion is very unstable and disproportionates:

Cu + ↔ Cu 0 + Cu 2+

However, copper in the (+1) oxidation state can be stabilized in compounds with very low solubility or through complexation.

a) Copper oxide (I) Cu 2 O

Amphoteric oxide. Brown-red crystalline substance. It occurs in nature as the mineral cuprite. It can be artificially obtained by heating a solution of a copper (II) salt with an alkali and some strong reducing agent, for example, formaldehyde or glucose. Copper(I) oxide does not react with water. Copper(I) oxide is transferred into solution with concentrated hydrochloric acid to form a chloride complex:

Cu 2 O+4 HCl→2 H[ CuCl2]+ H 2 O

Also soluble in a concentrated solution of ammonia and ammonium salts:

Cu 2 O+2NH 4 + →2 +

In dilute sulfuric acid it disproportionates into divalent copper and metallic copper:

Cu 2 O+H 2 SO 4(diluted) →CuSO 4 +Cu 0 ↓+H 2 O

Also, copper(I) oxide enters into the following reactions in aqueous solutions:

1. Slowly oxidized by oxygen to copper(II) hydroxide:

2 Cu 2 O+4 H 2 O+ O 2 →4 Cu(OH) 2 ↓

2. Reacts with dilute hydrohalic acids to form the corresponding copper(I) halides:

Cu 2 O+2 HГ→2CuГ↓ +H 2 O(G=Cl, Br, J)

3. Reduced to metallic copper with typical reducing agents, for example, sodium hydrosulfite in a concentrated solution:

2 Cu 2 O+2 NaSO 3 →4 Cu↓+ Na 2 SO 4 + H 2 SO 4

Copper(I) oxide is reduced to copper metal in the following reactions:

1. When heated to 1800 °C (decomposition):

2 Cu 2 O - 1800° C →2 Cu + O 2

2. When heated in a stream of hydrogen, carbon monoxide, with aluminum and other typical reducing agents:

Cu 2 O+H 2 - >250°C →2Cu +H 2 O

Cu 2 O+CO - 250-300°C →2Cu +CO 2

3 Cu 2 O + 2 Al - 1000° C →6 Cu + Al 2 O 3

Also, at high temperatures, copper(I) oxide reacts:

1. With ammonia (copper(I) nitride is formed)

3 Cu 2 O + 2 N.H. 3 - 250° C →2 Cu 3 N + 3 H 2 O

2. With alkali metal oxides:

Cu 2 O+M 2 O- 600-800°C →2 MCuO (M= Li, Na, K)

In this case, copper (I) cuprates are formed.

Copper(I) oxide reacts noticeably with alkalis:

Cu 2 O+2 NaOH (conc.) + H 2 O↔2 Na[ Cu(OH) 2 ]

b) Copper hydroxide (I) CuOH

Copper(I) hydroxide forms a yellow substance and is insoluble in water.

Easily decomposes when heated or boiled:

2 CuOH → Cu 2 O + H 2 O

c) HalidesCuF, CuWITHl, CuBrAndCuJ

All these compounds are white crystalline substances, poorly soluble in water, but highly soluble in excess NH 3, cyanide ions, thiosulfate ions and other strong complexing agents. Iodine forms only the compound Cu +1 J. In the gaseous state, cycles of the type (CuГ) 3 are formed. Reversibly soluble in the corresponding hydrohalic acids:

CuG + HG ↔H[ CuG 2 ] (Г=Cl, Br, J)

Copper(I) chloride and bromide are unstable in moist air and gradually transform into basic copper(II) salts:

4 CuG +2H 2 O + O 2 →4 Cu(OH)G (G=Cl, Br)

d) Other copper compounds (I)

1. Copper (I) acetate (CH 3 COOCu) is a copper compound that appears as colorless crystals. In water it slowly hydrolyzes to Cu 2 O, in air it is oxidized to cupric acetate; CH 3 COOCu is obtained by reduction of (CH 3 COO) 2 Cu with hydrogen or copper, sublimation of (CH 3 COO) 2 Cu in vacuum or interaction of (NH 3 OH)SO 4 with (CH 3 COO) 2 Cu in solution in the presence of H 3 COONH 3 . The substance is toxic.

2. Copper(I) acetylide - red-brown, sometimes black crystals. When dry, the crystals detonate when struck or heated. Stable when wet. When detonation occurs in the absence of oxygen, no gaseous substances are formed. Decomposes under the influence of acids. Formed as a precipitate when passing acetylene into ammonia solutions of copper(I) salts:

WITH 2 H 2 +2[ Cu(N.H. 3 ) 2 ](OH) → Cu 2 C 2 ↓ +2 H 2 O+2 N.H. 3

This reaction is used for the qualitative detection of acetylene.

3. Copper nitride - an inorganic compound with the formula Cu 3 N, dark green crystals.

Decomposes when heated:

2 Cu 3 N - 300° C →6 Cu + N 2

Reacts violently with acids:

2 Cu 3 N +6 HCl - 300° C →3 Cu↓ +3 CuCl 2 +2 N.H. 3

§3. Chemical properties of divalent copper (st. ok. = +2)

Copper has the most stable oxidation state and is the most characteristic of it.

a) Copper oxide (II) CuO

CuO is the main oxide of divalent copper. The crystals are black in color, quite stable under normal conditions, and practically insoluble in water. It occurs in nature in the form of the black mineral tenorite (melaconite). Copper(II) oxide reacts with acids to form the corresponding copper(II) salts and water:

CuO + 2 HNO 3 → Cu(NO 3 ) 2 + H 2 O

When CuO is fused with alkalis, copper(II) cuprates are formed:

CuO+2 KOH- t ° → K 2 CuO 2 + H 2 O

When heated to 1100 °C, it decomposes:

4CuO- t ° →2 Cu 2 O + O 2

b) Copper (II) hydroxideCu(OH) 2

Copper(II) hydroxide is a blue amorphous or crystalline substance, practically insoluble in water. When heated to 70-90 °C, Cu(OH)2 powder or its aqueous suspensions decomposes to CuO and H2O:

Cu(OH) 2 → CuO + H 2 O

It is an amphoteric hydroxide. Reacts with acids to form water and the corresponding copper salt:

It does not react with dilute solutions of alkalis, but dissolves in concentrated solutions, forming bright blue tetrahydroxycuprates (II):

Copper(II) hydroxide forms basic salts with weak acids. Dissolves very easily in excess ammonia to form copper ammonia:

Cu(OH) 2 +4NH 4 OH→(OH) 2 +4H 2 O

Copper ammonia has an intense blue-violet color, so it is used in analytical chemistry to determine small amounts of Cu 2+ ions in solution.

c) Copper salts (II)

Simple salts of copper (II) are known for most anions, except cyanide and iodide, which, when interacting with the Cu 2+ cation, form covalent copper (I) compounds that are insoluble in water.

Copper (+2) salts are mainly soluble in water. The blue color of their solutions is associated with the formation of the 2+ ion. They often crystallize as hydrates. Thus, from an aqueous solution of copper (II) chloride below 15 0 C, tetrahydrate crystallizes, at 15-26 0 C - trihydrate, above 26 0 C - dihydrate. In aqueous solutions, copper(II) salts are slightly hydrolyzed, and basic salts often precipitate from them.

1. Copper (II) sulfate pentahydrate (copper sulfate)

Of greatest practical importance is CuSO 4 * 5H 2 O, called copper sulfate. Dry salt has a blue color, but when slightly heated (200 0 C), it loses water of crystallization. Anhydrous salt is white. With further heating to 700 0 C, it turns into copper oxide, losing sulfur trioxide:

CuSO 4 ­-- t ° → CuO+ SO 3

Copper sulfate is prepared by dissolving copper in concentrated sulfuric acid. This reaction is described in the section "Chemical properties of a simple substance." Copper sulfate is used in the electrolytic production of copper, in agriculture to control pests and plant diseases, and for the production of other copper compounds.

2. Copper (II) chloride dihydrate.

These are dark green crystals, easily soluble in water. Concentrated solutions of copper chloride are green, and diluted solutions are blue. This is explained by the formation of a green chloride complex:

Cu 2+ +4 Cl - →[ CuCl 4 ] 2-

And its further destruction and the formation of a blue aqua complex.

3. Copper(II) nitrate trihydrate.

Blue crystalline substance. It is obtained by dissolving copper in nitric acid. When heated, the crystals first lose water, then decompose with the release of oxygen and nitrogen dioxide, turning into copper (II) oxide:

2Cu(NO 3 ) 2 -- t° →2CuO+4NO 2 +O 2

4. Hydroxocopper (II) carbonate.

Copper carbonates are unstable and are almost never used in practice. Only the basic copper carbonate Cu 2 (OH) 2 CO 3, which occurs in nature in the form of the mineral malachite, is of some importance for the production of copper. When heated, it easily decomposes, releasing water, carbon monoxide (IV) and copper oxide (II):

Cu 2 (OH) 2 CO 3 -- t° →2CuO+H 2 O+CO 2

§4. Chemical properties of trivalent copper (st. ok. = +3)

This oxidation state is the least stable for copper, and copper(III) compounds are therefore the exception rather than the "rule". However, some trivalent copper compounds do exist.

a) Copper (III) oxide Cu 2 O 3

This is a crystalline substance, dark garnet in color. Does not dissolve in water.

It is obtained by oxidation of copper(II) hydroxide with potassium peroxodisulfate in an alkaline medium at negative temperatures:

2Cu(OH) 2 +K 2 S 2 O 8 +2KOH -- -20°C →Cu 2 O 3 ↓+2K 2 SO 4 +3H 2 O

This substance decomposes at a temperature of 400 0 C:

Cu 2 O 3 -- t ° →2 CuO+ O 2

Copper(III) oxide is a strong oxidizing agent. When reacting with hydrogen chloride, chlorine is reduced to free chlorine:

Cu 2 O 3 +6 HCl-- t ° →2 CuCl 2 + Cl 2 +3 H 2 O

b) Copper cuprates (C)

These are black or blue substances, unstable in water, diamagnetic, the anion is a ribbon of squares (dsp 2). Formed by the interaction of copper(II) hydroxide and alkali metal hypochlorite in an alkaline environment:

2 Cu(OH) 2 + MClO + 2 NaOH→2MCuO 3 + NaCl +3 H 2 O (M= Na- Cs)

c) Potassium hexafluorocuprate(III)

Green substance, paramagnetic. Octahedral structure sp 3 d 2. Copper fluoride complex CuF 3, which in a free state decomposes at -60 0 C. It is formed by heating a mixture of potassium and copper chlorides in a fluorine atmosphere:

3KCl + CuCl + 3F 2 → K 3 + 2Cl 2

Decomposes water to form free fluorine.

§5. Copper compounds in oxidation state (+4)

So far, science knows only one substance where copper is in the oxidation state +4, this is cesium hexafluorocuprate(IV) - Cs 2 Cu +4 F 6 - an orange crystalline substance, stable in glass ampoules at 0 0 C. It reacts violently with water. It is obtained by fluoridation at high pressure and temperature of a mixture of cesium and copper chlorides:

CuCl 2 +2CsCl +3F 2 -- t ° r → Cs 2 CuF 6 +2Cl 2

COPPER AND ITS COMPOUNDS

LESSON IN 11TH NATURAL SCIENCE CLASS

To increase the cognitive activity and independence of students, we use lessons for collective study of material. In such lessons, each student (or pair of students) receives a task, the completion of which he must report on in the same lesson, and his report is recorded by the rest of the class students in notebooks and is an element of the content of the lesson’s educational material. Each student contributes to the class's learning about the topic.
During the lesson, the students’ work mode changes from intraactive (a mode in which information flows are closed within the students, typical for independent work) to interactive (a mode in which information flows are two-way, i.e. information goes both from the student and to the student, information is exchanged). In this case, the teacher acts as the organizer of the process, corrects and supplements the information provided by the students.
Lessons for collective study of material consist of the following stages:
1st stage - installation, in which the teacher explains the goals and program of work for the lesson (up to 7 minutes);
Stage 2 – independent work of students according to instructions (up to 15 minutes);
Stage 3 – exchange of information and summing up the lesson (takes up all the remaining time).
The lesson “Copper and its compounds” is designed for classes with in-depth study of chemistry (4 hours of chemistry per week), is conducted over two academic hours, the lesson updates students’ knowledge on the following topics: “General properties of metals”, “Attitude towards metals with concentrated sulfuric acid” acid, nitric acid”, “Qualitative reactions to aldehydes and polyhydric alcohols”, “Oxidation of saturated monohydric alcohols with copper(II) oxide”, “Complex compounds”.
Before the lesson, students receive homework: repeat the listed topics. The teacher's preliminary preparation for the lesson consists of drawing up instruction cards for students and preparing sets for laboratory experiments.

DURING THE CLASSES

Installation stage

The teacher poses to the students the purpose of the lesson: based on existing knowledge about the properties of substances, predict, practically confirm, summarize information about copper and its compounds.
Students compose the electronic formula of the copper atom, find out what oxidation states copper can exhibit in compounds, what properties (redox, acid-base) copper compounds will have.
A table appears in the students' notebooks.

Properties of copper and its compounds

Metal	Cu 2 O – basic oxide	CuO – basic oxide
Reducing agent	CuOH is an unstable base	Cu(OH) 2 – insoluble base
	CuCl – insoluble salt	CuSO 4 – soluble salt
	Possess redox duality	Oxidizing agents

Independent work stage

To confirm and supplement assumptions, students perform laboratory experiments according to the instructions and write down the equations of the reactions performed.

Instructions for independent work in pairs

1. Heat the copper wire in a flame. Notice how its color has changed. Place hot calcined copper wire in ethyl alcohol. Notice the change in its color. Repeat these manipulations 2-3 times.
Check to see if the ethanol smell has changed.

2. Write down two reaction equations corresponding to the transformations carried out. What properties of copper and its oxide are confirmed by these reactions?
Add hydrochloric acid to copper(I) oxide.

3. a) Place a zinc granule into a solution of copper(II) sulfate. If the reaction does not proceed, heat the solution. b) Add 1 ml of sulfuric acid to copper(II) oxide and heat.
What are you observing? Write down the reaction equations.

4. What properties of copper compounds are confirmed by these reactions?
Place a strip of universal indicator into the copper(II) sulfate solution.
Explain the result. Write down the ionic equation for hydrolysis in step I.
Add a solution of honey(II) sulfate to the sodium carbonate solution.

5.
What are you observing? Write down the equation for the joint hydrolysis reaction in molecular and ionic forms.
What are you observing?
Add ammonia solution to the resulting precipitate.

6. What changes have occurred? Write down the reaction equations. What properties of copper compounds do these reactions prove?
Add a solution of potassium iodide to copper(II) sulfate.

7. What are you observing? Write an equation for the reaction.
What property of copper(II) does this reaction prove?
Place a small piece of copper wire in a test tube with 1 ml of concentrated nitric acid. Close the test tube with a stopper.
What are you observing? (Take the test tube under the traction.) Write down the reaction equation.

8. Pour hydrochloric acid into another test tube and place a small piece of copper wire in it.
What are you observing? Explain your observations. What properties of copper are confirmed by these reactions?

9. Pour hydrochloric acid into another test tube and place a small piece of copper wire in it.
What are you observing? Write down the equation for the joint hydrolysis reaction in molecular and ionic forms.
Add excess sodium hydroxide to copper(II) sulfate.
What are you observing? Heat the resulting precipitate. What happened? Write down the reaction equations. What properties of copper compounds are confirmed by these reactions?

10. Pour hydrochloric acid into another test tube and place a small piece of copper wire in it.
What are you observing? Write down the equation for the joint hydrolysis reaction in molecular and ionic forms.
Add glycerin solution to the resulting precipitate.
What changes have occurred? Write down the reaction equations. What properties of copper compounds do these reactions prove?

Add glucose solution to the resulting precipitate and heat.

11. What happened? Write down the reaction equation using the general formula of aldehydes to denote glucose
What property of the copper compound does this reaction prove?

Add to copper(II) sulfate: a) ammonia solution; b) sodium phosphate solution.

What are you observing? Write down the reaction equations.

Procedure for discussing the chemical properties of copper compounds

1. How does copper react with acids, what other substances can copper react with?

The reaction equations for copper are written with:

Concentrated and diluted nitric acid:

Cu + 4HNO 3 (conc.) = Cu(NO 3) 2 + 2NO 2 + 2H 2 O,
3Cu + 8HNO 3 (diluted) = 3Cu(NO 3) 2 + 2NO + 4H 2 O;

Concentrated sulfuric acid:

Cu + 2H 2 SO 4 (conc.) = CuSO 4 + SO 2 + 2H 2 O;

Oxygen:

2Cu + O 2 = 2CuO;

Cu + Cl 2 = CuCl 2;

Hydrochloric acid in the presence of oxygen:

2Cu + 4HCl + O 2 = 2CuCl 2 + 2H 2 O;

Iron(III) chloride:

2FeCl 3 + Cu = CuCl 2 + 2FeCl 2.

2. What properties do copper(I) oxide and chloride exhibit?

Attention is drawn to the basic properties, the ability to form complexes, and redox duality. The equations for the reactions of copper(I) oxide with are written:

Hydrochloric acid until CuCl is formed:

Cu 2 O + 2HCl = 2CuCl + H 2 O;

Excess HCl:

CuCl + HCl = H;

Reduction and oxidation reactions of Cu 2 O:

Cu 2 O + H 2 = 2Cu + H 2 O,

2Cu2O + O2 = 4CuO;

Disproportionation when heated:

Cu 2 O = Cu + CuO,
2CuCl = Cu + CuCl 2 .

3. What properties does copper(II) oxide exhibit?

Attention is drawn to the basic and oxidative properties. The equations for the reactions of copper(II) oxide with are written:

Acid:

CuO + 2H + = Cu 2+ + H 2 O;

Ethanol:

C 2 H 5 OH + CuO = CH 3 CHO + Cu + H 2 O;

Hydrogen:

CuO + H 2 = Cu + H 2 O;

Aluminum:

3CuO + 2Al = 3Cu + Al 2 O 3.

4. What properties does copper(II) hydroxide exhibit?

Attention is drawn to oxidative, basic properties, the ability to form complexes with organic and inorganic compounds. Reaction equations are written with:

Aldehyde:

RCHO + 2Cu(OH) 2 = RCOOH + Cu 2 O + 2H 2 O;

Acid:

Cu(OH) 2 + 2H + = Cu 2+ + 2H 2 O;

Ammonia:

Cu(OH) 2 + 4NH 3 = (OH) 2;

Glycerin:

Decomposition reaction equation:

Cu(OH) 2 = CuO + H 2 O.

5. What properties do copper(II) salts exhibit?

Attention is drawn to the reactions of ion exchange, hydrolysis, oxidative properties, and complexation. The equations for the reactions of copper sulfate with:

Sodium hydroxide:

Cu 2+ + 2OH – = Cu(OH) 2 ;

Sodium phosphate:

3Cu 2+ + 2= Cu 3 (PO 4) 2;

Cu 2+ + Zn = Cu + Zn 2+ ;

Potassium iodide:

2CuSO 4 + 4KI = 2CuI + I 2 + 2K 2 SO 4;

Ammonia:

Cu 2+ + 4NH 3 = 2+ ;

and reaction equations:

Hydrolysis:

Cu 2+ + HOH = CuOH + + H + ;

Co-hydrolysis with sodium carbonate to form malachite:

2Cu 2+ + 2 + H 2 O = (CuOH) 2 CO 3 + CO 2.

In addition, you can tell students about the interaction of copper(II) oxide and hydroxide with alkalis, which proves their amphoteric nature:

Cu(OH) 2 + 2NaOH (conc.) = Na 2,

Cu + Cl 2 = CuCl 2,

Cu + HgCl 2 = CuCl 2 + Hg,

2Cu + 4HCl + O 2 = 2CuCl 2 + 2H 2 O,

CuO + 2HCl = CuCl 2 + H 2 O,

Cu(OH) 2 + 2HCl = CuCl 2 + 2H 2 O,

CuBr 2 + Cl 2 = CuCl 2 + Br 2,

(CuOH) 2 CO 3 + 4HCl = 2CuCl 2 + 3H 2 O + CO 2,

2CuCl + Cl 2 = 2CuCl 2,

2CuCl = CuCl 2 + Cu,

CuSO 4 + BaCl 2 = CuCl 2 + BaSO 4.)

Exercise 3. Make chains of transformations corresponding to the following schemes and carry them out:

Task 1. The copper-aluminum alloy was treated first with an excess of alkali and then with an excess of dilute nitric acid.
.

(Calculate the mass fractions of metals in the alloy if it is known that the volumes of gases released in both reactions (under the same conditions) are equal Answer

. Mass fraction of copper – 84%.) Task 2.

(When 6.05 g of copper(II) nitrate crystalline hydrate was calcined, 2 g of a residue was obtained. Determine the formula of the original salt. Answer.

Cu(NO 3) 2 3H 2 O.) Task 3.

(When 6.05 g of copper(II) nitrate crystalline hydrate was calcined, 2 g of a residue was obtained. Determine the formula of the original salt. A copper plate weighing 13.2 g was dipped into 300 g of iron(III) nitrate solution with a salt mass fraction of 0.112. When it was taken out, it turned out that the mass fraction of iron(III) nitrate became equal to the mass fraction of the formed copper(II) salt. Determine the mass of the plate after it was removed from the solution.

10 years) Homework.

Learn the material written in the notebook. Make a chain of transformations for copper compounds, containing at least ten reactions, and carry it out.

1. LITERATURE Puzakov S.A., Popkov V.A.
2. A manual on chemistry for applicants to universities. Programs. Questions, exercises, tasks. Sample exam papers. M.: Higher School, 1999, 575 p. Kuzmenko N.E., Eremin V.V.

2000 problems and exercises in chemistry. For schoolchildren and applicants. M.: 1st Federative Book Trading Company, 1998, 512 p.

General information about the hydrolysis of copper (II) chloride

DEFINITION Copper(II) chloride

– a medium salt formed by a weak base – copper (II) hydroxide (Cu(OH) 2) and a strong acid – hydrochloric (hydrochloric) (HCl). Formula - CuCl 2.

Represents crystals of yellow-brown (dark brown) color; in the form of crystalline hydrates - green. Molar mass – 134 g/mol.

Rice. 1. Copper(II) chloride. Appearance.

Hydrolysis of copper(II) chloride

Hydrolyzes at the cation. The nature of the environment is acidic. Theoretically, a second stage is possible. The hydrolysis equation is as follows:

First stage:

Cu 2+ + HOH ↔ CuOH + + H + (hydrolysis by cation);

Cu 2+ + 2Cl - + HOH ↔ CuOH + + 2Cl - + H + (ionic equation);

CuCl 2 + H 2 O ↔ Cu(OH)Cl +HCl (molecular equation).

Second stage:

Cu(OH)Cl ↔ CuOH + + Cl - (salt dissociation);

CuOH + + HOH ↔ Cu(OH) 2 ↓ + H + (hydrolysis by cation);

CuOH + + Cl - + HOH ↔ Cu(OH) 2 ↓ + Cl - + H + (ionic equation);

Cu(OH)Cl + H 2 O ↔ Cu(OH) 2 ↓ + HCl (molecular equation).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	Write down the equation for the electrolysis of a solution of copper (II) chloride. What mass of substance will be released at the cathode if 5 g of copper (II) chloride is subjected to electrolysis?
Solution	Let us write the dissociation equation for copper (II) chloride in an aqueous solution: CuCl 2 ↔ Cu 2+ +2Cl - . Let us conventionally write down the electrolysis scheme: (-) Cathode: Cu 2+, H 2 O. (+) Anode: Cl - , H 2 O. Cu 2+ +2e → Cu o ; 2Cl - -2e → Cl 2. Then, the electrolysis equation for an aqueous solution of copper (II) chloride will look like this: CuCl 2 = Cu + Cl 2. Let's calculate the amount of copper (II) chloride using the data specified in the problem statement (molar mass - 134 g/mol): υ(CuCl 2) = m(CuCl 2)/M(CuCl 2) = 5/134 = 0.04 mol. According to the reaction equation υ(CuCl 2) = υ(Cu) =0.04 mol. Then we calculate the mass of copper released at the cathode (molar mass – 64 g/mol): m(Cu)= υ(Cu)×M(Cu)= 0.04 ×64 = 2.56 g.
Calculate the mass fractions of metals in the alloy if it is known that the volumes of gases released in both reactions (under the same conditions) are equal	The mass of copper released at the cathode is 2.56 g.