Types of reactions: All chemical reactions are divided into simple and complex. Simple chemical reactions, in turn, are usually divided into four types: compound reactions, decomposition reactions, substitution reactions and exchange reactions.
D. I. Mendeleev defined a compound as a reaction, “in which one of two substances occurs. An example compound chemical reaction heating of powders of iron and sulfur can serve, - in this case, iron sulfide is formed: Fe + S = FeS. Combination reactions include the processes of combustion of simple substances (sulfur, phosphorus, carbon, ...) in air. For example, carbon burns in air C + O 2 \u003d CO 2 (of course, this reaction proceeds gradually, carbon monoxide CO is first formed). Combustion reactions are always accompanied by the release of heat - they are exothermic.
Decomposition chemical reactions, according to Mendeleev, “cases are inverse to the connection, that is, those in which one substance gives two, or, in general, a given number of substances is a greater number of them. An example of a decomposition reaction between the two is the chemical reaction of the decomposition of chalk (or limestone under the influence of temperature): CaCO 3 → CaO + CO 2. The decomposition reaction generally requires heating. Such processes are endothermic, that is, they proceed with the absorption of heat.
In reactions of the other two types, the number of reactants is equal to the number of products. If a simple substance and a complex substance interact, then this chemical reaction is called chemical substitution reaction: For example, by dipping a steel nail into a solution of copper sulfate, we get iron sulfate (here iron displaced copper from its salt) Fe + CuSO 4 → FeSO 4 + Cu.
Reactions between two complex substances in which they exchange their parts are referred to as chemical reactions of exchange. A large number of them occur in aqueous solutions. An example of a chemical exchange reaction is the neutralization of an acid with an alkali: NaOH + HCl → NaCl + H 2 O. Here, in the reagents (substances on the left), the hydrogen ion from the HCl compound is exchanged with the sodium ion from the NaOH compound, resulting in the formation of a sodium chloride solution in water
Reaction types and their mechanisms are shown in the table:
|
compound chemical reactions Example: From several simple or complex substances, one complex substance is formed |
decomposition chemical reactions Example: From a complex substance, several simple or complex substances are formed |
chemical substitution reactions Example: An atom of a simple substance replaces one of the atoms of a complex |
ion exchange chemical reactions Example: Compounds exchange their constituents |
However, many reactions do not fit into the above simple scheme. For example, a chemical reaction between potassium permanganate (potassium permanganate) and sodium iodide cannot be attributed to any of the indicated types. Such reactions are usually called redox reactions, For example:
2KMnO 4 + 10NaI + 8H 2 SO 4 → 2MnSO 4 + K 2 SO 4 + 5Na 2 SO 4 + 5I 2 + 8H 2 O.
Signs of chemical reactions
Signs of chemical reactions. They can be used to judge whether a chemical reaction between the reagents has passed or not. These signs include the following:
Color change (for example, light iron is covered in humid air with a brown coating of iron oxide - a chemical reaction of the interaction of iron with oxygen).
- Precipitation (for example, if carbon dioxide is passed through a lime solution (calcium hydroxide solution), a white insoluble precipitate of calcium carbonate will fall out).
- Emission of gas (for example, if you drop citric acid on baking soda, carbon dioxide will be released).
- The formation of weakly dissociated substances (for example, reactions in which one of the reaction products is water).
- The glow of the solution.
An example of the glow of a solution is a reaction using a reagent such as a solution of luminol (luminol is a complex chemical that can emit light during chemical reactions).
Redox reactions
Redox reactions- constitute a special class of chemical reactions. Their characteristic feature is a change in the oxidation state of at least a pair of atoms: the oxidation of one (loss of electrons) and the reduction of the other (addition of electrons).
Compounds that lower their oxidation state - oxidizers, and increasing the degree of oxidation - reducing agents. For example:
2Na + Cl 2 → 2NaCl,
- here the oxidizing agent is chlorine (it attaches electrons to itself), and the reducing agent is sodium (it gives up electrons).
The substitution reaction NaBr -1 + Cl 2 0 → 2NaCl -1 + Br 2 0 (typical for halogens) also refers to redox reactions. Here, chlorine is an oxidizing agent (accepts 1 electron), and sodium bromide (NaBr) is a reducing agent (a bromine atom gives up an electron).
The decomposition reaction of ammonium dichromate ((NH 4) 2 Cr 2 O 7) also refers to redox reactions:
(N -3 H 4) 2 Cr 2 +6 O 7 → N 2 0 + Cr 2 +3 O 3 + 4H 2 O
Another common classification of chemical reactions is their separation according to the thermal effect. Separate endothermic reactions and exothermic reactions. Endothermic reactions - chemical reactions accompanied by the absorption of ambient heat (remember cooling mixtures). Exothermic (vice versa) - chemical reactions accompanied by the release of heat (for example, combustion).
Dangerous chemical reactions : "BOMB IN THE SHELL" - funny or not so?!
There are some chemical reactions that occur spontaneously when reactants are mixed. In this case, rather dangerous mixtures are formed that can explode, ignite or poison. Here is one of them!
Strange phenomena were observed in some American and English clinics. From time to time, sounds resembling pistol shots were heard from the sinks, and in one case the drain pipe suddenly exploded. Fortunately, no one was hurt. The investigation showed that the culprit was a very weak (0.01%) sodium azide NaN 3 solution, which was used as a preservative for saline solutions.
Excess azide solution was poured into the sinks for many months or even years - sometimes up to 2 liters per day.
By itself, sodium azide - a salt of hydroazide acid HN 3 - does not explode. However, azides of heavy metals (copper, silver, mercury, lead, etc.) are very unstable crystalline compounds that explode upon friction, impact, heating, and exposure to light. An explosion can occur even under a layer of water! Lead azide Pb (N 3) 2 is used as an initiating explosive, which undermines the main mass of explosives. For this, only two tens of milligrams of Pb (N 3) 2 are enough. This compound is more explosive than nitroglycerin, and the speed of detonation (propagation of an explosive wave) during an explosion reaches 45 km / s - 10 times greater than that of TNT.
But where could heavy metal azides come from in clinics? It turned out that in all cases, the drain pipes under the sinks were made of copper or brass (such pipes bend easily, especially after heating, so they are convenient to install in the drain system). The sodium azide solution poured into the sinks, flowing through such tubes, gradually reacted with their surface, forming copper azide. I had to change the tubes to plastic ones. When such a replacement was carried out in one of the clinics, it turned out that the removed copper tubes were heavily clogged with solid matter. The specialists who were engaged in "mine clearance", in order not to take risks, blew up these tubes on the spot, folding them into a metal tank weighing 1 ton. The explosion was so strong that it moved the tank several centimeters!
Physicians were not very interested in the nature of the chemical reactions leading to the formation of explosives. No description of this process has been found in the chemical literature either. But it can be assumed, based on the strong oxidizing properties of HN 3, that such a reaction took place: the N-3 anion, oxidizing copper, formed one N2 molecule and a nitrogen atom, which became part of ammonia. This corresponds to the reaction equation: 3NaN 3 +Cu + 3H 2 O → Cu(N 3) 2 + 3NaOH + N 2 +NH 3.
Everyone who deals with soluble metal azides, including chemists, has to reckon with the danger of a bomb forming in a sink, since azides are used to obtain highly pure nitrogen, in organic synthesis, as a blowing agent (foaming agent for the production of gas-filled materials: foam plastics, porous rubber, etc.). In all such cases, it must be ensured that the drain pipes are plastic.
Relatively recently, azides have found a new application in the automotive industry. In 1989, airbags appeared in some models of American cars. Such a pillow containing sodium azide is almost invisible when folded. In a head-on collision, the electric fuse leads to a very rapid decomposition of the azide: 2NaN 3 =2Na+3N 2 . 100 g of powder release about 60 liters of nitrogen, which in about 0.04 s inflates the pillow in front of the driver's chest, thereby saving his life.
Many processes without which it is impossible to imagine our life (such as respiration, digestion, photosynthesis and the like) are associated with various chemical reactions of organic compounds (and inorganic ones). Let's look at their main types and dwell in more detail on the process called connection (attachment).
What is called a chemical reaction
First of all, it is worth giving a general definition of this phenomenon. The phrase under consideration refers to various reactions of substances of varying complexity, as a result of which products different from the original ones are formed. The substances involved in this process are referred to as "reagents".
In writing, the chemical reaction of organic compounds (and inorganic ones) is written using specialized equations. Outwardly, they are a bit like mathematical examples of addition. However, instead of an equal sign ("="), arrows ("→" or "⇆") are used. In addition, there can sometimes be more substances on the right side of the equation than on the left. Everything before the arrow is the substances before the start of the reaction (left side of the formula). Everything after it (the right side) is the compounds formed as a result of the chemical process that has taken place.
As an example of a chemical equation, we can consider water into hydrogen and oxygen under the influence of an electric current: 2H 2 O → 2H 2 + O 2. Water is the initial reactant, and oxygen and hydrogen are the products.
As another, but more complex example of a chemical reaction of compounds, we can consider a phenomenon familiar to every housewife who has baked sweets at least once. We are talking about quenching baking soda with table vinegar. The ongoing action is illustrated using the following equation: NaHCO 3 +2 CH 3 COOH → 2CH 3 COONa + CO 2 + H 2 O. It is clear from it that in the process of interaction of sodium bicarbonate and vinegar, sodium salt of acetic acid, water and carbon dioxide are formed.
By its nature, it occupies an intermediate position between physical and nuclear.
Unlike the former, compounds participating in chemical reactions are able to change their composition. That is, from the atoms of one substance, several others can be formed, as in the above equation for the decomposition of water.
Unlike nuclear reactions, chemical reactions do not affect the nuclei of atoms of the interacting substances.
What are the types of chemical processes
The distribution of reactions of compounds by type occurs according to different criteria:
- Reversibility / irreversibility.
- Presence/absence of catalyzing substances and processes.
- By absorption / release of heat (endothermic / exothermic reactions).
- By the number of phases: homogeneous / heterogeneous and two hybrid varieties.
- By changing the oxidation states of the interacting substances.
Types of chemical processes in inorganic chemistry according to the method of interaction
This criterion is special. With its help, four types of reactions are distinguished: connection, substitution, decomposition (splitting) and exchange.
The name of each of them corresponds to the process that it describes. That is, they are combined, in substitution they change to other groups, in the decomposition of one reagent several are formed, and in the exchange the participants in the reaction change atoms among themselves.
Types of processes according to the method of interaction in organic chemistry
Despite the great complexity, the reactions of organic compounds occur according to the same principle as inorganic ones. However, they have somewhat different names.
So, the reactions of combination and decomposition are called “addition”, as well as “cleavage” (elimination) and directly organic decomposition (in this section of chemistry there are two types of splitting processes).
Other reactions of organic compounds are substitution (the name does not change), rearrangement (exchange) and redox processes. Despite the similarity of the mechanisms of their occurrence, in organic matter they are more multifaceted.
Chemical reaction of the compound
Having considered the various types of processes that substances enter into in organic and inorganic chemistry, it is worth dwelling in more detail on the compound.
This reaction differs from all the others in that, regardless of the number of reagents at its beginning, in the final they all combine into one.
As an example, we can recall the process of slaking lime: CaO + H 2 O → Ca (OH) 2. In this case, the reaction of the combination of calcium oxide (quicklime) with hydrogen oxide (water) occurs. As a result, calcium hydroxide (slaked lime) is formed and warm steam is released. By the way, this means that this process is really exothermic.
Compound reaction equation
Schematically, the process under consideration can be depicted as follows: A+BV → ABC. In this formula, ABV is the newly formed A - a simple reagent, and BV - a variant of a complex compound.
It is worth noting that this formula is also characteristic of the process of addition and connection.
Examples of the reaction under consideration are the interaction of sodium oxide and carbon dioxide (NaO 2 + CO 2 (t 450-550 ° C) → Na 2 CO 3), as well as sulfur oxide with oxygen (2SO 2 + O 2 → 2SO 3).
Several complex compounds are also able to react with each other: AB + VG → ABVG. For example, all the same sodium oxide and hydrogen oxide: NaO 2 + H 2 O → 2NaOH.
Reaction conditions in inorganic compounds
As was shown in the previous equation, substances of varying degrees of complexity can enter into the interaction under consideration.
In this case, for simple reagents of inorganic origin, redox reactions of the compound (A + B → AB) are possible.
As an example, we can consider the process of obtaining a trivalent. For this, a compound reaction is carried out between chlorine and ferum (iron): 3Cl 2 + 2Fe → 2FeCl 3.
If we are talking about the interaction of complex inorganic substances (AB + VG → ABVG), processes in them can occur, both affecting and not affecting their valency.
As an illustration of this, it is worth considering the example of the formation of calcium bicarbonate from carbon dioxide, hydrogen oxide (water) and white food coloring E170 (calcium carbonate): CO 2 + H 2 O + CaCO 3 → Ca (CO 3) 2. In this case, it has place a classical coupling reaction. During its implementation, the valency of the reagents does not change.
A slightly more perfect (than the first) chemical equation 2FeCl 2 + Cl 2 → 2FeCl 3 is an example of a redox process in the interaction of simple and complex inorganic reagents: gas (chlorine) and salt (iron chloride).
Types of addition reactions in organic chemistry
As already mentioned in the fourth paragraph, in substances of organic origin, the reaction in question is called "addition". As a rule, complex substances with a double (or triple) bond take part in it.
For example, the reaction between dibrom and ethylene, leading to the formation of 1,2-dibromoethane: (C 2 H 4) CH 2 \u003d CH 2 + Br 2 → (C₂H₄Br₂) BrCH 2 - CH 2 Br. By the way, signs similar to equals and minus ("=" and "-") in this equation show the bonds between the atoms of a complex substance. This is a feature of writing formulas of organic substances.
Depending on which of the compounds act as reagents, several varieties of the addition process under consideration are distinguished:
- Hydrogenation (hydrogen molecules H are added along the multiple bond).
- Hydrohalogenation (hydrogen halide is added).
- Halogenation (addition of halogens Br 2 , Cl 2 and the like).
- Polymerization (formation from several low molecular weight compounds of substances with high molecular weight).
Examples of addition reactions (compounds)
After listing the varieties of the process under consideration, it is worth learning in practice some examples of the compound reaction.
As an illustration of hydrogenation, one can pay attention to the equation for the interaction of propene with hydrogen, as a result of which propane will appear: (C 3 H 6) CH 3 -CH \u003d CH 2 + H 2 → (C 3 H 8) CH 3 -CH 2 -CH 3 .
In organic chemistry, a compound (addition) reaction can occur between hydrochloric acid and ethylene to form chloroethane: (C 2 H 4 ) CH 2 = CH 2 + HCl → CH 3 - CH 2 -Cl (C 2 H 5 Cl). The equation presented is an example of hydrohalogenation.
As for halogenation, it can be illustrated by the reaction between dichlor and ethylene leading to the formation of 1,2-dichloroethane: (C 2 H 4 ) CH 2 = CH 2 + Cl 2 → (C₂H₄Cl₂) ClCH 2 -CH 2 Cl.
Many useful substances are formed due to organic chemistry. The reaction of connection (attachment) of ethylene molecules with a radical polymerization initiator under the influence of ultraviolet is a confirmation of this: n CH 2 \u003d CH 2 (R and UV light) → (-CH 2 -CH 2 -) n. The substance formed in this way is well known to every person under the name of polyethylene.
Various types of packaging, bags, dishes, pipes, insulation materials and much more are made from this material. A feature of this substance is the possibility of its recycling. Polyethylene owes its popularity to the fact that it does not decompose, which is why environmentalists have a negative attitude towards it. However, in recent years, a way has been found to safely dispose of polyethylene products. For this, the material is treated with nitric acid (HNO 3). After that, certain types of bacteria are able to decompose this substance into safe components.
The reaction of connection (addition) plays an important role in nature and human life. In addition, it is often used by scientists in laboratories to synthesize new substances for various important studies.
DEFINITION
Chemical reaction called the transformation of substances in which there is a change in their composition and (or) structure.
Most often, chemical reactions are understood as the process of transformation of initial substances (reagents) into final substances (products).
Chemical reactions are written using chemical equations containing the formulas of the starting materials and reaction products. According to the law of conservation of mass, the number of atoms of each element in the left and right sides of the chemical equation is the same. Usually, the formulas of the starting substances are written on the left side of the equation, and the formulas of the products are written on the right. The equality of the number of atoms of each element in the left and right parts of the equation is achieved by placing integer stoichiometric coefficients in front of the formulas of substances.
Chemical equations may contain additional information about the features of the reaction: temperature, pressure, radiation, etc., which is indicated by the corresponding symbol above (or “under”) the equals sign.
All chemical reactions can be grouped into several classes, which have certain characteristics.
Classification of chemical reactions according to the number and composition of the initial and resulting substances
According to this classification, chemical reactions are divided into reactions of combination, decomposition, substitution, exchange.
As a result compound reactions from two or more (complex or simple) substances, one new substance is formed. In general, the equation for such a chemical reaction will look like this:
For example:
CaCO 3 + CO 2 + H 2 O \u003d Ca (HCO 3) 2
SO 3 + H 2 O \u003d H 2 SO 4
2Mg + O 2 \u003d 2MgO.
2FeCl 2 + Cl 2 = 2FeCl 3
Combination reactions are in most cases exothermic, i.e. flow with the release of heat. If simple substances are involved in the reaction, then such reactions are most often redox (ORD), i.e. occur with a change in the oxidation states of the elements. It is impossible to say unequivocally whether the reaction of a compound between complex substances can be attributed to OVR.
Reactions in which several other new substances (complex or simple) are formed from one complex substance are classified as decomposition reactions. In general, the equation for a chemical decomposition reaction will look like this:
For example:
CaCO 3 CaO + CO 2 (1)
2H 2 O \u003d 2H 2 + O 2 (2)
CuSO 4 × 5H 2 O \u003d CuSO 4 + 5H 2 O (3)
Cu (OH) 2 \u003d CuO + H 2 O (4)
H 2 SiO 3 \u003d SiO 2 + H 2 O (5)
2SO 3 \u003d 2SO 2 + O 2 (6)
(NH 4) 2 Cr 2 O 7 \u003d Cr 2 O 3 + N 2 + 4H 2 O (7)
Most decomposition reactions proceed with heating (1,4,5). Decomposition by electric current is possible (2). The decomposition of crystalline hydrates, acids, bases and salts of oxygen-containing acids (1, 3, 4, 5, 7) proceeds without changing the oxidation states of the elements, i.e. these reactions do not apply to OVR. OVR decomposition reactions include the decomposition of oxides, acids and salts formed by elements in higher oxidation states (6).
Decomposition reactions are also found in organic chemistry, but under other names - cracking (8), dehydrogenation (9):
C 18 H 38 \u003d C 9 H 18 + C 9 H 20 (8)
C 4 H 10 \u003d C 4 H 6 + 2H 2 (9)
At substitution reactions a simple substance interacts with a complex one, forming a new simple and a new complex substance. In general, the equation for a chemical substitution reaction will look like this:
For example:
2Al + Fe 2 O 3 \u003d 2Fe + Al 2 O 3 (1)
Zn + 2HCl = ZnCl 2 + H 2 (2)
2KBr + Cl 2 \u003d 2KCl + Br 2 (3)
2KSlO 3 + l 2 = 2KlO 3 + Cl 2 (4)
CaCO 3 + SiO 2 \u003d CaSiO 3 + CO 2 (5)
Ca 3 (RO 4) 2 + ZSiO 2 = ZCaSiO 3 + P 2 O 5 (6)
CH 4 + Cl 2 = CH 3 Cl + Hcl (7)
Substitution reactions are mostly redox reactions (1 - 4, 7). Examples of decomposition reactions in which there is no change in oxidation states are few (5, 6).
Exchange reactions called the reactions that occur between complex substances, in which they exchange their constituent parts. Usually this term is used for reactions involving ions in aqueous solution. In general, the equation for a chemical exchange reaction will look like this:
AB + CD = AD + CB
For example:
CuO + 2HCl \u003d CuCl 2 + H 2 O (1)
NaOH + HCl \u003d NaCl + H 2 O (2)
NaHCO 3 + HCl \u003d NaCl + H 2 O + CO 2 (3)
AgNO 3 + KBr = AgBr ↓ + KNO 3 (4)
CrCl 3 + ZNaOH = Cr(OH) 3 ↓+ ZNaCl (5)
Exchange reactions are not redox. A special case of these exchange reactions is neutralization reactions (reactions of interaction of acids with alkalis) (2). Exchange reactions proceed in the direction where at least one of the substances is removed from the reaction sphere in the form of a gaseous substance (3), a precipitate (4, 5) or a poorly dissociating compound, most often water (1, 2).
Classification of chemical reactions according to changes in oxidation states
Depending on the change in the oxidation states of the elements that make up the reactants and reaction products, all chemical reactions are divided into redox (1, 2) and those occurring without changing the oxidation state (3, 4).
2Mg + CO 2 \u003d 2MgO + C (1)
Mg 0 - 2e \u003d Mg 2+ (reductant)
C 4+ + 4e \u003d C 0 (oxidizing agent)
FeS 2 + 8HNO 3 (conc) = Fe(NO 3) 3 + 5NO + 2H 2 SO 4 + 2H 2 O (2)
Fe 2+ -e \u003d Fe 3+ (reductant)
N 5+ + 3e \u003d N 2+ (oxidizing agent)
AgNO 3 + HCl \u003d AgCl ↓ + HNO 3 (3)
Ca(OH) 2 + H 2 SO 4 = CaSO 4 ↓ + H 2 O (4)
Classification of chemical reactions by thermal effect
Depending on whether heat (energy) is released or absorbed during the reaction, all chemical reactions are conditionally divided into exo - (1, 2) and endothermic (3), respectively. The amount of heat (energy) released or absorbed during a reaction is called the heat of the reaction. If the equation indicates the amount of released or absorbed heat, then such equations are called thermochemical.
N 2 + 3H 2 = 2NH 3 +46.2 kJ (1)
2Mg + O 2 \u003d 2MgO + 602.5 kJ (2)
N 2 + O 2 \u003d 2NO - 90.4 kJ (3)
Classification of chemical reactions according to the direction of the reaction
According to the direction of the reaction, there are reversible (chemical processes, the products of which are able to react with each other under the same conditions in which they are obtained, with the formation of starting substances) and irreversible (chemical processes, the products of which are not able to react with each other with the formation of starting substances ).
For reversible reactions, the equation in general form is usually written as follows:
A + B ↔ AB
For example:
CH 3 COOH + C 2 H 5 OH ↔ H 3 COOS 2 H 5 + H 2 O
Examples of irreversible reactions are the following reactions:
2KSlO 3 → 2KSl + ZO 2
C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O
Evidence of the irreversibility of the reaction can serve as the reaction products of a gaseous substance, a precipitate or a low-dissociating compound, most often water.
Classification of chemical reactions by the presence of a catalyst
From this point of view, catalytic and non-catalytic reactions are distinguished.
A catalyst is a substance that speeds up a chemical reaction. Reactions involving catalysts are called catalytic. Some reactions are generally impossible without the presence of a catalyst:
2H 2 O 2 \u003d 2H 2 O + O 2 (MnO 2 catalyst)
Often, one of the reaction products serves as a catalyst that accelerates this reaction (autocatalytic reactions):
MeO + 2HF \u003d MeF 2 + H 2 O, where Me is a metal.
Examples of problem solving
EXAMPLE 1
1. What reactions are called exchange reactions? How do they differ from the reactions of combination, decomposition and substitution?
Exchange reactions are reactions in which two complex substances exchange their constituent parts. Thus, complex substances are formed from complex substances. While in decomposition reactions, several simple or complex substances are formed from one complex substance, in compound reactions, one complex substance is formed from several simple or complex substances, in substitution reactions, one complex and one simple substance is formed from one simple and one complex substance.
2. Can it be argued that the interaction of a carbonate solution of any metal and an acid is only an exchange reaction? Why?
3. Write the equations for the exchange reactions between solutions:
a) calcium chloride and sodium phosphate;
b) sulfuric acid and iron (III) hydroxide. 
4. Which of the exchange reactions, the schemes of which 
will run to the end? To answer, use the table of solubility of hydroxides and salts in water. 
5. Determine the amount of sodium hydroxide substance that will be required to completely neutralize 980 g of a 30% phosphoric acid solution. 
6. Calculate the amount of the substance and the mass of the precipitate formed during the interaction of 980 g of a 20% solution of copper (II) sulfate with the required amount of potassium hydroxide. 
Part I
1. Connection reactions are"chemical antonym" of the decomposition reaction.
2. Write down the signs of the compound reaction:
- 2 simple or complex substances participate in the reaction;
- one complex is formed;
- heat is released.
3. Based on the selected features, give a definition of the reactions of the compound.
Combination reactions are reactions that result in the formation of one complex substance from one or more simple or complex substances.
According to the direction of the reaction, they are divided into:
Part II
1. Write down the equations of chemical reactions:
2. Write the equations of chemical reactions between chlorine:
1) and sodium 2Na+Cl2=2NaCl
2) and calcium Ca+Cl2=CaCl2
3) and iron to form iron (III) chloride 2Fe+3Cl2=2FeCl3
3. Describe the reaction
4. Describe the reaction
5. Write down the equations of the compound reactions proceeding according to the schemes:
6. Arrange the coefficients in the reaction equations, the schemes of which are:
7. Are the following statements correct?
A. Most compound reactions are exothermic.
B. As the temperature rises, the rate of a chemical reaction increases.
1) both statements are correct
8. Calculate the volume of hydrogen and mass of sulfur required to form 85 g of hydrogen sulfide.
