Principles and conditions of the four basic chemical reactions in high school chemistry

Chemical reaction: A reaction in which two or more substances produce another substance, called a chemical reaction.

Decomposition reaction: A chemical reaction in which two or more other substances are produced from one substance is called a decomposition reaction.

Displacement reaction: The reaction of one element and one compound to produce another element and another compound is called a displacement reaction.

Metathesis reaction: The reaction in which two compounds exchange components with each other to form two other compounds, which is called metathesis reaction.

There are 4 types of displacement reactions:

A more reactive metal replaces a less reactive metal or hydrogen, such as:

fe+cuso4=cu+feso4

zn+2hcl=h2↑+zncl2

The more reactive non-metals replace the less reactive non-metals, such as:

cl2+2nabr=br2+2nacl

o2+2h2s=2s↓+2h2o

Non-metals are replaced by metals, metals are replaced by non-metals, and the conditions for the metathesis reaction to occur: (the following conditions are met at the same time).

1) Reactants: must be soluble (including soluble acids).

2) Product: There must be precipitation or gas or water or weak electrolyte (e.g., NaAC+HCl=NaCl+HAC).

Chemical reaction: A reaction in which a variety of substances are produced to produce a single substance.

Decomposition reaction: A reaction in which one substance produces multiple substances.

Displacement reaction: A reaction in which an element reacts with a compound to produce a reaction of a single element and a compound.

Metathesis reaction: A reaction in which two compounds exchange components with each other to form two other compounds.

The conditions for the metathesis reaction to occur: 1. Generate gas.

2. Generate precipitation.

3. There is the generation of substances that are difficult to ionize.

Chemical reactions can be classified into four basic reaction types: chemical reactions, decomposition reactions, displacement reactions, and metathesis reactions.

Chemical reaction: A reaction in which two or more substances produce another substance, called a chemical reaction.

a+b=c decomposition reaction: a chemical reaction in which two or more other substances are generated from one substance, which is called a decomposition reaction. a=b+c

Displacement reaction: The reaction in which one element reacts with another compound to form another element and compound is called a displacement reaction. a+bc=ac +b

Metathesis reaction: The reaction in which two compounds exchange ions with each other to form two other compounds is called metathesis reaction. ab+cd=ad +cb

The basic types of reactions in chemical reactions are:

Chemical reactions, decomposition reactions, metathesis reactions, and displacement reactions.

In addition, there is a redox reaction (the displacement reaction is a redox reaction, and the metathesis reaction must not be a redox reaction).

Oxidation reaction, synthesis reaction, decomposition reaction, reduction reaction.

This topic examines the problem of hydrolysis of weak acid roots.

In a mixed solution of sodium carbonate and sodium bicarbonate, the following reflections are present:

na2co3=2na++co32-nahco3=na++hco3-

CO32-+H+=(reversible) HCO3-

HCO3 - +H+ = (reversible) H2CO3

H2O = (reversible) H++OH-

First of all, let's be clear: sodium carbonate and sodium bicarbonate are of the same concentration, and they are both equally completely ionized. The above hydrolyzed HCO3- is partly from the ionization of sodium bicarbonate and partly from the hydrolysis of CO32-.

Problem solving: Suppose C (sodium carbonate) = C (sodium bicarbonate) = X The CO32- concentration consumed in the reaction "CO32-+H+= (reversible) HCO3-" is A, and the HCO3- concentration consumed in the reaction "HCO3-+H+= (reversible) H2CO3" is B. Then there is the following relationship: c(na+)=3xc(CO32-)=x-ac(HCO3-)=a+x-bc(oh-)=c(h+)+a+bc(h2co3)=b

Calculate 3 [C(CO32-)+C(HCO3-)+C(H2CO3)]=6x, so C is the correct answer.

2C(CO32-)+C(HCO3-)+C(OH-)=3X+C(H+)So DThe answer is correct.

Obviously the answer is incorrect.

The degree of hydrolysis in the first step of CO32- is much greater than that of the second step, although HCO3- in the solution has two **, but we can still think that A is greater than BC(CO32-)-C(HCO3-)=B-2A is less than 0, so the answer to B is also correct.

The answer is BCD

This topic examines the problem of hydrolysis of weak acid roots.

At. Sodium carbonate.

And. Sodium bicarbonate.

The following reflection is present in the mixed solution:

na2co3

2na+co32-

nahco3

na+hco3-

co32-h+

reversible) HCO3-

hco3-h+

reversible) H2CO3

H2O (reversible) H+

OH- First of all, it is clear that sodium carbonate and sodium bicarbonate are of the same concentration, and they are both equally completely ionized.

And above hydrolyzed HCO3-

Part of it comes from the ionization of sodium bicarbonate and part of it comes from the hydrolysis of CO32-.

Problem solving: Suppose C (sodium carbonate) = C (sodium bicarbonate) = X in the reaction "CO32-

H+ (reversible) HCO3-" consumes CO32- at a concentration of A in the reaction "HCO3-

H+ (reversible) H2CO3

The concentration of HCO3- consumed in is B.

Then there is the following relation: c(na+)=3x

c(co32-)=x-a

c(hco3-)=a+x-b

c(oh-)=c(h+)+a+b

c(h2co3)=b

Calculate 3[C(CO32-)+C(HCO3-)+C(H2CO3)]=6x

So the answer is correct.

2C(CO32-)+C(HCO3-)+C(OH-)=3X+C(H+)So DThe answer is correct.

Obviously the answer is incorrect.

CO32 - the first step.

Degree of hydrolysis. It is much larger than the second step of hydrolysis, although HCO3- in the solution has two **, but we can still consider A to be greater than B

c(co32-)

c(hco3-)=b-2a

Less than 0 so b the answer is also correct.

The answer is BCD

1: Organic reactions:

Addition reaction (after the addition reaction is carried out, the heavy bond collapses or opens, and the atoms at both ends of the original heavy bond are connected to a new group).

Elimination reaction (a reaction in which an organic compound removes a small molecule (e.g., water, hydrogen halide, etc.) from one molecule under the right conditions to produce an unsaturated (double or triple bond) compound).

Substitution reactions (reactions in which an organic compound is attacked by a certain class of reagent, causing a group (or atom) in a molecule to be replaced by that reagent).

Polyaddition (monomers react with each other to form a polymer compound, called polyaddition).

Polycondensation reaction (a reaction in which two or more organic molecules interact and combine to form a macromolecule by covalent bonding while losing water or other relatively simple inorganic or organic molecules).

2: Inorganic reactions:

Decomposition reaction (refers to the reaction in which a compound is broken down into two or more simpler elements or compounds under specific conditions).

Chemical reaction (refers to the reaction of two or more substances to produce a new substance).

Metathesis reaction (a reaction in which two compounds exchange components with each other to produce two other compounds).

Displacement reaction (refers to the reaction of one element and one compound to produce another element and another compound).

3: Spontaneous reaction, non-spontaneous reaction.

4: Exothermic reaction, endothermic reaction.

5: Redox reaction (redox reaction is a chemical reaction in which the valency of a certain element changes before and after the reaction).

6: Ionic reaction (chemical reaction with the participation of ions).

7: Reversible reaction, irreversible reaction.

8: Isomerization reaction (oxygen to ozone, ozone to oxygen).

Note: The above are the main types of reactions, and there are many more to be specific.

For example, the neutralization reaction is actually a metathesis reaction, which is also an exothermic reaction and a spontaneous reaction.

Another example is the esterification reaction, which is actually a substitution reaction.

There are also sulfidation, nitrification, hydrolysis, combustion, dehydration, electrophilic reaction, nucleophilic reaction; Nitrification, halogenation, sulfonation, ammoniation, acylation, cyanidation and so on.

Just remember the basic types of reactions, and the rest just need to be understood.

One more point: a nuclear reaction is not a chemical reaction.

Redox reaction, which is the main thing. There are various conditions, and there are also electrode reactions, which are in galvanic cells and electrolytic cells

Well, in addition to what was said upstairs, there are additions, oxidation, polyadditions, and substitution ......These things are all in the chemistry bar - the paste bar.

Let the amount of substance to be converted by N2 be x.

N2 +3H2<*****==>2NH3 Start 0 Change x 3x 2X

2 min ( 2xmol after 2 min the total amount of gas is (

The volume fraction is equal to the quantity fraction of the substance because the volume is directly proportional to the amount of the substance.

2x (Solve x=.)

The concentration of the substance changed by N2 is C= N V=, the reaction rate is V= C, the amount of the substance reacted is 3X=3*, and the conversion rate is 2min, the concentration of N2, H2, and NH3 is K=C2(NH3) C(N2)*C3(H2)=(

n2 + 3h2 = 2nh3

Starting concentration: 0

Equilibrium concentration: 2x total concentration = 2x (, x=

Average reaction rate of n2 = molar liter seconds.

H2 conversion rate =

The equilibrium constant k=(2*.)

Answer: With the same concentration, the pH of the Na2CO3 solution is greater than the pH of NaHCO3.

Reason: Both carbonate ions and bicarbonate ions are hydrolyzed in solution.

And there are two steps of hydrolysis of carbonate ions, and the degree of hydrolysis is greater than that of bicarbonate ions. So the alkalinity of sodium carbonate solution is greater than that of sodium bicarbonate solution.

Know that carbonic acid and bicarbonate can be hydrolyzed Carbonate has a strong hydrolysis ability, so there are more hydroxides hydrolyzed, so the pH of the solution is greater than that of bicarbonate, and you can know it by comparing the degree of hydrolysis.

Sodium carbonate has a high pH because carbonate has a stronger hydrolytic capacity than bicarbonate because carbonate is more acidic than bicarbonate.