How do you balance the chemical formula of the first 3 chemical formula? How to write a chemical for

Use the valence to raise and fall equally! There is also charge balancing. It's hard to say, I have to wait for a demonstration to show you, it's hard to understand just by talking about it.

If it is not a redox reaction, the number of atoms is equal, if so, the elements whose valency has changed are marked first, and then how much they have changed, and then their least common multiple is calculated, and then multiplied by the least common multiple, the match is equal, and then according to the atom equality, the others are matched.

1.Basic copper carbonate is decomposed by heat.

Cu2(OH)2CO3== ==2CuO+H2O+CO22 potassium permanganate to oxygen.

2kmNO4== ==K2mNO4+MNO2+O2 3 potassium chloride and manganese dioxide are mixed to produce oxygen.

2kclo3==mno2, ==2kcl+3o2 4 hydrogen peroxide to produce oxygen.

2H2O2==Mno2==2H2O+O2 5 Iron reacts with copper sulfate solution.

fe+cuso4==feso4+cu

6. Sodium carbonate reacts with dilute hydrochloric acid.

na2co3+2hcl==2nacl+h2o+co2↑

An introduction to the trim method for chemical equations.

One. Least common multiple method.

Applicable conditions: The matching atom appears only once on the left and right sides of the equation.

Example 1Trim:

Analysis: First, according to the least common multiple of the number of oxygen atoms on both sides is 12, the coefficient that can be determined is 3, and the coefficient is 4. It was further determined that the coefficient for aluminum is 8 and the coefficient for iron is 9.

As a result. Two. Odd Spouse Method.

Applicable conditions: The odd number of atoms of the element in the equation appears only once.

Example 2Trim:

Analysis: In the equation, only the number of oxygen atoms in water is odd, and the coefficient is matched to 2 first. The coefficient determined according to the number of hydrogen atoms is 2, and the final coefficient is 1.

The trim result is.

Three. Establish a law.

Applicable conditions: such as the reaction of most hydrocarbons or compounds containing hydrocarbon and oxygen with oxygen, as well as certain decomposition reactions.

Example 3Trim:

Analysis: The coefficient is set to 1, and then the coefficient of CO2 is determined to be 2, and the coefficient of H2O is 3. The total number of oxygen atoms on the right side of the equation is 7, and there is one oxygen atom in it, which determines that the factor of O2 is 3.

Deserved the result.

Four. Algebraic method (also known as the undetermined coefficient method).

Applicable conditions: There are many types of reactants or products, and the trim does not know where to start with the more complex reactions.

Example 4Trim:

Analysis: It can be assumed that the trim factors of the sum and the front are x and y respectively, and then the trim sum is thus made. Ready.

Hypothesis) Hypothesis).

MN conservation) (o conservation).

From the conservation of k elements (i.e., the number of k atoms on both sides of the equation should be equal), it is obtained: . So, at that time, then. Substituting the reaction equation of the above undetermined coefficients, the balancing result is .

From the above, it can be seen that there is a law for balancing, but there is no definite law. For the same reaction equation, different methods may be used to balance, and sometimes even several methods may be used at the same time. This requires us to practice a lot before practice makes perfect.

Trimming a chemical reaction is all about balancing the material and charge on both sides of the equation. For example, there are two ways to trim redox chemical equations:

1) Oxidation number rise and fall method: first mark the elements with increased oxidation number (increase in price), then mark the elements with reduced oxidation number (decrease in price), and finally make the oxidation number rise and fall value of the reaction equal according to the least common multiple method.

2) Ion-electron method: first match the material and charge on the left and right sides of the semi-reaction of the oxidant, then match the material and charge on the left and right sides of the semi-reaction of the reducing agent, and finally make the number of electrons gained and lost in the reaction equal according to the least common multiple method.

According to the conservation of mass, the number of atoms on the left and right sides of the equal sign is equal.

Isn't it in the book...

1 is the least common multiple and 2 is the odd spouse.

You have to see the essence of the question, and you will no longer be afraid of the same problem in the future.

The essence of chemical reaction is the cause of the gain and loss of electrons, that is, the transfer of electrons between different substances occurs, but the electrons will not disappear or increase out of thin air, so how much you lose must also get how much you know this, and then use the least common multiple method to calculate the equality of the valence on both sides of the equal sign, you can do the problem, the method is the characterization of the electron gain and loss.

However, the electronic method of gain and loss may be a little unfamiliar to junior high school students, but it should be within the scope of understanding.

4Al+3O2--- ignite the silver hunger to do the front balance---2Al2O32kclo3---mNo2--- ignition ---2kCl + 3O2 ch4+ 2O2--- ignition ---CO2 + 2H2O2Al + Fe2O3--- point limb air combustion --- Al2O3 + 2Fe