Why is there more than one trim method for a chemical equation?

It is present in complex chemical reactions.

For example, complex redox reactions.

There are many elements involved in redox, resulting in multiple methods to make the electron loss the same.

Even last time, I saw a A element increase by 2 valence, B element by 6 valence, and C element by 5 valence. (I can't remember exactly, so let's use ABC instead).

From the equilibrium of electrons, it can be 2a+b=2c and later my classmate came up with an a+3b=4c

Put the whole equation.

Trim discovery is OK.

Mathematically, it's a bit like a multivariate indefinite equation.

There are multiple solutions the same.

As for the other types of reactions, I don't know how to explain them.

That chemical equilibrium is the sum of 2 chemical reaction equations.

If the coefficients are disproportionate, they can indeed be balanced, but one of them must be wrong, and it is recommended to verify it with electron conservation.

Trim is also generally conserved with electrons.

This phenomenon can occur in complex redox reactions.

Suppose only one substance accepts electrons, but there are multiple substances (i.e., reducing agents) that give the idea.

The difference in the proportions of these two substances may cause different coefficients

Have you simplified it after leveling? For example, the coefficient after trim is.

1. Observation method: This method often works for some simple equations. In fact, even if the number is purposefully made up for balancing, there are often factors such as odd and even. This method is likely to work for any kind of equation.

2. Charge balance method: This method is most useful for ion equations. In the ionic equation, except for insoluble substances, gases, and water, everything else is written in ionic form, and the charges at both ends of the equation are equalized first, and then the observation method is used to balance water, gas, etc.

This method generally does not miss. But it's too good for redox equations.

3. Redox method: This method is for the redox equation. Remember here: "The valency rises and loses the redox agent". The corresponding is "reducing the valency to obtain a reducing oxidant". The specific usage is:

1) Mark the valency of the element in the upper part of the element where the valency of the element changes, and distinguish whose is higher and whose is lower.

2) Connect the same elements with lines to find and mark the number of higher charges or the number of lower charges.

3) Find the least common multiple and multiply it by the number of charges that increase or decrease, respectively.

4) Trim: Write the least common multiple of each before their respective chemical formulas (i.e., coefficients). And pay attention to whether these elements with valency changes are equal before and after the chemical change, and in general, if they are not equal, they are integer multiples.

5) Cooperate with the observation method to balance other good things such as water and insoluble matter generated.

01 The balancing methods of chemical equations include: least common multiple method, odd-even balancing method, observation balancing method, electron gain and loss method, and normalization method.

Chemical equation trim is a way of calculating chemical equations. The chemical reaction equation strictly adheres to the law of conservation of mass, and after writing the chemical reaction equation and writing the reactants and products, the number of atoms on the left and right sides is often not equal, and the law of conservation of mass is not satisfied, which needs to be solved by calculating the balance.

1. Least common multiple method: This method is suitable for common chemical equations with little difficulty.

2. Odd-even trim method: This method is suitable for multiple occurrences of an element on both sides of the chemical equation, and the total number of atoms of the element on both sides is odd and even.

3. Observation method balancing: Sometimes there will be a substance with a complex chemical formula in the equation, and we can deduce the coefficients of other chemical formulas through this complex molecule.

4. Electron gain and loss method: In the redox reaction, the total number of electrons lost by the reducing agent must be equal to the total number of electrons gained by the oxidant. According to this rule, the redox reaction equation can be leveled.

5. Normalization method: find the key chemical formula in the chemical equation, set the number before the chemical formula as 1, and then balance the stoichiometric number before the other chemical formula according to the key chemical formula. If the measured number is a fraction, and then the measured number is multiplied by the same integer, and the fraction is turned into an integer, this balancing method in which the key chemical formula measurement number is 1 is predetermined, which is called the normalization method.

This method is suitable for common chemical equations that are not very difficult. For example, kclo3

KCl+O2 In this reaction the number of oxygen atoms on the right is 2 and the left is 3, then the least common multiple is 6, so Kclo3

The former coefficient should be matched with 2, o2

With 3 in front, the formula becomes: 2kclo3

KCl+3O2, since the number of potassium atoms and chlorine atoms on the left becomes 2, the coefficient of 2 should be matched before KCL, ** is changed to equal sign, and the condition is indicated: 2kclo3

2kcl+3o2

Formula: Appear the most odd number, and then turn the odd number into even. Observe the parity and rationale, two or four do not work, and then seek six.

The most odd number appears, and then the odd number becomes even. These two sentences speak of the first step in the odd spouse method. "The most odd occurrences" means that the element that appears the most before and after the reaction is looked for in the reaction formula, and then on this basis, the number of atoms is the odd number of the term.

"Turning the odd number into even" means multiplying an even number before the odd number found (usually the smallest even number 2 in front of the numerator).

Observe the parity and rationale, two or four do not work, and then seek six. This method is suitable for multiple occurrences of an element on both sides of a chemical equation where the total number of atoms of that element on both sides is odd and even. Example and caution: C2H2O2

CO2H2O, the balance of this equation starts with the oxygen atom that appears the most first. o2

There are 2 oxygen atoms in it, and the total number of oxygen atoms should be even, regardless of the coefficient before the chemical formula. Hence h2 on the right

o should be assigned a coefficient of 2 (or 4 if other molecular coefficients appear as fractions), from which c2 is inferred

H2 before 2, the formula becomes: 2C2H2O2

co22h2

o, from which CO2 can be known

The former coefficient should be 4, and the last is with elemental O2

is 5, and the condition can be specified: 2c2h25o2

4co22h2

o。A method for judging the stoichiometric number of a substance by analyzing the chemical formula of a substance.

For example: trim Fe2

o3co→fe+co2

In the reaction, each CO binds to an oxygen atom to form CO2

molecule, and Fe2

O3 donates three oxygen atoms at once, so three CO molecules must accept these three oxygen atoms to form three CO2

The molecule is Fe2

o33co→fe+3co2

Finally, the trim equation FE2

o33co=2fe+3co2

This trimming method analyzes Fe2 by observation

The number of oxygen atoms in the O3 chemical formula determines the stoichiometric number of CO, so it is called the observation method.

The method of trimming the chemical equation is as follows:

1. Fractional balancing method: the "universal balancing method" of chemical reaction equations with elemental participation in the reaction or elemental generation, that is, the atoms of the "elemental" elements in the chemical equation are first balanced, and finally the appropriate fractional balancing of the "elemental" element atoms is added.

2. Least common multiple method: find the elements that appear once on the left and right sides and have a large change in atomic number; Find the least common multiple of the number of atoms of the element; Divide the least common multiple by the number of atoms in each case, and the resulting value is the measurement number of the corresponding substance.

3. Determine the "1" method: start with the chemical formula with complex composition or atomic number, and make the measurement number "1"; Derive other chemical formula measurements.

4. Odd-even balancing method: an element appears more often in the formula, and the total number of atoms at each end is one odd and one even. The element is selected as the starting point for the trim, the odd number is changed to the smallest even number (i.e. multiplied by 2), and then the metrology of the other chemical formulas is determined.

5. Observation method: deduce the stoichiometric number of the chemical formula of the reactant and the stoichiometric number of the product from a product with a more complex chemical formula, and then find out the dumping stoimetric number of other chemical formulas according to the stoichiometric number of the obtained chemical formula, so that it can be balanced.

The trim method for chemical equations is as follows:

Generally, atoms with complex atomic numbers are matched, such as oxygen atoms, you can start with oxygen atoms.

For example, in the first step, the least common multiple of the iron atom is 3, the least common multiple of the oxygen atom is 12, and the least common multiple of the aluminum atom is 2. So start with oxygen.

In the second step, the coefficient of Fe3O4 is 12 4 3, and the coefficient of Al2O3 = 12 3 = 4.

In the third step, the coefficients of Al and Fe are determined according to the coefficients of Fe3O4 and Al2O3.

NoteNotes:

1. Write the reaction conditions in the chemical equation. The general ones are marked with δ above the equal sign. Trim coefficients are mostly not fractions (except for reductions between them).

2. The reaction that can be carried out at room temperature and pressure, no need to write conditions; However, if the experiment in the title has a specific condition, it is always marked with that specific condition (e.g., heating).

3. When reacting to a single condition, the condition is written above; If there are two or more conditions, what cannot be written above is written below; When there is both a catalyst and other reaction conditions, the catalyst is always written on it.

1.Observational basis.

2.Lcm.

3.Parity.

4.Establish a law.

5.Fractional balancing method.

6.Pending coefficient method.

1.The observation method is based on the atoms of reactants and products, that is, the balancing is mainly based on the conservation of materials, which typically represents the combustion of iron and oxygen and the production of oxygen by potassium permanganate.

2.The least common multiple is also mainly based on the conservation of the material, for example, the reactant has two oxygen atoms, and the product has five oxygen atoms, and the least common multiple is ten.

3.For example, if water is electrically decomposed into hydrogen and oxygen, then the oxygen atoms produced are an even number, and the reactants are an odd number of oxygen atoms, so the reactant water has to be multiplied by two to become an even number.

4.The method of determining one is to select one compound of a reactant first, try not to choose the element, and the element is the last. The reactants are leveled according to the conservation of materials according to the compounds that are normalized.

5.Fractional Equalization Method If you really don't match sometimes, you can use fractions and then amplify them at the end.

6.The undetermined coefficient method sets the unknowns, and establishes the equation to solve the equation according to the number and type of atoms before and after the reaction.