How to do chemistry is called writing out the chemical formula trim and then calculating, how to do

First, according to the redox equation, the electron equality coefficient is obtained and lost, and then according to the conservation of the material, if it is the ion equation, it is balanced according to the order of electrons, charge, and material.

According to the law of conservation of mass, the reaction before and after the reaction is balanced with each other.

It's the same number of atoms as each other!

Calculate again!

The problem is usually to say the reactants and the products, and you write them as chemical equations and then you do the trimming.

Final calculation.

It's about writing chemical equations.

Let's be clear, what do you say?

a) Least common multiple method.

This method is suitable for the common and less difficult chemical guessing equations. For example, in this reaction formula, the number of oxygen atoms on the right is 2, and the number of oxygen atoms on the left is 3, then the least common multiple is 6, so the coefficient before kclo3 should be matched with 2, and the coefficient before O2 should be matched with 3, and the formula becomes: 2kclo3 KCl+3O2, since the number of potassium atoms and chlorine atoms on the left becomes 2, then the coefficient 2 before KCL, ** is changed to equal sign, indicating the condition is:

2kclo3==2kcl+3o2↑

2) Odd-even equalization.

This method is suitable for the 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, for example: C2H2+O2-CO2+H2O, and the balance of this equation starts from the oxygen atom with the most occurrences first. There are 2 oxygen atoms in O2, and the total number of oxygen atoms should be even, regardless of the number of coefficients before the chemical formula.

Therefore, the coefficient of H2O on the right should be matched with 2 (if other molecular coefficients appear as fractions, it can be matched with 4), from which it can be deduced that the first 2 of C2H2 becomes: 2C2H2+O2==CO2+2H2O, from which it can be seen that the coefficient before CO2 should be 4, and the final coefficients with elemental O2 are 5, and the conditions can be specified:

2c2h2+5o2==4co2+2h2o

c) Observational balancing.

Sometimes there will be a substance with a more complex chemical formula in the equation, we can deduce the coefficients of other chemical formulas through this complex molecule, for example: Fe + H2O - Fe3O4 + H2, Fe3O4 chemical formula is more complex, obviously, Fe3O4 Fe** in the elemental Fe, O comes from H2O, then Fe is preceded by 3, H2O is preceded by 4, then the formula is: 3Fe + 4H2O Fe3O4 + H2 This deduces that the H2 coefficient is 4, indicating the conditions, ** Change to an equal sign:

3fe+4h2o==fe3o4+4h2↑

The trim methods for chemical formulas are: least common multiple method, observation method and pending coefficient method.

1. Writing formulas for chemical formulas.

Left reaction, right generation; Chemical formula, please write correctly; Measure the number to trim; Even the equal sign, the condition is clear; Mark the air and use the arrows.

2. Least common multiple method.

The least common multiple method is one of our most commonly used trim methods. Applicable conditions: The matching atom appears only once on the left and right sides of the equation, and this method is suitable for common chemical equations with little difficulty.

1. Find the element with the largest least common multiple of the number of atoms on both sides of **, and find its least common multiple.

2. According to the determined coefficients, match other coefficients, and check whether they are balanced.

3. Observation.

For observation, we start with the most complex compounds in this reaction.

Example: Fe2(SO4)3NaOH==Fe(OH)3Na2SO4

For this reaction, the most complex compound is Fe2(SO4)3, according to the conservation of elements, there are 3 for SO4 and 2 for Fe, so the coefficient of Na2SO4 is 3, the coefficient of Fe(OH)3 is 2, then NaOH is 6.

fe2(so4)3 6naoh=2fe(oh)3↓ 3na2so4。

Fourth, the method of pending coefficients.

1. Assume the coefficients of each chemical formula.

2. List the equations according to the law of conservation of mass.

3. Assume the relationship between the coefficients.

4. Convert each coefficient to the simplest ratio.

5. Check whether it is trimmed.

Also use this example.

For example: NH3+Cl2 - NH4Cl+N2

Let the stoichiometric numbers of each substance be a, b, c, and d.

ANH3+BCL2 – CNH4Cl+DN2 Column Equations A=C+2D (satisfying the equal number of nitrogen atoms) ANH3 has a nitrogen atom, CNH4Cl has C nitrogen atoms, DN2 has 2D nitrogen atoms, according to the principle of conservation of mass.

So a=c+2d (the number of atoms before and after is the same) and 3a=4c (the number of hydrogen atoms is equal).

AnH3 has a hydrogen atom and CNH4Cl has 4c hydrogen atom 2B=C (satisfying that the number of chlorine atoms is equal).

BCL2 has 2b chlorine atoms CNH4Cl has c chlorine atoms and then solves the quaternary system of linear equations.

Let b = 1, and the solution is: a = 8 3, c = 2, d = 1 3

The calculated answer is the trim factor, so.

8nh3+3cl2=6nh4cl+n2

Conservation of elements, that is, the number of all elements before and after the reaction is unchanged, like 4H2O+3Fe== Fe3O4+4H2 The number of Fe before and after the reaction is 3, the number of O is 4, and the number of H is 8.

Calculations are based on coefficients. Like the equation above, if there are 4 water and 3 iron reactions, 1 ferric tetroxide and 4 hydrogen will theoretically be formed (excluding impurities, environmental influences, etc.).

If there are 2 hydrated and 3 iron, then the reaction should produce 1 2 iron tetroxide and 2 hydrogen (i.e., the calculation of the small amount), and the iron tetroxide is also mixed with unreacted iron elements.

You should read more books, read more and memorize them, and when you receive a certain stage, you will come easily. There are words that you hear hundreds of times and think it's nonsense, and he's the most useful word. Listen to your teachers.

The number of atoms before and after the reaction is unchanged Fe+2H2SO4=FeSO4+H2