How to balance chemical equations, students give examples

There are many chemical trim methods, I don't know which one you are talking about, so I have said all four of these methods, Feng Tan hopes it will help you! Hehe!

a) Least common multiple method.

This method is suitable for common chemical equations that are not too difficult. 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:

2kclo2kcl3o2

2) Odd-even equalization.

This method is suitable for multiple occurrences of an element on both sides of a chemical equation where 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 with the oxygen atom with the highest number of occurrences. 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 written: 2C

h5o=4co2h

o iii) Observation balancing.

Sometimes there will be a substance with a 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, Fe in 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 thus the H2 coefficient is 4, write the silver to know the condition, ** Change to an equal sign:

3fe+4h

o==feo4h Note] In the chemical equation of this entry, the ones that are not in bold are the foot marks.

In this experiment, H2O must be gaseous, so H2 is not superscripted.

4) Normalization Law.

Find the key chemical formula in the chemical equation, set the number before the chemical formula as 1, and then balance the number before the other chemical formulas 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.

Method: Select the most complex chemical formula in the chemical equation, let its coefficient be 1, and then infer it in turn.

Step 1: Let the factor of NH3 be 1

1nh3+o2——no+h2o

Step 2: The N and H atoms in the reaction are transferred to No and H2O respectively, by.

Step 3: Push the O2 coefficient from the total number of oxygen atoms at the right end.

The acid-base reaction balances the hydroxide and the number of hydrogen ions, for example.

An ideal example [H]Cl+ Na[OH]=NaCl+H2OAnother example [H2]SO4+K[OH]->K2SO4+H2O2H We need 2 OH to neutralize.

So [H2]SO4+2K[OH]=K2SO4+2H2O complex point.

H3ClO4 + Mg(OH)2->MgCl2 + H2O3Hydrogen 2Oxygen.

Let's take the least common multiple of 6

3x2 h 2x3oh

2H3ClO4+3mg(OH)2=3mgCl2+6H2O redox reaction.

It is about balancing the gains and losses of chemical valence.

no2+h2o->hno3+no

n Autoredox: +4->+5 +1 to nitric acid + 4-> +2 -2 to NO

So to trim, you need to make the n of the price increase twice as much as the n of the price reduction.

3NO2+H2O = [2]HNO3+[1]NO2Fe+H2O+O2->Fe(OH)3

fe:0->+3

o2 :2*0->2*-2=-4

So the Fe,O2 ratio is 4:3

4Fe + 3O2 + H2O-> 4Fe(OH)34Fe + 3O2 + [6]H2O=4Fe(Oh)3 organic bond breaking reaction.

H2 and alkenes. h h

c=c/ \

H H A double bond requires one H-H (hydrogen) to break.

This type of molecule, CNH2N, contains 1 double bond.

cnh2n+h2=c2h(2n+2)

If it is a double double bonded ene.

e.g. C4H6: the general term CNH2N-2

h2c=ch-ch=ch2

We need two hydrogen gases to complete the complete reaction.

cnh2n-2+2h2=cnh2n+2

It should be enough for you for the time being, but if you talk too much, you will be dizzy.

Chemical reactions strictly follow the law of conservation of mass, and after the equation is written out of reactants and products, the number of left and right of each molecule is often different, which requires balancing to solve. Reference.

Least common multiple method.

This method is suitable for common chemical equations that are not too difficult. 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, so the least common multiple is 6, so the coefficient before kclo3 should be 2, and O2 should be preceded by 3, and the formula becomes: 2kclo3 kcl+3O2, because the number of potassium atoms and chlorine atoms on the left becomes 2, then the coefficient of 2 before KCL, ** is changed to equal sign.