When there are multiple trims for equations

In some reactions, when there is too much reactant in one of them, two reactions will occur, the reactant is the same, but the product is different.

For example, if NaOH is added dropwise to AlCl3, NaOH is insufficient at first, so AlCl3+3NaOH = Al(OH)3+3NaCl;

AlCl3 is added dropwise to NaOH to start NaOH excess, so AlCl3+4NaOH = Naalo2+2H2O+3NaCl

I have done a problem before to determine whether he is balanced correctly, in fact, it is balanced according to the number of atoms before and after the equal, but if you use the conservation of electrons to match, you will find that it is wrong.

I'll tell you, one, too much is too much like carbon dioxide reacts with sodium hydroxide. Second, there are small equations in the equation, that is, there are small redox reactions included, because there are multiple sets of trim coefficients for small reactions, so there are also multiple sets of reaction coefficients for large reactions. Most of them, though, are the second possibility.

When the reaction involves the problem of excess and under-dosage of reactants, there are multiple ways to balance.

For example: the reaction of dilute nitric acid and copper element.

3*Cu+8*Hno3(rare)=3*Cu(No3)2+2*NO+4*H2O

Reaction of concentrated nitric acid and copper.

Cu+4*Hno3 (concentrated) = Cu(NO3)2+2*NO2+2*H2OSimilarly, chlorine gas is introduced into the ferric bromide solution, and when the amount of chlorine gas introduced is different, the trim method is also different.

This has happened. For example:

3brf3 5h2o hbro3 9br2 hf o2 can be: 8brf3 14h2o 4hbro3 2br2 24hf o2

The reason why this is the case is due to the many different valence states of an element, and the various valence states transform each other. The gain and loss of electrons in the reaction is complex, and one coefficient represents a reaction mechanism, and one electron gain and loss situation.

It seems that there is no specific statement. It depends.

I haven't heard of it, but I've only heard that reactants that want to react differently with the same reactant.

2cri3+21cl2+52koh=2k2cro4+6kio3+42kcl+26h2o

Trim according to the rise and fall of the valence. Iodine increases hexavalent and chromium increases by 3, so each chromium triiodide loses 21 electrons and therefore has a stoichiometric ratio of 2:21 to chlorine

Conservation of charge gain and loss, valence rise and fall conservation, conservation of elements and conservation of mass can be used for balance.

First with the easy, then with the hard. Doesn't the school teacher talk about it?

You look for one.

I'll show you how.

First identify some simple small molecules such as H2O and O2, and then come one by one, and you will be conscious after more practice.

2naclo3 + 4hcl ==2clo2 + cl2 + 2nacl + 2h2o

Cl2 is half of the volume of ClO2, so the ClO2 coefficient is 2, and the Cl2 coefficient is 1ClO2 is all generated by NaClO3, so the NaClO3 coefficient is 2 According to the conservation of Na element, so the NaCl coefficient is 2

According to the conservation of Cl elements, the HCL coefficient is 4

Finally, according to the conservation of the H element, the H2O coefficient is 2