Writing of ionic equations related to the amount of reactants

1. For the reaction of acid and base, if the acid is a polyacid (such as CO2 and Ca(OH)2 as you said), it is necessary to pay attention to whether there will be acid salts when the acid is excessive

A small amount of CO2: CO2 + Ca2+ +2OH- = CaCO3 + H2O (to generate positive salts).

Excess CO2: CO2 + OH- = HCO3- (acid salts are generated).

2. For the reaction of salt and acid (base) (such as Naalo2 and HCl), it is necessary to pay attention to whether there is any further reaction with the reactants in the new acid and new salt generated

HCl in small amounts: AlO2- +H+ +H2O = Al(OH)3

HCl excess: Al(Oh)3 + 3H+ = Al3+ + 3H2O (the new acid Al(Oh)3 can react further with the reactant HCl).

This general occurrence occurs in amphoteric compounds such as the AL series.

3. For some redox reactions, it is also necessary to pay attention to whether the oxidation products (reduction products) can continue to react with the reducing agent or oxidant

Cl2 minority: 2p + 3Cl2 = 2pCl3

Cl2 excess: 2p + 5Cl2 = 2Pcl5 (can be seen as Pcl3 continuing to react with Cl2).

Fe small amount: Fe + 4H+ + No3- = Fe3+ + No + 2H2O

Excess Fe: 3Fe + 8H+ +2NO3- = 3Fe2+ +2O + 4H2O (the Fe3+ formed by Fe3+ is reduced by Fe).

4. I can't remember ...... for the time being

Because the amount of reactants is different, the substances formed may also be different. For example, carbon dioxide reacts with calcium hydroxide to form calcium carbonate and water, and if carbon dioxide is introduced again, then carbon dioxide will react with calcium carbonate to form calcium bicarbonate. Whether it is different depends on whether it can be advanced and not react.

Writing of ionic reaction equations for quantities (only partial):

Example 1: Inject NaOH solution into the AlCl3 solution to an excessive amount, and the ion reaction is written step by step

al3++3oh-==al(oh)3↓

Al(OH)3+OH-==ALO2-+2H2OIf ALCL3 solution is dropped into the NaOH solution to an excess, the ionic reaction is written step by step:

al3++4oh-==alo2-+2h2o3alo2-+al3++6h2o==4al(oh)3↓<>

If an excess of NaOH solution is added to the AlCl3 solution, the ionic reaction is completed in one step

If a small amount of NaOH solution is added to the sufficient amount of Al2(SO4)3 solution, the ion equation is:

al3++3oh-==al(oh)3↓

Example 2: Hydrochloric acid solution is dropped into the Naalo2 solution to an excessive amount, and the ionic reaction is written step by step

alo2-+h++h2o==al(oh)3↓al(oh)3+3h+==al3++3h2o<>

If the Naalo2 solution is dropped into the hydrochloric acid solution to an excess, the ionic reaction is written step by step

alo2-+4h+==al3++2h2o

3alo2-+Al3++6H2O==4Al(OH)3 If an excess hydrochloric acid solution is added to the Naalo2 solution, the ionic reaction is completed in one step

alo2-+4h+==al3++2h2o

If a small amount of Shenjian hydrochloric acid solution is added to a sufficient amount of Naalo2 solution, the ion equation is:

alo2-+h++h2o==al(oh)3↓

ionsEquationsoh⁻＋h⁺＝h₂o。

The process of writing the ion equation:

1. Write the equation first: BA(OH) +2HCl=BACL +2HO.

2. Then disassemble: BA +2OH +2H +2Cl =BA +2Cl +2HO.

3. Remove the same ions on both sides: 2oh +2h = 2h o.

4. Divide both sides by 2 at the same time: oh + h = h o.

Error-prone analysis. All oxides and peroxides.

Always write the chemical formula, which must be clear here, like sodium peroxide.

Reactive metal oxides or peroxides, such as sodium oxide, are soluble electrolytes but cannot be separated.

There are also things like sodium bicarbonate.

It is a strong electrolyte that is soluble, but sometimes (e.g., saturated sodium carbonate.

Zhongtong carbon dioxide) is also written as a chemical formula, so it depends on whether it exists mainly in the form of a solid substance or in the form of ions in solution.

Acidic salts with strong acids.

For example, sodium bisulfate should be divided into sodium ions, hydrogen ions and sulfate ions (only bisulfate belongs to this category in high schools); Weakly acidic salts, such as sodium bicarbonate, are split into sodium ions and bicarbonate.

Ions (acid salts such as carbonic acid, phosphoric acid, sulfurous acid, etc.)

Weak electrolytes, non-electrolytes, oxides, elemental matter, precipitation, and gases cannot be disassembled.

The ionic reaction equation is an equation that describes the reaction process between ions when ionic compounds are reacted in an aqueous solution. It is a type of chemical state open-mode reaction equation that describes the interactions and transformations between ions in chemical reactions. The following describes how to write the ionic reaction equation in detail.

The writing of the ionic reaction equation is usually divided into the following steps:

Determination of reactants and products: First of all, it is necessary to determine the type and quantity of reactants and products, which needs to be determined by methods such as chemical experiments and chemical calculations.

Write the ionic formula of reactants and products: The ionic reaction equation needs to be written first. The ionic formula refers to the chemical formula of the ions in a compound, which is made up of cations and anions.

In the ionic formula, positive ions are usually written in front and negative ions are written in the back, and the two are connected with a "+".

Determine the reaction process according to the type of reaction: Determine the reaction process according to the type of reaction, and the common types of reactions include acid-base reaction, redox reaction, complexation reaction, etc. Different methods are required to write the ionic reaction equation for different reaction types.

Maintain charge balance: The ionic reaction equation requires maintaining charge equilibrium, i.e., the total charge of the reactants is equal to the total charge of the product. When writing the ionic reaction equation, the reaction formula needs to be balanced according to the charge of the ion.

Check the correctness of the equation: After writing the ionic reaction equation, you need to check the correctness of the equation. The inspection method includes checking the charge balance of ions, whether the types and quantities of reactants and products are consistent, etc.

The following takes acid-base reaction as an example to illustrate how to write the ionic reaction equation.

Acid-base reaction refers to the reaction of an acid and a base in an aqueous solution. For example, the reaction of sulfuric acid and sodium hydroxide can be written as follows:

h2so4 + 2naoh → na2so4 + 2h2o

In this equation, H2SO4 and NaOH represent sulfuric acid and sodium hydroxide, respectively, and their ionic formulas are H+, SO42- and Na+, Oh-, respectively. The process of the reaction is that the hydrogen ions in the acid and the hydroxide ions in the base combine to form water molecules and release salts.

When writing this equation, it is necessary to maintain the charge equilibrium, i.e., the total charge of the reaction prestate and the product is equal. In this equation, the total charge of both the reactant and the product is zero, so it satisfies the requirement of charge balance.

In the actual writing of the ionic reaction equation, it needs to be adjusted and modified according to the specific reaction type and the type and quantity of reactants. At the same time, after writing the ionic reaction equation, the equation needs to be checked to ensure its correctness and completeness.

Ca(OH)2+2NaHCO3 (excess) ==CaCO3 +H2O+Na2CO3Ca(OH)2 (excess) + NaHCO3==CaCO3 +H2O+NaOH Excess and small amounts are relative, and are considered excessive when a substance is left over (which does not produce any chemical reaction when this substance is added) If there is an excess of NaHCO3, then the product does not contain any anions and cations (CA ions, OH root) is a formula, because there is also an OH root that can react with HCO3 root in the second formula. If there is an excess of Ca(OH)2, then there can be no CO3 root as in the equation because it can react with Ca ions. There is one more way:

The two reactants can react chemically with Ca ions and CO3, OH and HCO3, if one side is excessive, it will definitely neutralize all the reactive anions and cations (Ca ions, OH roots or HCO3) on the other side, so a formula requires 2mol of NaHCO3 to completely react 1mol of Ca(OH)2 because Ca(OH)2 has two OH roots (2 HCO3 are needed), and 1 Ca (one CO3 is needed, is generated by OH root and HCO3) so the coefficient is 2