Writing chemical or ionic equations, writing of chemical ionic equations

Let's put it simply, see what the reaction is.

I won't say much about the ordinary equations, just talk about hydrolysis, electrolysis, and ion equations, which are mainly written around these aspects.

Electrolysis is the process in which acid, alkali, salt and water are transformed from mixtures into ions in the environment of water.

For example, NaCl=Na++Cl- To put it bluntly, the left side of the equal sign is the acid-base salt, and the right side is its corresponding anion and ion.

Hydrolysis is a weak acid and weak alkali or weak acid and strong alkali salt in water, due to the poor electrolysis ability of weak roots, it will form weak acid molecules or weak alkali molecules with hydrogen ions and hydroxide ions electrolyzed in water, so that the number of hydroxide ions in the water has changed, and the pH value has been affected.

For example, the acetic acid hydrolysis reactant is acetate and water, and the product is acetic acid and hydroxide.

Electrolysis and hydrolysis occur anytime and anywhere, including water, which itself is also constantly electrolyzed, but the number of hydrogen ions and hydroxide ions in water is the same, so it is not electrical.

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This is how the chemical equation of ion reaction is written, because ions are free. There is no way to precipitate, or precipitate, so you can only take it apart and write e.g. naoh=na, oh-

Depending on the environment in which the reaction is made, it can also be solved, for example, heating, water vapor will naturally be generated, which can react with reactants, and the rest depends on the situation, reacting in solution, that is to say, water may participate.

An ionic equation, i.e., a formula that represents an ionic reaction with the symbol of the ions that actually participate in the reaction.

Refers to the reaction in which soluble substances are detachable. The ionic equation not only represents a certain reaction between certain substances, but also represents the same type of ionic reaction.

For example, H++OH-=H2O can represent the neutralization of many strong acids and bases.

Whether a variety of ions can coexist in the same solution in large quantities can be summed up as: one color, two sexes, three special, and four reactions. To write an ionic equation, you must first determine whether the reaction is an ionic reaction or not.

For example, the reaction of acetic acid with sodium carbonate is an ionic reaction, and the reaction of acetic acid with ethanol to produce ethyl acetate and water is not an ionic reaction.

The chemical formula of a substance that is easily soluble in water and easily ionized is changed to ion.

To be rewritten as ionic substances: strong electrolytes that are easily soluble in water, including:

1. Strong acids: hydrochloric acid, sulfuric acid, nitric acid, etc.

2. Strong alkali: NaOH, KOH, BA(OH)2, etc.

3. Most salt.

Note: Ca(OH)2 slightly soluble clarified lime water: write ions; Lime milk, suspension: write the chemical formula.

Substances that cannot be rewritten as ions, including:

1. Elemental and oxide.

2. Insoluble substances, weak bases: Mg(OH)2, Al(OH)3Cu(OH)2Fe(OH)3, Fe(OH)2, etc.

Salts: BaSO4, PBSO4, AGCL, AGBR, AGI, CaCO3, BaCO3, etc.

3. Weak electrolytes: weak acid, NH3·H2O, H2O4, gas: H2, O2, CO2, SO2, NH3, etc.

The thermochemical equation does not need to indicate the reaction conditions, because it mainly emphasizes what the heat of reaction of the reaction is, rather than emphasizing the conditions under which the reaction can occur, and the heat of reaction is the same regardless of the conditions under which it occurs (some reactions will have subtle differences in the heat of reaction under different conditions, but usually the difference is not large and can be ignored). However, it is important to indicate the state of each substance, because the heat of reaction varies greatly depending on the state.

When writing the ionic formula, precipitation, gas, and water are all required to be written as chemical formulas, while substances that are easily ionized are required to be written in ionic form.

In addition, weak acid ions cannot exist in strong acidic solutions, and weak alkali cations do not exist in strong alkaline solutions.

A correct ionic equation should conform to objective facts and satisfy both the conservation of mass burndown and the conservation of charge. For example: 2Fe+6H+=2Fe3++3H2 (does not conform to objective facts), Na+H2O=Na++OH-+H2 (mass is not conserved) Ag++Cu=Cu2++AG+ (charge is not conserved); Other common mistakes are whether molecules can be disassembled into ionic forms (elemental, gaseous, weak electrolyte, insoluble strong electrolyte, and non-electrolyte cannot be disassembled into ions).

Fe is oxidized to 2-valent under the condition of a weak oxidant and to 3-valent under the condition of a strong oxidant.

Strong electrolytes should be disassembled, such as strong acids, strong bases, salts (soluble).

Weak electrolytes can not be disassembled, such as gases, precipitates, water, weak acids, weak alkalis, insoluble salts.

You don't need to write conditions for thermochemical reaction equations, but you can't make a mistake if you write them.

Thermochemical reaction equations do not need to be written with conditions. In aqueous solution, common ionic compounds that can be ionized strong enough should be disassembled, complexes, chelates, weak electrolytes, precipitates, and organic groups do not need to be written. The molten state is another matter, and the specific analysis of specific problems also requires a certain amount of chemical accumulation. . .

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There are strong electrolytes that need to be disassembled, but some disassemble them in different ways, such as: NaHSO4 has to be disassembled into NA+ H+ SO42-

NaHCO3 is split into Na+ and HCO3-

h2so4=2h+ +so42-

nahco3=na+ +h + co32-2h+ +so42- +ba2+ +2oh-=baso4↓+2h2o

Manganese dioxide reacts with concentrated hydrochloric acid to produce chlorine gas (not ionic reaction).