Acid oxide

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Acid oxide is a kind of salt and water that can react with alkali oxide 。 Nonmetallic oxide Most are acid oxides, some Transitional element High valence oxides (such as CrO3, Mn2O7, etc.) are also acidic oxides. The acid oxide belongs to acid anhydride, for example, SO2 is called sulfite anhydride, SO3 is called sulfur anhydride, CO2 is called carbonic anhydride, and acetic anhydride is acid anhydride but not acid oxide. The hydrates corresponding to acid oxides are oxyacids, such as H2SO4 for SO3, H2CO3 for CO2, H2SiO3 for SiO2, etc. Most acid oxides can directly combine with water to form oxyacid, while a few acid oxides (SiO2) cannot directly react with water. Acid oxides are generally produced by direct oxidation of nonmetals or thermal decomposition of oxy acid and oxy acid salts.^[1]

Chinese name: Acid oxide
Foreign name: acid (ic) oxide

Pinyin: suān xìng yǎng huà wù
Constituent elements: two types
General: And Alkaline oxide reaction

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Generally Nonmetallic oxide And some Transition metal elements Of High valence oxide 。 for example Phosphorus pentoxide P two O five [i.e. anhydride of phosphoric acid] Manganous oxide Mn two O seven [That is Permanganate Anhydride] Chromium trioxide CrO3 Acid anhydride 】Etc. CO, NO, etc. are neither acid oxides nor Alkaline oxide , but Unsalted oxide Water is a special oxide.

As we know, alkali reacts with acid to form salt and water, and alkali reacts with some non metallic oxide Reactions, as well as carbonates reacting with acids, also produce salts and water . For example

2NaOH+CO two =Na two CO three +H two O

Ca(OH) two +SO three =CaSO four +H two O

Ca(OH) two +SO two =CaSO three ↓+H two O

Such non-metallic oxides are called acid oxides

Most non-metallic oxides are acid oxides. Among the familiar non-metallic oxides, carbon monoxide and nitric oxide They are not acid oxides, because their properties are different from those of acid oxides, and they cannot be classified as acid oxides generally. NO two N two O is also not an acid oxide.

Acid oxides include all oxides with acidity index greater than 1. A typical acid oxide is quartz (SiO two ）Its acidity index is 2, and its solubility in alkaline flux LiM with acidity index of 1 is higher than that in a large number of other oxides, while its solubility in acid flux is lower. Rich in Al two O three 、P two O five And SO three The oxides of are similar. The characteristics of acid oxides are Solubility curve The slope of is positive. Similar to the case of alkaline oxides, the flux with higher lithium oxide content than LiM has better compatibility with these acidic oxides, but it has better fluidity and is easier to crystallize.

Except for the above four oxides, all acid oxides have general solubility, such as TiO two 、WO three And Sb two O three Etc. Its solubility gradually rises to near the middle of LiT-LiM, and then begins to decline, at 80% Lithium tetraborate Near 0 when near. However, this decrease in solubility is accidental, just because of the influence of crystallization, the solubility should be consistent with that of SiO two The same goes on.^[2]

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General

1. Most of them can react with water to generate corresponding acid (except silicon dioxide SiO two And other oxides that cannot react with water)

2. React with alkali to generate only one salt and water

3.& Alkaline oxide reaction

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1. Most acid oxides can directly combine with water to form oxyacids

CO two +H two O=(reversible) H two CO three

SO three +H two O=H two SO four

SO two +H two O=(reversible) H two SO three (Sulfurous acid)

2. Oxyacid can also be decomposed into acid oxides by heating. For example, heating sulfite can obtain sulfur dioxide And water:

H two SO three =SO two +H two O

Here, sulfur dioxide can be regarded as the product of sulfite dehydration

SiO two ,N two O five , is also an acid oxide, but silicon dioxide Insoluble in water, unable to directly combine with water to form silicic acid

3. The most important basis for determining acid oxides is that the chemical valence of each element remains unchanged before and after the chemical reaction

4. It is composed of two elements, one of which is oxygen^[3]