Amphoteric compounds

Chemistry is always a unity of opposites.

Look at the periodic table.

Some elements (almost all metals exhibiting oxidation states +1 and +2) form main oxides and hydroxides. For example, potassium forms the oxide K 2 O, and the hydroxide KOH. They exhibit basic properties, such as interacting with acids.

K2O + HCl → KCl + H2O

Some elements (most non-metals and metals with oxidation states +5, +6, +7) form acidic oxides and hydroxides. Acid hydroxides are oxygen-containing acids, they are called hydroxides because there is a hydroxyl group in the structure, for example, sulfur forms acid oxide SO 3 and acid hydroxide H 2 SO 4 (sulfuric acid):

Such compounds exhibit acidic properties, for example, they react with bases:

H2SO4 + 2KOH → K2SO4 + 2H2O

And there are elements that form such oxides and hydroxides that exhibit both acidic and basic properties. This phenomenon is called amphoteric . Such oxides and hydroxides will be the focus of our attention in this article. All amphoteric oxides and hydroxides are solids, insoluble in water.

First, how do you determine if an oxide or hydroxide is amphoteric? There is a rule, a little conditional, but you can still use it:

Amphoteric hydroxides and oxides are formed by metals, in oxidation states +3 and +4, for example (Al 2 O 3 , Al(Oh) 3 , Fe 2 O 3 , Fe(Oh) 3)

And four exceptions:metalsZn , Be , Pb , sn form the following oxides and hydroxides:ZnO , Zn ( Oh ) 2 , BeO , Be ( Oh ) 2 , PbO , Pb ( Oh ) 2 , SNO , sn ( Oh ) 2 , in which they exhibit an oxidation state of +2, but despite this, these compounds exhibit amphoteric properties .

The most common amphoteric oxides (and their corresponding hydroxides): ZnO, Zn(OH) 2 , BeO, Be(OH) 2 , PbO, Pb(OH) 2 , SnO, Sn(OH) 2 , Al 2 O 3 , Al (OH) 3 , Fe 2 O 3 , Fe(OH) 3 , Cr 2 O 3 , Cr(OH) 3 .

The properties of amphoteric compounds are not difficult to remember: they interact with acids and alkalis.

• with interaction with acids, everything is simple; in these reactions, amphoteric compounds behave like basic ones:

Al 2 O 3 + 6HCl → 2AlCl 3 + 3H 2 O

ZnO + H 2 SO 4 → ZnSO 4 + H 2 O

BeO + HNO 3 → Be(NO 3 ) 2 + H 2 O

Hydroxides react in the same way:

Fe(OH) 3 + 3HCl → FeCl 3 + 3H 2 O

Pb(OH) 2 + 2HCl → PbCl 2 + 2H 2 O

• With interaction with alkalis it is a little more difficult. In these reactions, amphoteric compounds behave like acids, and the reaction products can be different, it all depends on the conditions.

Either the reaction takes place in solution, or the reactants are taken as solids and fused.

Interaction of basic compounds with amphoteric compounds during fusion.

Let's take zinc hydroxide as an example. As mentioned earlier, amphoteric compounds interacting with basic ones behave like acids. So we write zinc hydroxide Zn (OH) 2 as an acid. The acid has hydrogen in front, let's take it out: H 2 ZnO 2. And the reaction of alkali with hydroxide will proceed as if it were an acid. "Acid residue" ZnO 2 2-divalent:

2K Oh(TV) + H 2 ZnO 2 (solid) (t, fusion) → K 2 ZnO 2 + 2 H 2 O

The resulting substance K 2 ZnO 2 is called potassium metazincate (or simply potassium zincate). This substance is a salt of potassium and the hypothetical "zinc acid" H 2 ZnO 2 (it is not entirely correct to call such compounds salts, but for our own convenience we will forget about it). Only zinc hydroxide is written like this: H 2 ZnO 2 is not good. We write as usual Zn (OH) 2, but we mean (for our own convenience) that this is an "acid":

2KOH (solid) + Zn (OH) 2 (solid) (t, fusion) → K 2 ZnO 2 + 2H 2 O

With hydroxides, in which there are 2 OH groups, everything will be the same as with zinc:

Be (OH) 2 (solid.) + 2NaOH (solid.) (t, fusion) → 2H 2 O + Na 2 BeO 2 (sodium metaberyllate, or beryllate)

Pb (OH) 2 (solid.) + 2NaOH (solid.) (t, fusion) → 2H 2 O + Na 2 PbO 2 (sodium metaplumbate, or plumbate)

With amphoteric hydroxides with three OH groups (Al (OH) 3, Cr (OH) 3, Fe (OH) 3) a little differently.

Let's take aluminum hydroxide as an example: Al (OH) 3, write it in the form of an acid: H 3 AlO 3, but we don’t leave it in this form, but take out the water from there:

H 3 AlO 3 - H 2 O → HAlO 2 + H 2 O.

Here we are working with this “acid” (HAlO 2):

HAlO 2 + KOH → H 2 O + KAlO 2 (potassium metaaluminate, or simply aluminate)

But aluminum hydroxide cannot be written like this HAlO 2, we write it down as usual, but we mean “acid” there:

Al (OH) 3 (solid.) + KOH (solid.) (t, fusion) → 2H 2 O + KAlO 2 (potassium metaaluminate)

The same is true for chromium hydroxide:

Cr(OH) 3 → H 3 CrO 3 → HCrO 2

Cr (OH) 3 (solid.) + KOH (solid.) (t, fusion) → 2H 2 O + KCrO 2 (potassium metachromate,

BUT NOT CHROMATE, chromates are salts of chromic acid).

With hydroxides containing four OH groups, it is exactly the same: we bring hydrogen forward and remove water:

Sn(OH) 4 → H 4 SnO 4 → H 2 SnO 3

Pb(OH) 4 → H 4 PbO 4 → H 2 PbO 3

It should be remembered that lead and tin form two amphoteric hydroxides each: with an oxidation state of +2 (Sn (OH) 2, Pb (OH) 2), and +4 (Sn (OH) 4, Pb (OH) 4).

And these hydroxides will form different "salts":

Oxidation state
Hydroxide formula	Sn(OH)2	Pb (OH) 2	Sn(OH)4	Pb(OH)4
Formula of hydroxide as acid	H2SnO2	H2PbO2	H2SnO3	H2PbO3
Salt (potassium)	K2SnO2	K 2 PbO 2	K2SnO3	K2PbO3
Salt name			metastannat	metablumbAT

The same principles as in the names of ordinary "salts", the element in the highest degree oxidation - the suffix AT, in the intermediate - IT.

Such "salts" (metachromates, metaaluminates, metaberyllates, metazincates, etc.) are obtained not only as a result of the interaction of alkalis and amphoteric hydroxides. These compounds are always formed when a strongly basic "world" and an amphoteric one (by fusion) come into contact. That is, just like amphoteric hydroxides with alkalis, both amphoteric oxides and metal salts forming amphoteric oxides (salts of weak acids) will react. And instead of alkali, you can take a strongly basic oxide, and a salt of a metal that forms an alkali (salt of a weak acid).

Interactions:

Remember, the reactions below take place during fusion.

Amphoteric oxide with strongly basic oxide:

ZnO (solid) + K 2 O (solid) (t, fusion) → K 2 ZnO 2 (potassium metazincate, or simply potassium zincate)

Amphoteric oxide with alkali:

ZnO (solid) + 2KOH (solid) (t, fusion) → K 2 ZnO 2 + H 2 O

Amphoteric oxide with a salt of a weak acid and an alkali-forming metal:

ZnO (solid) + K 2 CO 3 (solid) (t, fusion) → K 2 ZnO 2 + CO 2

Amphoteric hydroxide with strongly basic oxide:

Zn (OH) 2 (solid) + K 2 O (solid) (t, fusion) → K 2 ZnO 2 + H 2 O

Amphoteric hydroxide with alkali:

Zn (OH) 2 (solid) + 2KOH (solid) (t, fusion) → K 2 ZnO 2 + 2H 2 O

Amphoteric hydroxide with a salt of a weak acid and an alkali-forming metal:

Zn (OH) 2 (solid) + K 2 CO 3 (solid) (t, fusion) → K 2 ZnO 2 + CO 2 + H 2 O

Salts of a weak acid and a metal that forms an amphoteric compound with a strongly basic oxide:

ZnCO 3 (solid) + K 2 O (solid) (t, fusion) → K 2 ZnO 2 + CO 2

Salts of a weak acid and a metal that forms an amphoteric compound with an alkali:

ZnCO 3 (solid) + 2KOH (solid) (t, fusion) → K 2 ZnO 2 + CO 2 + H 2 O

Salts of a weak acid and a metal that forms an amphoteric compound with a salt of a weak acid and a metal that forms an alkali:

ZnCO 3 (solid) + K 2 CO 3 (solid) (t, fusion) → K 2 ZnO 2 + 2CO 2

Below is information on salts of amphoteric hydroxides, the most common in the exam are marked in red.

	Hydroxide	Acid hydroxide	acid residue		Salt name
BeO	Be(OH) 2	H 2 BeO 2	BeO 2 2-	K 2 BeO 2	Metaberyllate (beryllate)
ZnO	Zn(OH) 2	H 2 ZnO 2	ZnO 2 2-	K 2 ZnO 2	Metazincate (zincate)
Al 2 O 3	Al(OH) 3	HAlO 2	AlO 2 —	KALO 2	Metaaluminate (aluminate)
Fe2O3	Fe(OH)3	HFeO 2	FeO 2 -	KFeO 2	Metaferrate (BUT NOT FERRATE)
	Sn(OH)2	H2SnO2	SnO 2 2-	K2SnO2
	Pb(OH)2	H2PbO2	PbO 2 2-	K 2 PbO 2
SnO 2	Sn(OH)4	H2SnO3	SnO 3 2-	K2SnO3	MetastannAT (stannate)
PbO2	Pb(OH)4	H2PbO3	PbO 3 2-	K2PbO3	MetablumbAT (plumbat)
Cr2O3	Cr(OH)3	HCrO 2	CrO2 -	KCrO 2	Metachromat (BUT NOT CHROMATE)

Interaction of amphoteric compounds with alkali solutions (here only alkalis).

In the Unified State Examination, this is called "the dissolution of aluminum hydroxide (zinc, beryllium, etc.) alkali." This is due to the ability of metals in the composition of amphoteric hydroxides in the presence of an excess of hydroxide ions (in an alkaline medium) to attach these ions to themselves. A particle is formed with a metal (aluminum, beryllium, etc.) in the center, which is surrounded by hydroxide ions. This particle becomes negatively charged (anion) due to hydroxide ions, and this ion will be called hydroxoaluminate, hydroxozincate, hydroxoberyllate, etc. Moreover, the process can proceed in different ways, the metal can be surrounded different number hydroxide ions.

We will consider two cases: when the metal is surrounded four hydroxide ions, and when it is surrounded six hydroxide ions.

Let's write down the abbreviated ionic equation these processes:

Al(OH) 3 + OH - → Al(OH) 4 -

The resulting ion is called the tetrahydroxoaluminate ion. The prefix "tetra" is added because there are four hydroxide ions. The tetrahydroxoaluminate ion has a - charge, since aluminum carries a 3+ charge, and four hydroxide ions 4-, in total it turns out -.

Al (OH) 3 + 3OH - → Al (OH) 6 3-

The ion formed in this reaction is called the hexahydroxoaluminate ion. The prefix "hexo-" is added because there are six hydroxide ions.

It is necessary to add a prefix indicating the amount of hydroxide ions. Because if you just write "hydroxoaluminate", it is not clear which ion you mean: Al (OH) 4 - or Al (OH) 6 3-.

When alkali reacts with amphoteric hydroxide, a salt is formed in solution. The cation of which is an alkali cation, and the anion is a complex ion, the formation of which we considered earlier. The anion is in square brackets.

Al (OH) 3 + KOH → K (potassium tetrahydroxoaluminate)

Al (OH) 3 + 3KOH → K 3 (potassium hexahydroxoaluminate)

What exactly (hexa- or tetra-) salt you write as a product does not matter. Even in the USE answers it is written: “... K 3 (the formation of K is acceptable". The main thing is not to forget to make sure that all indices are correctly affixed. Keep track of the charges, and keep in mind that their sum should be equal to zero.

In addition to amphoteric hydroxides, amphoteric oxides react with alkalis. The product will be the same. Only if you write the reaction like this:

Al 2 O 3 + NaOH → Na

Al 2 O 3 + NaOH → Na 3

But these reactions will not equalize. It is necessary to add water to the left side, because interaction occurs in solution, there is enough water there, and everything will equalize:

Al 2 O 3 + 2NaOH + 3H 2 O → 2Na

Al 2 O 3 + 6NaOH + 3H 2 O → 2Na 3

In addition to amphoteric oxides and hydroxides, some especially active metals interact with alkali solutions, which form amphoteric compounds. Namely, it is: aluminum, zinc and beryllium. To equalize, the left also needs water. And, in addition, the main difference between these processes is the release of hydrogen:

2Al + 2NaOH + 6H 2 O → 2Na + 3H 2

2Al + 6NaOH + 6H 2 O → 2Na 3 + 3H 2

The table below shows the most common USE examples properties of amphoteric compounds:

Amphoteric substance		Salt name
Al2O3 Al(OH)3		Sodium tetrahydroxoaluminate	Al(OH) 3 + NaOH → Na Al 2 O 3 + 2NaOH + 3H 2 O → 2Na 2Al + 2NaOH + 6H 2 O → 2Na + 3H 2
	Na 3	Sodium hexahydroxoaluminate	Al(OH) 3 + 3NaOH → Na 3 Al 2 O 3 + 6NaOH + 3H 2 O → 2Na 3 2Al + 6NaOH + 6H 2 O → 2Na 3 + 3H 2
Zn(OH) 2	K2	Sodium tetrahydroxozincate	Zn(OH) 2 + 2NaOH → Na 2 ZnO + 2NaOH + H 2 O → Na 2 Zn + 2NaOH + 2H 2 O → Na 2 + H 2
	K4	Sodium hexahydroxozincate	Zn(OH) 2 + 4NaOH → Na 4 ZnO + 4NaOH + H 2 O → Na 4 Zn + 4NaOH + 2H 2 O → Na 4 + H 2
Be(OH)2	Li 2	Lithium tetrahydroxoberyllate	Be(OH) 2 + 2LiOH → Li 2 BeO + 2LiOH + H 2 O → Li 2 Be + 2LiOH + 2H 2 O → Li 2 + H 2
	Li 4	Lithium hexahydroxoberyllate	Be(OH) 2 + 4LiOH → Li 4 BeO + 4LiOH + H 2 O → Li 4 Be + 4LiOH + 2H 2 O → Li 4 + H 2
Cr2O3 Cr(OH)3		Sodium tetrahydroxochromate	Cr(OH) 3 + NaOH → Na Cr 2 O 3 + 2NaOH + 3H 2 O → 2Na
	Na 3	Sodium hexahydroxochromate	Cr(OH) 3 + 3NaOH → Na 3 Cr 2 O 3 + 6NaOH + 3H 2 O → 2Na 3
Fe2O3 Fe(OH)3		Sodium tetrahydroxoferrate	Fe(OH) 3 + NaOH → Na Fe 2 O 3 + 2NaOH + 3H 2 O → 2Na
	Na 3	Sodium hexahydroxoferrate	Fe(OH) 3 + 3NaOH → Na 3 Fe 2 O 3 + 6NaOH + 3H 2 O → 2Na 3

The salts obtained in these interactions react with acids, forming two other salts (salts of a given acid and two metals):

2Na 3 + 6H 2 SO 4 → 3Na 2 SO 4 + Al 2 (SO 4 ) 3 + 12H 2 O

That's all! Nothing complicated. The main thing is not to confuse, remember what is formed during fusion, what is in solution. Very often, tasks on this issue come across in B parts.

Zinc is an element of a secondary subgroup of the second group, the fourth period periodic system chemical elements D. I. Mendeleev, with atomic number 30. Denoted by the symbol Zn (lat. Zincum). A simple substance zinc under normal conditions is a brittle transition metal of a bluish-white color (it tarnishes in air, becoming covered with a thin layer of zinc oxide).

In the fourth period, zinc is the last d-element, its valence electrons 3d 10 4s 2 . In education chemical bonds only the electrons of the outer energy level, because the configuration d 10 is very stable. In compounds, zinc has an oxidation state of +2.

Zinc is a reactive metal, has pronounced reducing properties, is inferior in activity to alkaline earth metals. Shows amphoteric properties.

Interaction of zinc with non-metals
When strongly heated in air, it burns with a bright bluish flame to form zinc oxide:
2Zn + O2 → 2ZnO.

When ignited, it reacts vigorously with sulfur:
Zn + S → ZnS.

It reacts with halogens under normal conditions in the presence of water vapor as a catalyst:
Zn + Cl 2 → ZnCl 2 .

Under the action of phosphorus vapor on zinc, phosphides are formed:
Zn + 2P → ZnP 2 or 3Zn + 2P → Zn 3 P 2 .

Zinc does not interact with hydrogen, nitrogen, boron, silicon, carbon.

Interaction of zinc with water
Reacts with water vapor at red heat to form zinc oxide and hydrogen:
Zn + H 2 O → ZnO + H 2.

The interaction of zinc with acids
In the electrochemical series of voltages of metals, zinc is before hydrogen and displaces it from non-oxidizing acids:
Zn + 2HCl → ZnCl 2 + H 2;
Zn + H 2 SO 4 → ZnSO 4 + H 2.

Reacts with dilute nitric acid to form zinc nitrate and ammonium nitrate:
4Zn + 10HNO 3 → 4Zn(NO 3) 2 + NH 4 NO 3 + 3H 2 O.

Reacts with concentrated sulfuric and nitric acid with the formation of a zinc salt and acid reduction products:
Zn + 2H 2 SO 4 → ZnSO 4 + SO 2 + 2H 2 O;
Zn + 4HNO 3 → Zn(NO 3) 2 + 2NO 2 + 2H 2 O

Interaction of zinc with alkalis
Reacts with alkali solutions to form hydroxo complexes:
Zn + 2NaOH + 2H 2 O → Na 2 + H 2

when fused, it forms zincates:
Zn + 2KOH → K 2 ZnO 2 + H 2 .

Interaction with ammonia
With gaseous ammonia at 550–600°C it forms zinc nitride:
3Zn + 2NH 3 → Zn 3 N 2 + 3H 2;
dissolves in an aqueous solution of ammonia, forming tetraamminzinc hydroxide:
Zn + 4NH 3 + 2H 2 O → (OH) 2 + H 2.

Interaction of zinc with oxides and salts
Zinc displaces metals in the stress row to the right of it from solutions of salts and oxides:
Zn + CuSO 4 → Cu + ZnSO 4;
Zn + CuO → Cu + ZnO.

Zinc(II) oxide ZnO - white crystals, when heated, acquire a yellow color. Density 5.7 g/cm 3 , sublimation temperature 1800°C. At temperatures above 1000 ° C, it is reduced to metallic zinc with carbon, carbon monoxide and hydrogen:
ZnO + C → Zn + CO;
ZnO + CO → Zn + CO 2 ;
ZnO + H 2 → Zn + H 2 O.

Does not interact with water. Shows amphoteric properties, reacts with solutions of acids and alkalis:
ZnO + 2HCl → ZnCl 2 + H 2 O;
ZnO + 2NaOH + H 2 O → Na 2.

When fused with metal oxides, it forms zincates:
ZnO + CoO → CoZnO 2 .

When interacting with non-metal oxides, it forms salts, where it is a cation:
2ZnO + SiO 2 → Zn 2 SiO 4,
ZnO + B 2 O 3 → Zn(BO 2) 2.

Zinc (II) hydroxide Zn(OH) 2 - a colorless crystalline or amorphous substance. Density 3.05 g / cm 3, at temperatures above 125 ° C decomposes:
Zn(OH) 2 → ZnO + H 2 O.

Zinc hydroxide exhibits amphoteric properties, easily soluble in acids and alkalis:
Zn(OH) 2 + H 2 SO 4 → ZnSO 4 + 2H 2 O;
Zn(OH) 2 + 2NaOH → Na 2;

also readily soluble in aqueous ammonia to form tetraamminzinc hydroxide:
Zn(OH) 2 + 4NH 3 → (OH) 2.

It is obtained in the form of a white precipitate when zinc salts react with alkalis:
ZnCl 2 + 2NaOH → Zn(OH) 2 + 2NaCl.

Amphoteric oxides (having dual properties) are in most cases metal oxides that have a small electronegativity. Depending on external conditions, they exhibit either acidic or oxide properties. These oxides are formed which usually exhibit the following oxidation states: ll, lll, lV.

Examples of amphoteric oxides: zinc oxide (ZnO), chromium oxide lll (Cr2O3), aluminum oxide (Al2O3), tin oxide ll (SnO), tin oxide lV (SnO2), lead oxide ll (PbO), lead oxide lV (PbO2) , titanium oxide lV (TiO2), manganese oxide lV (MnO2), iron oxide lll (Fe2O3), beryllium oxide (BeO).

Reactions characteristic of amphoteric oxides:

1. These oxides can react with strong acids. In this case, salts of the same acids are formed. Reactions of this type are a manifestation of the properties of the main type. For example: ZnO (zinc oxide) + H2SO4 (hydrochloric acid) → ZnSO4 + H2O (water).

2. When interacting with strong alkalis, amphoteric oxides and hydroxides exhibit. At the same time, the duality of properties (that is, amphotericity) manifests itself in the formation of two salts.

In the melt, when reacting with alkali, an average salt is formed, for example:
ZnO (zinc oxide) + 2NaOH (sodium hydroxide) → Na2ZnO2 (common average salt) + H2O (water).
Al2O3 (aluminum oxide) + 2NaOH (sodium hydroxide) = 2NaAlO2 + H2O (water).
2Al(OH)3 (aluminum hydroxide) + 3SO3 (sulfur oxide) = Al2(SO4)3 (aluminum sulfate) + 3H2O (water).

In solution, amphoteric oxides react with alkali to form a complex salt, for example: Al2O3 (aluminum oxide) + 2NaOH (sodium hydroxide) + 3H2O (water) + 2Na (Al (OH) 4) (sodium tetrahydroxoaluminate complex salt).

3. Each metal of any amphoteric oxide has its own coordination number. For example: for zinc (Zn) - 4, for aluminum (Al) - 4 or 6, for chromium (Cr) - 4 (rarely) or 6.

4. Amphoteric oxide does not react with water and does not dissolve in it.

What reactions prove the amphoteric nature of a metal?

Relatively speaking, an amphoteric element can exhibit the properties of both metals and non-metals. Similar salient feature present in elements of A-groups: Be (beryllium), Ga (gallium), Ge (germanium), Sn (tin), Pb, Sb (antimony), Bi (bismuth) and some others, as well as many elements of B-groups - these are Cr (chromium), Mn (manganese), Fe (iron), Zn (zinc), Cd (cadmium) and others.

Let's prove the following chemical reactions amphotericity of the chemical element zinc (Zn):

1. Zn(OH)2 + N2O5 (dianitrogen pentoxide) = Zn(NO3)2 (zinc nitrate) + H2O (water).
ZnO (zinc oxide) + 2HNO3 = Zn(NO3)2 (zinc nitrate) + H2O (water).

b) Zn(OH)2 (zinc hydroxide) + Na2O (sodium oxide) = Na2ZnO2 (sodium dioxozincate) + H2O (water).
ZnO (zinc oxide) + 2NaOH (sodium hydroxide) = Na2ZnO2 (sodium dioxozincate) + H2O (water).

In the event that an element with dual properties in the compound has the following oxidation states, its dual (amphoteric) properties are most noticeable in the intermediate stage of oxidation.

An example is chromium (Cr). This element has the following oxidation states: 3+, 2+, 6+. In the case of +3, basic and acidic properties are expressed approximately to the same extent, while in Cr +2, basic properties predominate, and in Cr +6, acidic ones. Here are the reactions that prove this statement:

Cr+2 → CrO (chromium oxide +2), Cr(OH)2 → CrSO4;
Cr + 3 → Cr2O3 (chromium oxide +3), Cr (OH) 3 (chromium hydroxide) → KCrO2 or chromium sulfate Cr2 (SO4) 3;
Cr+6 → CrO3 (chromium oxide +6), H2CrO4 → K2CrO4.

In most cases, amphoteric oxides of chemical elements with an oxidation state of +3 exist in the meta form. As an example, one can cite: aluminum metahydroxide (chemical formula AlO (OH) and iron metahydroxide (chemical formula FeO (OH)).

How are amphoteric oxides obtained?

1. The most convenient method of obtaining them is to precipitate from an aqueous solution using ammonia hydrate, that is, a weak base. For example:
Al (NO3) 3 (aluminum nitrate) + 3 (H2OxNH3) (aqueous hydrate) \u003d Al (OH) 3 (amphoteric oxide) + 3NH4NO3 (the reaction is performed at twenty degrees of heat).
Al(NO3)3 (aluminum nitrate) + 3(H2OxNH3) (ammonia hydrate aqueous solution) = AlO(OH) (amphoteric oxide) + 3NH4NO3 + H2O (reaction carried out at 80 °C)

In this case, in an exchange reaction of this type, in the case of an excess of alkalis, it will not precipitate. This is due to the fact that aluminum becomes an anion due to its dual properties: Al (OH) 3 (aluminum hydroxide) + OH- (excess alkali) = - (aluminum hydroxide anion).

Examples of reactions of this type:
Al (NO3) 3 (aluminum nitrate) + 4NaOH (excess sodium hydroxide) = 3NaNO3 + Na (Al (OH) 4).
ZnSO4 (zinc sulfate) + 4NaOH (excess sodium hydroxide) = Na2SO4 + Na2 (Zn (OH) 4).

The salts that are formed in this case belong to They include the following complex anions: (Al (OH) 4) - and also (Zn (OH) 4) 2 -. This is how these salts are called: Na (Al (OH) 4) - sodium tetrahydroxoaluminate, Na2 (Zn (OH) 4) - sodium tetrahydroxozincate. The products of the interaction of aluminum or zinc oxides with solid alkali are called differently: NaAlO2 - sodium dioxoaluminate and Na2ZnO2 - sodium dioxozincate.