Potassium, sodium or lithium may react with water. In this case, compounds related to hydroxides are found in the reaction products. The properties of these substances, the peculiarities of the occurrence of chemical processes in which bases participate, are determined by the presence of a hydroxyl group in their molecules. Thus, in electrolytic dissociation reactions, bases are split into metal ions and OH - anions. We will look at how bases interact with non-metal oxides, acids and salts in our article.
Nomenclature and structure of the molecule
To correctly name the base, you need to add the word hydroxide to the name of the metal element. Let's give specific examples. Aluminum base belongs to amphoteric hydroxides, the properties of which we will consider in the article. The obligatory presence in the molecules of bases of a hydroxyl group associated with the metal cation by an ionic type of bond can be determined using indicators, for example, phenolphthalein. In an aqueous environment, an excess of OH - ions is determined by the change in color of the indicator solution: colorless phenolphthalein becomes crimson. If a metal exhibits multiple valencies, it can form multiple bases. For example, iron has two bases, in which it is equal to 2 or 3. The first compound is characterized by the characteristics of the second - amphoteric. Therefore, the properties of higher hydroxides differ from compounds in which the metal has a lower degree of valence.
Physical characteristics
Bases are solid substances that are resistant to heat. In relation to water, they are divided into soluble (alkalis) and insoluble. The first group is formed by chemically active metals - elements of the first and second groups. Substances that are insoluble in water consist of atoms of other metals whose activity is inferior to sodium, potassium or calcium. Examples of such compounds are iron or copper bases. The properties of hydroxides will depend on which group of substances they belong to. Thus, alkalis are thermally stable and do not decompose when heated, while bases insoluble in water are destroyed under the influence of high temperature, forming oxide and water. For example, copper base decomposes as follows:
Cu(OH) 2 = CuO + H 2 O
Chemical properties of hydroxides
The interaction between two important groups of compounds - acids and bases - is called in chemistry a neutralization reaction. This name can be explained by the fact that chemically aggressive hydroxides and acids form neutral products - salts and water. Being, in fact, an exchange process between two complex substances, neutralization is characteristic of both alkalis and water-insoluble bases. Let us give the equation for the neutralization reaction between caustic potassium and chloride acid:
KOH + HCl = KCl + H2O
An important property of alkali metal bases is their ability to react with acidic oxides, resulting in salt and water. For example, by passing carbon dioxide through sodium hydroxide, you can obtain its carbonate and water:
2NaOH + CO 2 = Na 2 CO 3 + H 2 O
Ion exchange reactions include the interaction between alkalis and salts, which occurs with the formation of insoluble hydroxides or salts. Thus, by pouring the solution dropwise into a solution of copper sulfate, you can obtain a blue jelly-like precipitate. This is a copper base, insoluble in water:
CuSO 4 + 2NaOH = Cu(OH) 2 + Na 2 SO 4
The chemical properties of hydroxides, insoluble in water, differ from alkalis in that when slightly heated they lose water - they dehydrate, turning into the form of the corresponding basic oxide.
Bases exhibiting dual properties
If an element or can react with both acids and alkalis, it is called amphoteric. These include, for example, zinc, aluminum and their bases. The properties of amphoteric hydroxides make it possible to write their molecular formulas both in the form of a hydroxo group and in the form of acids. Let us present several equations for the reactions of aluminum base with chloride acid and sodium hydroxide. They illustrate the special properties of hydroxides, which are amphoteric compounds. The second reaction occurs with the decomposition of alkali:
2Al(OH) 3 + 6HCl = 2AlCl 3 + 3H 2 O
Al(OH) 3 + NaOH = NaAlO 2 + 2H 2 O
The products of the processes will be water and salts: aluminum chloride and sodium aluminate. All amphoteric bases are insoluble in water. They are extracted as a result of the interaction of appropriate salts and alkalis.
Methods of preparation and use
In industries requiring large volumes of alkalis, they are obtained by electrolysis of salts containing cations of active metals of the first and second groups of the periodic table. The raw material for the extraction of, for example, sodium hydroxide is a solution of table salt. The reaction equation will be:
2NaCl + 2H 2 O = 2NaOH + H 2 + Cl 2
Bases of low-active metals are obtained in the laboratory by reacting alkalis with their salts. The reaction is an ion exchange type and ends with the precipitation of a base. A simple way to produce alkalis is a substitution reaction between the active metal and water. It is accompanied by heating of the reacting mixture and is of the exothermic type.
The properties of hydroxides are used in industry. Alkalies play a special role here. They are used as kerosene and gasoline purifiers, for making soap, processing natural leather, as well as in technologies for the production of artificial silk and paper.
basic hydroxides Wikipedia, basic hydroxides groupBasic hydroxides- these are complex substances that consist of metal atoms or ammonium ions and hydroxo groups (-OH) and dissociate in an aqueous solution to form OH− anions and cations. The name of the base usually consists of two words: the word "hydroxide" and the name of the metal in the genitive case (or the word "ammonium"). Bases that are highly soluble in water are called alkalis.
- 1 Receipt
- 2 Classification
- 3 Nomenclature
- 4 Chemical properties
- 5 See also
- 6 Literature
Receipt
Sodium hydroxide granules Calcium hydroxide Aluminum hydroxide Iron metahydroxide- The interaction of a strong base oxide with water produces a strong base or alkali. Weakly basic and amphoteric oxides do not react with water, so the corresponding hydroxides cannot be obtained in this way.
- Hydroxides of low-active metals are obtained by adding alkali to solutions of the corresponding salts. Since the solubility of weakly basic hydroxides in water is very low, the hydroxide precipitates from solution in the form of a gelatinous mass.
- The base can also be obtained by reacting an alkali or alkaline earth metal with water.
- Alkali metal hydroxides are produced industrially by electrolysis of aqueous salt solutions:
- Some bases can be obtained by exchange reactions:
- Metal bases are found in nature in the form of minerals, for example: hydrargillite Al(OH)3, brucite Mg(OH)2.
Classification
The bases are classified according to a number of characteristics.
- According to solubility in water.
- Soluble bases (alkalis): lithium hydroxide LiOH, sodium hydroxide NaOH, potassium hydroxide KOH, barium hydroxide Ba(OH)2, strontium hydroxide Sr(OH)2, cesium hydroxide CsOH, rubidium hydroxide RbOH.
- Practically insoluble bases: Mg(OH)2, Ca(OH)2, Zn(OH)2, Cu(OH)2, Al(OH)3, Fe(OH)3, Be(OH)2.
- Other bases: NH3 H2O
The division into soluble and insoluble bases almost completely coincides with the division into strong and weak bases, or hydroxides of metals and transition elements. The exception is lithium hydroxide LiOH, which is highly soluble in water but is a weak base.
- By the number of hydroxyl groups in the molecule.
- Monoacid (sodium hydroxide NaOH)
- Diacid (copper(II) hydroxide Cu(OH)2)
- Triacid (iron(III) hydroxide Fe(OH)3)
- By volatility.
- Volatile: NH3, CH3-NH2
- Non-volatile: alkalis, insoluble bases.
- In terms of stability.
- Stable: sodium hydroxide NaOH, barium hydroxide Ba(OH)2
- Unstable: ammonium hydroxide NH3·H2O (ammonia hydrate).
- According to the degree of electrolytic dissociation.
- Strong (α > 30%): alkalis.
- Weak (α< 3 %): нерастворимые основания.
- By the presence of oxygen.
- Oxygen-containing: potassium hydroxide KOH, strontium hydroxide Sr(OH)2
- Oxygen-free: ammonia NH3, amines.
- By connection type:
- Inorganic bases: contain one or more -OH groups.
- Organic bases: organic compounds that are proton acceptors: amines, amidines and other compounds.
Nomenclature
According to IUPAC nomenclature, inorganic compounds containing -OH groups are called hydroxides. Examples of systematic names of hydroxides:
- NaOH - sodium hydroxide
- TlOH - thallium(I) hydroxide
- Fe(OH)2 - iron(II) hydroxide
If a compound contains oxide and hydroxide anions simultaneously, then numerical prefixes are used in the names:
- TiO(OH)2 - titanium dihydroxide-oxide
- MoO(OH)3 - molybdenum trihydroxide-oxide
For compounds containing the O(OH) group, traditional names with the prefix meta- are used:
- AlO(OH) - aluminum metahydroxide
- CrO(OH) - chromium metahydroxide
For oxides hydrated by an indefinite number of water molecules, for example Tl2O3 n H2O, it is unacceptable to write formulas like Tl(OH)3. Such compounds are also called hydroxides not recommended. Examples of names:
- Tl2O3 n H2O - thallium(III) oxide polyhydrate
- MnO2 n H2O - manganese(IV) oxide polyhydrate
Special mention should be made of the compound NH3 H2O, which was previously written as NH4OH and which exhibits the properties of a base in aqueous solutions. This and similar compounds should be referred to as hydrate:
- NH3 H2O - ammonia hydrate
- N2H4 H2O - hydrazine hydrate
Chemical properties
- In aqueous solutions, bases dissociate, which changes the ionic equilibrium:
- litmus turns blue
- methyl orange - yellow,
- phenolphthalein takes on a fuchsia color.
- When interacting with an acid, a neutralization reaction occurs and salt and water are formed:
- If there is an excess of acid or base, the neutralization reaction does not proceed to completion and acidic or basic salts are formed, respectively:
- Amphoteric bases can react with alkalis to form hydroxo complexes:
- Bases react with acidic or amphoteric oxides to form salts:
- Bases enter into exchange reactions (react with salt solutions):
- Weak and insoluble bases decompose when heated into oxide and water:
- Alkali metal bases (except lithium) melt when heated; the melts are electrolytes.
See also
- Acid
- Oxides
- Hydroxides
- Theories of acids and bases
Literature
- Chemical Encyclopedia / Editorial Board: Knunyants I.L. and others. - M.: Soviet Encyclopedia, 1988. - T. 1. - 623 p.
- Chemical Encyclopedia / Editorial Board: Knunyants I.L. and others. - M.: Soviet Encyclopedia, 1992. - T. 3. - 639 p. - ISBN 5-82270-039-8.
- Lidin R.A. and others. Nomenclature of inorganic substances. - M.: KolosS, 2006. - 95 p. - ISBN 5-9532-0446-9.
basic hydroxides, basic hydroxides Wikipedia, basic hydroxides of the group, basic hydroxides are
2NaOH + CO 2 = Na 2 CO 3 + H 2 O,
base acid salt
Cu(OH) 2 + H 2 SO 4 = CuSO 4 + 2H 2 O,
base acid salt
2NaOH + PbO = Na 2 PbO 2 + H 2 O,
base amphoteric salt
2NaOH + Pb(OH) 2 = Na 2 PbO 2 + 2H 2 O,
base amphoteric salt
hydroxide
2H 3 PO 4 + 3Na 2 O = 2Na 3 PO 4 + 3H 2 O,
acid basic salt
H 2 SO 4 + SnO = SnSO 4 + H 2 O,
acid amphoteric salt
H 2 SO 4 + Sn(OH) 2 = SnSO 4 + 2H 2 O.
acid amphoteric salt
hydroxide
Amphoteric hydroxides exhibit the following basic properties in reactions with acids:
2Al(OH) 3 + 3H 2 SO 4 = Al 2 (SO 4) 3 + 6H 2 O,
with alkalis (bases) – acidic properties:
H 3 AlO 3 + 3NaOH = Na 3 AlO 3 + 3H 2 O,
or H 3 AlO 3 + NaOH = NaAlO 2 + 2H 2 O.
Bases and acids react with salts to form a precipitate or weak electrolyte. Weak acids - H 3 PO 4, H 2 CO 3, H 2 SO 3, H 2 SiO 3 and others.
2NaOH + NiSO 4 = Ni(OH) 2 + Na 2 SO 4,
base salt
3H 2 SO 4 + 2Na 3 PO 4 = 2H 3 PO 4 + 3Na 2 SO 4
acid salt
Oxygen-free acids undergo the same reactions as the previously discussed oxygen-containing acids.
Example. Make up the formulas of hydroxides corresponding to the oxides: a) FeO; b) N 2 O 3; c) Cr 2 O 3. Name the connections.
Solution
a) FeO is a basic oxide, therefore, the corresponding hydroxide is a base; in the base formula, the number of hydroxyl groups (OH) is equal to the oxidation state of the metal atom; the formula of iron (II) hydroxide is Fe(OH) 2.
b) N 2 O 3 is an acidic oxide, therefore the corresponding hydroxide is an acid. The acid formula can be obtained based on the representation of the acid as a hydrate of the corresponding oxide:
N2O3. H 2 O = (H 2 N 2 O 4) = 2HNO 2 – nitrous acid.
c) Cr 2 O 3 is an amphoteric oxide, therefore, the corresponding hydroxide is amphoteric. Amphoteric hydroxides are written in the form of bases - Cr(OH) 3 - chromium (III) hydroxide.
Salts
Salts- substances that consist of basic and acidic residues. Thus, the salt CuSO 4 consists of a main residue - the metal cation Cu 2+ and an acid residue - SO 4 2 .
According to traditional nomenclature, the names of salts of oxygen acids are composed as follows: the ending - is added to the root of the Latin name of the central atom of the acidic residue - at(at higher oxidation states of the central atom) or – it(for a lower oxidation state) and then - the remainder of the base in the genitive case, for example: Na 3 PO 4 - sodium phosphate, BaSO 4 - barium sulfate, BaSO 3 - barium sulfite. The names of salts of oxygen-free acids are formed by adding the suffix - to the root of the Latin name of the non-metal. eid and the Russian name of the metal (residue from the base), for example CaS - calcium sulfide.
Medium salts do not contain in its composition, hydrogen ions and hydroxo groups that can be replaced by metal, for example CuCl 2, Na 2 CO 3 and others.
Chemical properties of salts
Medium salts enter into exchange reactions with alkalis, acids, and salts. For examples of appropriate reactions, see above.
Acid salts contain the acid residue contains a hydrogen ion, for example NaHCO 3, CaHPO 4, NaH 2 PO 4, etc. In the name of an acid salt, the hydrogen ion is denoted by the prefix hydro-, before which the number of hydrogen atoms in the salt molecule is indicated if it is greater than one. For example, the names of the salts of the above composition are, respectively, sodium bicarbonate, calcium hydrogen phosphate, sodium dihydrogen phosphate.
Acid salts are obtained
interaction between the base and polybasic acid with excess acid:
Ca(OH) 2 + H 3 PO 4 = CaHPO 4 + 2H 2 O;
the interaction of the average salt of a polybasic acid and the corresponding acid or a stronger acid taken in deficiency:
CaCO 3 + H 2 CO 3 = Ca(HCO 3) 2,
Na 3 PO 4 + HCl = Na 2 HPO 4 + NaCl.
Basic salts contain the base residue contains a hydroxo group, for example CuOHNO 3, Fe(OH) 2 Cl. In the name of the main salt, the hydroxo group is designated by the prefix hydroxo-, for example, the names of the above salts are respectively: copper (II) hydroxonitrate, iron (III) dihydroxychloride.
Basic salts are obtained
the interaction of a polyacid (containing more than one hydroxo group) base and acid with an excess of base:
Cu(OH) 2 + HNO 3 = CuOHNO 3 + H 2 O;
the interaction of a salt formed by a polyacid base and a base taken in deficiency:
FeCl 3 + NaOH = FeOHCl 2 + NaCl,
FeCl 3 + 2NaOH = Fe(OH) 2 Cl + 2NaCl.
Acidic and basic salts have all the properties of salts. In reactions with alkalis, acidic salts, and with acids, basic salts turn into intermediate salts.
Na 2 HPO 4 + NaOH = Na 3 PO 4 + H 2 O,
Na 2 HPO 4 + 2HCl = H 3 PO 4 + 2NaCl,
FeOHCl 2 + HCl = FeCl 3 + H 2 O,
FeOHCl 2 + 2NaOH = Fe(OH) 3 + 2NaCl.
Example 1. Make up the formulas of all salts that can be formed by the base Mg(OH) 2 and the acid H 2 SO 4.
Solution
We compose salt formulas from possible basic and acidic residues, observing the rule of electrical neutrality. Possible basic residues are Mg 2+ and MgOH +, acidic residues are SO 4 2- and HSO 4 . The charges of complex basic and acidic residues are equal to the sum of the oxidation states of their constituent atoms. Using a combination of basic and acidic residues, we compose the formulas of possible salts: MgSO 4 - average salt - magnesium sulfate; Mg(HSO 4) 2 – acid salt – magnesium hydrogen sulfate; (MgOH) 2 SO 4 – the main salt is magnesium hydroxysulfate.
Example 2. Write the reactions of salt formation during the interaction of oxides
a) PbO and N 2 O 5; b) PbO and Na 2 O.
Solution
In reactions between oxides, salts are formed, the basic residues of which are formed from basic oxides, the acid residues from acidic oxides.
a) In the reaction with the acidic oxide N 2 O 5, the amphoteric oxide PbO exhibits the properties of a basic oxide, therefore, the main residue of the resulting salt is Pb 2+ (the charge of the lead cation is equal to the oxidation state of lead in the oxide), the acid residue is NO 3 - (acid residue corresponding to the given acidic nitric oxide). Reaction equation
PbO + N 2 O 5 = Pb(NO 3) 2.
b) In the reaction with the basic oxide Na 2 O, the amphoteric oxide PbO exhibits the properties of an acidic oxide; the acidic residue of the resulting salt (PbO 2 2 ) is found from the acid form of the corresponding amphoteric hydroxide Pb(OH) 2 = H 2 PbO 2. Reaction equation
HYDROXIDES, inorganic metal compounds of the general formula M(OH)n, where M is a metal, n is its oxidation state. Base hydroxides or amphoteric (have acidic and basic properties) compounds, alkali and alkaline earth hydroxides... ... Modern encyclopedia
Chemical compounds of oxides with water. Hydroxides of many metals are bases, and nonmetals are acids. Hydroxides exhibiting both basic and acidic properties are called amphoteric. Typically the term hydroxide refers only to bases. Cm.… … Big Encyclopedic Dictionary
HYDROXIDES, inorganic chemical compounds containing the OH ion, exhibiting the properties of BASES (substances that add protons and react with an acid, thereby forming salt and water). Strong inorganic bases such as... ... Scientific and technical encyclopedic dictionary
HYDROXIDES- chem. connections (see) with water. G. many metals (see), and non-metals (see). In the base formula, the chemical comes first. symbol of a metal, on the second oxygen and on the last hydrogen (potassium hydroxide KOH, sodium hydroxide NaOH, etc.). Group… … Big Polytechnic Encyclopedia
Chemical compounds of oxides with water. Hydroxides of many metals are bases, and nonmetals are acids. Hydroxides exhibiting both basic and acidic properties are called amphoteric. Usually the term "hydroxides" refers only to bases... Encyclopedic Dictionary
Inorg. conn. metals of the general type M(OH)n, where and the oxidation state of the metal is M. They are bases or amphoteric compounds. G. alkaline, alkaline. land metals and Tl(I) called alkalis, crystalline lattices G. alkaline and alkaline. land metals contain... ... Chemical encyclopedia
Inorganic compounds containing one or more OH groups. May be bases or amphoteric compounds (see Amphotericity). G. are found in nature in the form of minerals, for example hydrargillite A1(OH)3, brucite Mg(OH)2 ... Big Encyclopedic Polytechnic Dictionary
Chem. conn. oxides with water. G. pl. metals are bases and nonmetals are acids. G., exhibiting both basic and acidic properties are called. amphoteric. Usually the term G. refers only to the bases. See also Alkalis... Natural science. Encyclopedic Dictionary
hydroxides- hydroxides, ov, units. h. with id, and ... Russian spelling dictionary
hydroxides- pl., R. hydroxy/dov; units hydroxy/d (2 m) ... Spelling dictionary of the Russian language
Books
- Chemistry. Textbook for academic bachelor's degree, O.S. Zaitsev. When opening the course, special attention is paid to the issues of thermodynamics and kinetics of chemical reactions. For the first time, issues of a new area of chemical knowledge, extremely important for specialists, are presented...
- Inorganic and analytical chemistry of scandium, L. N. Komissarova. The monograph summarizes information about the main groups of inorganic scandium compounds (intermetallic compounds, binary oxygen-free compounds, including halides and thiocyanates, complex oxides,...
Hydroxides can be thought of as the product of the addition (real or mental) of water to the corresponding oxides. Hydroxides are divided into bases, acids, and amphoteric hydroxides. Bases have the general composition M(OH)x, acids have the general composition HxCo. In molecules of oxygen-containing acids, the replaced hydrogen atoms are connected to the central element through oxygen atoms. In molecules of oxygen-free acids, hydrogen atoms are attached directly to a non-metal atom. Amphoteric hydroxides include primarily hydroxides of aluminum, beryllium and zinc, as well as hydroxides of many transition metals in intermediate oxidation states.
Based on solubility in water, soluble bases are distinguished - alkalis (formed by alkali and alkaline earth metals). The bases formed by other metals do not dissolve in water. Most inorganic acids are soluble in water. Only silicic acid H2SiO3 is a water-insoluble inorganic acid. Amphoteric hydroxides do not dissolve in water.
Chemical properties of bases.
All bases, both soluble and insoluble, have a common characteristic property - to form salts.
Let's consider the chemical properties of soluble bases (alkalis):
1. When dissolved in water, they dissociate to form a metal cation and a hydroxide anion. Change the color of the indicators: violet litmus - to blue, phenolphthalein - to crimson, methyl orange - to yellow, universal indicator paper - to blue.
2. Interaction with acid oxides:
alkali + acid oxide = salt.
3. Interaction with acids:
alkali + acid = salt + water.
The reaction between an acid and alkali is called a neutralization reaction.
4. Interaction with amphoteric hydroxides:
alkali + amphoteric hydroxide = salt (+ water)
5. Interaction with salts (subject to the solubility of the original salt and the formation of a precipitate or gas as a result of the reaction.
Let's consider the chemical properties of insoluble bases:
1. Interaction with acids:
base + acid = salt + water.
Polyacid bases are capable of forming not only intermediate, but also basic salts.
2. Heat decomposition:
base = metal oxide + water.
Chemical properties of acids.
All acids have a common characteristic property - the formation of salts when replacing hydrogen cations with metal/ammonium cations.
Let's consider the chemical properties of water-soluble acids:
1. When dissolved in water, they dissociate to form hydrogen cations and an acid residue anion. Change the color of the indicators to red (pink), with the exception of phenolphthalein (does not react to acids, remains colorless).
2. Interaction with metals in the activity series to the left of hydrogen (subject to the formation of a soluble salt):
acid + metal = salt + hydrogen.
When interacting with metals, the exceptions are oxidizing acids - nitric and concentrated sulfuric acids. Firstly, they also react with some metals that are to the right of hydrogen in the activity series. Secondly, the reaction with metals never releases hydrogen, but produces a salt of the corresponding acid, water and the reduction products of nitrogen or sulfur, respectively.
3. Interaction with bases/amphoteric hydroxides:
acid + base = salt + water.
4. Interaction with ammonia:
acid + ammonia = ammonium salt
5. Interaction with salts (subject to the formation of gas or sediment):
acid + salt = salt + acid.
Polybasic acids are capable of forming not only intermediate, but also acidic salts.
Insoluble silicic acid does not change the color of indicators (a very weak acid), but is capable of reacting with alkali solutions with slight heating:
1. Interaction of silicic acid with alkali solution:
silicic acid + alkali = salt + water.
2. Decomposition (during long-term storage or heating)
silicic acid = silicon(IV) oxide + water.
Chemical properties of amphoteric hydroxides.
Amphoteric hydroxides are capable of forming two series of salts, since when reacting with alkalis they exhibit the properties of an acid, and when reacting with acids they exhibit the properties of a base.
Let's consider the chemical properties of amphoteric hydroxides:
1. Interaction with alkalis:
amphoteric hydroxide + alkali = salt (+ water).
2. Interaction with acids:
amphoteric hydroxide + acid = salt + water.