Inorganic Functions: Acids, Bases, Salts and Oxides

Inorganic functions are groups of inorganic compounds that have similar characteristics.

A fundamental classification in relation to chemical compounds is: organic compounds are those that contain carbon atoms, while organic compounds contain carbon atoms. inorganic compounds they are formed by the other chemical elements.

There are exceptions such as CO, CO₂ and on₂CO₃, which despite having carbon in the structural formula, have characteristics of inorganic substances.

The four main inorganic functions are: acids, bases, salts and oxides.

These 4 main functions were defined by Arrhenius, a chemist who identified ions in acids, bases and salts.

Acids

Acids they are covalent compounds, that is, they share electrons in their bonds. They have the ability to ionize in water and form charges, releasing H⁺ as the only cation.

Classification of acids

Acids can be classified according to the amount of hydrogen that is released into an aqueous solution and ionize, reacting with water to form the hydronium ion.

Number of ionizable hydrogens
Monoacids: they have only one ionizable hydrogen. Examples: HNO3, HCl and HCN
diacids: have two ionizable hydrogens. Examples: H2ONLY4, H2S and H2MnO4
Triacids: have three ionizable hydrogens. Examples: H3DUST4 and H3BO3
tetracids: have four ionizable hydrogens. Examples: H4P7O7

The strength of an acid is measured by the degree of ionization. The higher the value of stronger is the acid because:

degree of ionization
strong: have a degree of ionization greater than 50%.
moderate: have a degree of ionization between 5% and 50%.
weak: have a degree of ionization below 5%.

Acids may or may not contain the element oxygen in their structure, thus:

presence of oxygen
Hidracids: do not have oxygen atoms. Examples: HCl, HBr and HCN.
oxyacids: The element oxygen is present in the acid structure. Examples: HClO, H2CO3 and HNO3.

Acid nomenclature

The general formula of an acid can be described as H_xTHE, where A represents the anion that makes up the acid and the nomenclature generated can be:

anion termination	Acid Termination
etho Example: Chloride (Cl^-)	hydric Example: hydrochloric acid (HCl)
act Example: chlorate	ich Example: chloric acid (HClO3)
very Example: nitrite	bone Example: nitrous acid (HNO2)

Characteristics of acids

The main characteristics of acids are:

• They taste sour.
• They carry electrical current, as they are electrolytic solutions.
• They form hydrogen gas when they react with metals such as magnesium and zinc.
• Form carbon dioxide when reacting with calcium carbonate.
• They change the acid-base indicators to a specific color (blue litmus paper turns red).

Main acids

Examples: hydrochloric acid (HCl), sulfuric acid (H₂ONLY₄), acetic acid (CH₃COOH), carbonic acid (H₂CO₃) and nitric acid (HNO₃).

Although acetic acid is an acid from Organic Chemistry, it is important to know its structure because of its importance.

Bases

Bases are ionic compounds formed by cations, mostly metals, which dissociate in water releasing the hydroxide anion (OH^-).

Base classification

Bases can be classified according to the number of hydroxyls released into solution.

Number of hydroxyls
Monobases: they have only one hydroxyl. Examples: NaOH, KOH and NH4oh
Dibases: have two hydroxyls. Examples: Ca(OH)2, Fe(OH)2 and Mg(OH)2
Tribases: have three hydroxyls. Examples: Al(OH)3 and Fe(OH)3
tetrabases: have four hydroxyls. Examples: Sn(OH)4 and Pb(OH)4

Bases are generally ionic substances and the strength of a base is measured by the degree of dissociation.

The higher the value of stronger is the base because:

dissociation degree
strong: they have a degree of dissociation practically 100%. Examples: Alkali metal bases such as NaOH and KOH. Alkaline earth metal bases such as Ca(OH)2 and Ba(OH)2. Exceptions: Be (OH)2 and Mg(OH)2
weak: have a degree of dissociation less than 5%. Example: NH4OH and Zn(OH)2.

Solubility in water
Soluble: alkali metal and ammonium bases. Examples: Ca(OH)2, Ba(OH)2 and NH4Oh.
Slightly soluble: alkaline earth metal bases. Examples: Ca(OH)2 and Ba(OH)2.
practically insoluble: other bases. Examples: AgOH and Al(OH)3.

Base nomenclature

The general formula of a base can be described as , where B represents the positive radical that makes up the base and y is the charge that determines the number of hydroxyls.

The nomenclature for bases with fixed load is given by:

Bases with fixed load
alkali metals	lithium hydroxide	LiOH
Alkaline Earth Metals	magnesium hydroxide	Mg(OH)2
Silver	silver hydroxide	AgOH
Zinc	zinc hydroxide	Zn(OH)2
Aluminum	aluminum hydroxide	Al(OH)3

When the base has a variable load, the nomenclature can be in two ways:

Bases with variable load
Copper	Ass^+	copper hydroxide I	CuOH
cuprous hydroxide
Ass^2+	copper hydroxide II	Cu(OH)2
cupric hydroxide
Iron	Faith^2+	Iron hydroxide II	Fe(OH)2
ferrous hydroxide
Faith^3+	Iron hydroxide III	Fe(OH)3
ferric hydroxide

Characteristics of the bases

• Most bases are insoluble in water.
• Conduct electric current in aqueous solution.
• They are slippery.
• They react with acid to form salt and water as products.
• They change the acid-base indicators to a specific color (red litmus paper turns blue).

Main bases

Bases are widely used in cleaning products and also in chemical industry processes.

Examples: sodium hydroxide (NaOH), magnesium hydroxide (Mg (OH)₂), ammonium hydroxide (NH₄OH), aluminum hydroxide (Al(OH)₃) and calcium hydroxide (Ca(OH)₂).

salts

salts are ionic compounds that have at least one cation other than H⁺ and an anion other than OH^-.

A salt can be obtained in a neutralization reaction, which is the reaction between an acid and a base.

The reaction of hydrochloric acid with sodium hydroxide produces sodium chloride and water.

The salt formed is composed of the acid anion (Cl^-) and by the base cation (Na⁺).

Classification of salts

Below, we have the main families of salts that can be classified according to water solubility and pH change of the solution as follows:

Water solubility of the most common salts
Soluble	Nitrates		Exceptions: Silver acetate.
Chlorates
Acetates
Chlorides		Exceptions:
Bromides
Iodides
Sulphates		Exceptions:
Insoluble	Sulfides		Exceptions: Alkali metal sulphides, alkaline earth and ammonium.
Carbonates		Exceptions: Those of alkali metals and ammonium.
Phosphates

pH
neutral salts	When dissolved in water they do not change the pH. Example: NaCl.
acid salts	When they are dissolved in water they make the solution pH less than 7. Example: NH4Cl.
basic salts	When they are dissolved in water they make the solution pH greater than 7. Example: CH3COONa.

In addition to the salt families we saw earlier, there are other types of salts, as shown in the table below.

Other types of salts
hydrogen salts	Example: NaHCO3
Hydroxy-salts	Example: Al(OH)2Cl
double salts	Example: KNaSO4
hydrated salts	Example: CuSO4. 5 hours2O
complex salts	Example: [Cu (NH3)4]ONLY4

Nomenclature of salts

In general, the nomenclature of a salt follows the following order:

anion name	cation name	name of salt
Cl^- Chloride	Faith^3+ Iron III	FeCl3 Iron Chloride III
Sulfate	At^+ Sodium	At2ONLY4 Sodium Sulfate
Nitrite	K^+ Potassium	KNO2 Potassium nitrite
br^- Bromide	Here^2+ Calcium	CaBr2 calcium bromide

Characteristics of salts

• They are ionic compounds.
• They are solid and crystalline.
• Suffer from boiling at high temperatures.
• Conduct electric current in solution.
• They taste salty.

Main salts

Examples: potassium nitrate (KNO₃), sodium hypochlorite (NaClO), sodium fluoride (NaF), sodium carbonate (Na₂CO₃) and calcium sulfate (CaSO₄).

Oxides

Oxides are binary compounds (ionic or molecular) that have two elements. They have oxygen in their composition, which is their most electronegative element.

The general formula for an oxide is , where C is the cation and its charge y becomes an index in the oxide forming the compound:

Classification of oxides

According to chemical bonds
Ionic	Combination of oxygen with metals. Example: ZnO.
Molecular	Combination of oxygen with non-metallic elements. Example: OS2.

According to properties
Basics	In aqueous solution they change the pH to greater than 7. Example: I read2O (and other alkali and alkaline earth metals).
Acids	In aqueous solution they react with water and form acids. Examples: CO2, ONLY3 and NO2.
Neutrals	Some oxides that do not react with water. Example: CO.
Peroxides	In aqueous solution they react with water or diluted acids and form hydrogen peroxide H2O2. Example: Na2O2.
Amphoters	They can behave like acids or bases. Example: ZnO.

Nomenclature of oxides

In general, the nomenclature of an oxide follows the following order:

Name according to type of oxide
ionic oxides	Examples of fixed charge oxides: CaO - calcium oxide Al2O3 - aluminum oxide
Examples of oxides with variable charge: FeO - Iron Oxide II Faith2O3 - Iron oxide III
molecular oxides	Examples: CO - carbon monoxide N2O5 - Dinitrogen pentoxide

Oxide characteristics

• They are binary substances.
• They are formed by the binding of oxygen with other elements, except fluorine.
• Metal oxides, when reacting with acids, form salt and water.
• Non-metallic oxides, when reacting with bases, form salt and water.

Main oxides

Examples: calcium oxide (CaO), manganese oxide (MnO₂), tin oxide (SnO₂), iron oxide III (Fe₂O₃) and aluminum oxide (Al₂CO₃).

Entrance Exam Exercises

1. (UEMA/2015) NO₂and the OS₂ are gases that cause atmospheric pollution that, among the damage caused, result in the formation of of acid rain when these gases react with water particles present in clouds, producing HNO₃ and H₂ONLY₄.

These compounds, when carried by atmospheric precipitation, generate disturbances, such as contamination of drinking water, corrosion of vehicles, historical monuments, etc.

The inorganic compounds mentioned in the text correspond, respectively, to the functions:

a) salts and oxides
b) bases and salts
c) acids and bases
d) bases and oxides
e) oxides and acids

See Answer

Correct alternative: e) oxides and acids.

Oxides are compounds formed by oxygen and other elements, except fluorine.

Acids, when they come into contact with water, undergo ionization and produce the hydronium ion. For the acids in question, we have the following reactions:

the HNO₃ it is monoacid because it has only one ionizable hydrogen. the H₂ONLY₄ it is a diacid because it has two ionizable hydrogens.

The other inorganic functions present in the questions correspond to:

Bases: hydroxyl ions (OH^-) ionically bonded with metal cations.

Salts: product of the neutralization reaction between an acid and a base.

Learn more aboutchemical functions.

2. (UNEMAT/2012) We make use of various chemical products in our daily lives, such as magnesium milk, vinegar, limestone and caustic soda.

It is correct to state that these substances mentioned belong, respectively, to the chemical functions:

a) acid, base, salt and base
b) base, salt, acid and base
c) base, acid, salt and base
d) acid, base, base and salt
e) salt, acid, salt and base

See Answer

Correct alternative: c) base, acid, salt and base.

Magnesium milk, limestone and caustic soda are examples of compounds that contain inorganic functions in their structures.

Vinegar is an organic compound formed by a weak carboxylic acid.

In the table below we can observe the structures of each one of them and the chemical functions that characterize them.

Product	Magnesium milk	Vinegar	Limestone	Caustic soda
Chemical compost	magnesium hydroxide	Acetic Acid	Calcium carbonate	Sodium hydroxide
Formula
chemical function	Base	carboxylic acid	salt	Base

Magnesium milk is a suspension of magnesium hydroxide used to treat stomach acid, as it reacts with hydrochloric acid from gastric juice.

Vinegar is a widely used condiment mainly in food preparation due to its aroma and flavor.

Limestone is a sedimentary rock, whose main ore is calcite, which contains large amounts of calcium carbonate.

Caustic soda is the trade name for sodium hydroxide, a strong base used in many industrial processes and household use to unclog pipes due to an accumulation of oils and grease.

3. (UDESC/2008) Regarding hydrochloric acid, it can be said that:

a) when in aqueous solution, it allows the passage of electric current
b) is a diacid
c) is a weak acid
d) has a low degree of ionization
e) is an ionic substance

See Answer

Correct alternative: a) when in aqueous solution, it allows the passage of electric current.

Hydrochloric acid is a monoacid as it has only one ionizable hydrogen.

It is a molecular compound, with a high degree of ionization and therefore it is a strong acid, which, when entering into contract with water, breaks its molecule into ions as follows:

As Arrhenius observed in his experiments, the positive ions formed in ionization move towards the negative pole, while the negative ions move towards the positive pole.

In this way, electrical current flows into the solution.

For more issues with commented resolution, see also: exercises on inorganic functions.