Swedish Svante Arrhenius, in 1884 proposed the principle of acid and also base based upon the theory of ionization. Follow to Arrhenius, the acids space the hydrogen-containing compounds which provide H+ ions or protons on dissociation in water and also bases room the hydroxide compound which give OH− ions on dissociation in water. This concept is just applicable come those compounds which dissolved in aqueous systems (or you deserve to say whereby water is the solvent). The covers many common acids, bases and also their chemical reactions, yet there are likewise other compound that have the features of acids and also bases however they perform not fit right into Arrhenius concept.

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acids and basesArrhenius acid-base theorythe water-ion systemamphoteric nature of waterhydrogen or hydronium ion

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Shikha MunjalDepartment the Chemistry, institution of basic Sciences, Jaipur nationwide University, IndiaAakash Singh*Department of Chemistry, institution of basic Sciences, Jaipur nationwide University, IndiaDepartment that Chemistry, Suditi an international Academy, India

*Address all correspondence to: aakashsingh.ucst

DOI: 10.5772/bsci-ch.org.88173

From the Edited Volume


CorrosionEdited by Ambrish Singh

Edited by Ambrish Singh

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1. Introduction

The principle of acids and also bases have been characterized many times in different ways. Numerous scientists put various meanings to characterize the acids and also bases in which several of the principles are quite narrow and also some are comprehensive. Acids and also bases room existing everywhere in our everyday life. Every liquid other than water, that us used having actually acid and an easy properties, because that example, vinegar (contains acetic acid), soft drink (contains carbonic acid), buttermilk (contains lactic acid), soap (contains base). The earliest meanings were do on the communication of their taste and also their effect on other substances.

1.1 Acids

Acid room those building materials which have sour in taste, spicy odor, corrosive, having pH2. Because that example, the reaction in between sodium hydroxide (base) and hydrochloric acid, creates sodium chloride (salt) and water.


1.2 determinants affecting acidic strength

The stamin of acids and also bases relies on following factors:Polarity the the molecule and strength the H▬A bond

Electro negativity


1.2.1 Polarity of the molecule and strength the H▬A bond

As the polarity of the molecule increases, the electron density will gain away from hydrogen atom and it i do not care H+ (proton). The better is the positive charge ~ above the hydrogen atom, H▬A link will become weaker, lesser is the power required to break it. Then, the proton will quickly dissociate in the solution. Hence, it will certainly be the strong acid <1>.

* vital points

The priority should be provided to the polarity the H▬A bond, once we to compare the acidic strength of facets in the very same row. However when us compare the acidic toughness of aspects of same team of routine table, then priority is given to stamin of H▬A bond.

1.2.2 Electro negativity

The hydrogen is connect to the more electronegative atom is much more acidic. For example - the hydrogen is attached come the oxygen (E.N=3.5) is an ext acidic than the hydrogen attached come nitrogen (E.N=3.0, i beg your pardon is much less electronegative than oxygen).

1.2.3 Size

The dimension of “A” atom influence the mountain of acidic strength. Together the size of the atom increases, the bond becomes weaker and acidic strength boosts <2>.

1.2.4 Hybridization

Hybridization plays an essential role in determining the acidic strength. Together the hybridization move from sp3 come sp, the “s” personality increases, therefore acidic stamin increases.

1.3 Bases

Bases space those building materials which have bitter taste, odorless, rotate red litmus blue, having actually pH much more than 7 and becomes much less alkaline when react through acid. These room violent and also less reactive 보다 acids. For example, NaOH (Sodium hydroxide), LiOH (Lithium hydroxide), KOH (potassium hydroxide), etc.

These room the basic properties of mountain or bases, yet not true for every solitary acid or base. There are some necessary concepts:Arrhenius acid-base theory

Lewis acid-base concept

Bronsted-Lowry concept

Lux-flood concept

Solvent-system concept


2. The Arrhenius acid-base theory (the water-ion system)

The Arrhenius acid-base concept was proposed by sweden Svante Arrhenius. It was the an initial modern approach to acid-base concept. This theory is quite simple and useful. According to Arrhenius theory, acids are the link that rises the concentration the H+ or proton in aqueous solution. The released H+ ion or proton is no free-floating proton, it exist in combined state v the water molecule and also forms hydronium ion (H3O+). The typical examples that Arrhenius acid has HCl (hydrochloric acid), H2SO4 (sulphuric acid), HNO3 (nitric acid), etc. As displayed in Table 1.


Arrhenius acid formulaName
HClO3Chloric acid
HNO3Nitric acid
HClO4Perchloric acid
H3PO4Phosphoric acid
H2SO4Sulphuric acid
H2SO3Sulfurous acid
HClHydrochloric acid
CH3COOHAcetic acid
HBrHydrobromic acid

Table 1.

Some Arrhenius acids.

When the is liquified in water, then:


The acids favor HNO3, HCl, etc. Offers one proton ~ above dissociation, dubbed monoprotic acids. The acids choose H2SO4, H3PO4, etc. Which having more than one hydrogen atoms and gives an ext than 1 H+ ions on dissociation, referred to as polyprotic acids. The is not necessary that polyprotic acids room stronger 보다 monoprotic acids.


Similarly, Arrhenius bases room compounds that rise the concentration that OH− or hydroxide ion in aqueous systems or having at the very least one OH− ion in formula. The common examples of Arrhenius base consists of NaOH (sodium hydroxide), KOH (potassium hydroxide), Ca(OH)2 (calcium hydroxide), Mg(OH)2 (magnesium hydroxide), NH4OH (ammonium hydroxide), etc. As displayed in Table 2.

Arrhenius baseName
NaOHSodium hydroxide
NH4OHAmmonium hydroxide
KOHPotassium hydroxide
Mg(OH)2Magnesium hydroxide
Ca(OH)2Calcium hydroxide
Al(OH)3Aluminum hydroxide

Table 2.

Some Arrhenius bases.

When salt hydroxide liquified in water, it totally dissociates into ions Na+ and OH−, this dissociation increases the concentration of hydroxide ions in the solution.

2.1 Neutralization reaction

When Arrhenius acid and Arrhenius base reacts, salt and water is formed as product, the reaction is recognized as neutralization reaction. Because that example:

The acids which are fully ionized in aqueous solution, is termed as solid acids such as HCl, HNO3, H2SO4, etc.

Hydrochloric mountain is a solid acid. When it dissociates right into water, hydronium ion and chloride ion are created as product. Chloride ions room weak base, yet its basicity does no make the solution basic because acidity is overpowering the basicity the chloride ions. The H+ ions integrate with water molecule and type hydronium ion. In case of solid acid, the concentration of hydronium ion developed is equal to the concentration of the mountain whereas in instance of weak acids, the concentration the hydronium ion in solution is constantly less 보다 the concentration that hydrogen ions.

Whereas the mountain which space weakly ionized in aqueous solution, is termed as weak mountain such as acetic mountain (CH3COOH).

In situation of weak acids, the concentration the hydronium ion is always less than the concentration the acid.

Similarly, bases i beg your pardon are completely ionized in aqueous solution, are termed as strong bases such together NaOH, KOH, etc. Whereas the bases which space weakly ionized in aqueous solution, is known as weak bases such together ammonium hydroxide (NH4OH), calcium hydroxide (Ca(OH)2), etc.

Note: that is not necessary that solid acids/bases room concentrated and weak acids/bases room dilute. Because, the dissociation that a substance does not depend on its concentration.


3. Utility of Arrhenius concept

This concept explains numerous phenomena like strength the acids and bases, salt hydrolysis and also neutralization.


4. Hydrogen ion (H+) or hydronium ion (H3O+)

When electron is removing from hydrogen atom, hydrogen ion H+ is formed which is really reactive. However this H+ ion does no exist in aqueous solution. Because in aqueous medium, that reacts v water molecule and also forms hydronium ion (H3O+). Water is a polar molecule; it has the capacity to lure the hydrogen ion (H+). The water includes hydrogen and oxygen in which oxygen (EN=3.5) is an ext electronegative the pulls the electron thickness towards it and causing the partial an adverse charge ~ above the molecule. Due to partial negative charge, it has capacity to entice the positively charged hydrogen ion (H+) and type hydronium ion (H3O+). Hydronium ion are more stable than hydrogen ions.

The hydronium ion is very important variable in chemical reaction that occurs in aqueous services <3>. The is created by the protonation the water.


5. Concept of pH

The pH that solution have the right to be determined by the concentration that hydronium ion.

pH=−log (H3O+)

From this equation, us can discover the pH that pure water. The pH the pure water concerns be 7 that is thought about to it is in neutral. The solution is either acidic or an easy depending on the adjust in the concentration the hydronium ion.

According to number 1:If the concentration of the hydronium ion in the equipment increases means more than 10−7mol/l, pH rises that makes the solution more acidic.

If the concentration of the hydronium ion in the solution decreases way −7mol/l, pH to reduce that makes the solution much more basic.

Figure 1.

pH scale.


6. Amphoteric nature the water

The word amphoteric is acquired from Greek word “amphi” that means both (acid and base). Amphoteric substances room those that has actually potential come act either as an mountain or base. Because that example: H2O (water) <3>.

On dissociation, that ionizes into H+ and also OH− (hydroxide) ion. The visibility of H+ shows an acid and also the presence of OH− ion shows a base. Since, water is a neutral molecule. So, the dissociates equally into H+ and OH− ion.

According to Arrhenius acid-base theory:

The amphoteric nature that water is very important due to the fact that most that the acid-base chemical reactions takes location in the visibility of water. Water is important amphoteric compound that deserve to act together both one Arrhenius acid or Arrhenius base.

Auto-ionization that water <4>;

The H+ ion (a ceiling proton) does not exist in the solution, it forms hydronium ions by hydrogen bonding through nearest water molecule. Many books refers the “concentration that hydrogen ions” i m sorry is not correct. Because there room no H+ ions, just hydronium ions in the solution. Technically, the number of hydronium ions created is equal to the variety of hydrogen ion. So, both can be used.


7. Advantages of Arrhenius theory

This concept is used to explains:Strength that acid and also bases

The strength of Arrhenius acid and also Arrhenius base can be established by the extent to which the dissociate to provide H+ ion or hydroxide ion <5>.The nature of acids and bases in aqueous medium.

Neutralization of acid by reaction v base


8. Limitation that Arrhenius acid-base theory

This theory is an extremely limited, out of three theories. According to this theory, the solution medium should it is in aqueous and also acid should create hydrogen ion (H+) or base should produce hydroxide ion (OH−) ~ above dissociation through water. Hence, the problem is pertained to as Arrhenius mountain or Arrhenius base when it is dissolved in water. Because that example, HNO3 is concerned as Arrhenius acid once it is dissolved in aqueous solution. However when it is liquified in any kind of other solvent like benzene, no dissociation occurs. This is against the Arrhenius theory.

Arrhenius theory is not applicable top top the non-aqueous or gaseous reactions because it described the acid-base actions in terms of aqueous solutions.

In Arrhenius theory, salts are create in the product which room neither acidic nor basic. So, this concept cannot explain the neutralization reaction without the existence of ions. Because that example, once acetic acid (weak acid) and also sodium hydroxide (strong base) reacts, climate the resulting equipment basic. But this principle is not explained by Arrhenius.

Arrhenius theory is just applicable to those compounds which having formula HA or BOH because that acids and bases. There room some acids prefer AlCl3, CuSO4, CO2, SO2 which cannot be stood for by HA formula, this concept is unable to describe their acidic behavior. Similarly, there room some bases favor Na2CO3, NH3, etc. Which do not stood for by BOH formula, this concept is can not to describe their simple behavior.


9. Bronsted-Lowry theory

We have been previously learned one Arrhenius acid-base concept which listed a great start in the direction of the acid-base chemistry but it has details limitations and problems. After ~ this theory, a Danish chemist, called Johannes Nicolaus Bronsted and also British scientist, cutting board Martin Lowry suggest a different an interpretation of acid-base that based upon the abilities of link to either donate or expropriate the protons. This concept is recognized as Bronsted-Lowry theory, likewise called Proton theory of acid and also base. This theory offers a much more general and useful acid-base an interpretation and uses to wide variety of chemistry reactions. In this theory, us usually take into consideration a hydrogen atom together a proton that has actually lost that electrons and becomes a positively fee hydrogen ion (represented by symbol, H+).

According come Bronsted-Lowry concept, an acid is considered to be Bronsted-Lowry acid which is capable to donate a proton to who else. A basic is thought about to it is in Bronsted-Lowry basic which is capable to expropriate a proton from who else. From here, it can note that as soon as an acid reacts v a base, the proton is transferred from one chemical varieties to another.Bronsted-Lowry acid-Hydrogen ion (Proton) donor.

Bronsted-Lowry base-Hydrogen ion (Proton) acceptor.

9.1 Conjugate acid-base pairs

Conjugate acid: It forms when a base accepts proton.

Conjugate base: It creates when an acid donates proton.

Note: If an acid is strong, the conjugate base will be weaker and if the basic is strong, the conjugate acid will certainly be weak.

Consider the following chemical reaction:

In this reaction, HCl is one acid because it is donating proton come NH3. Therefore, HCl is act as Bronsted-Lowry mountain whereas NH3 has actually a lone pair of electrons which is provided to accept the protons. Therefore, NH3 is act as Bronsted-Lowry base. This reaction is reversible also. In reversible case, the ammonium ion reacts through chloride ion and again converts right into ammonia (NH3) and hydrogen chloride (HCl). In this case, the ammonium ion is donating a proton, called conjugate acid. The chloride ion (Cl−) ion is accepting a proton, referred to as conjugate base.

There room two conjugate pairs—conjugate pair 1 and conjugate pair 2.Conjugate pair 1: HCl and Cl−

Conjugate pair 2: NH3 and also NH4+

From that equation, the ammonium ion (NH4+) is a conjugate mountain of base ammonia and chloride ion (Cl−) is a conjugate basic of mountain hydrogen chloride.

Note: according to the concept of Arrhenius, the reaction between HCl and NH3 is not considered as acid-base reaction since none that these species gives H+ and OH− ions in water.

9.2 instances of Bronsted-Lowry acids and also bases

In this reaction, the nitric acid donates a proton to the water, therefore it act together a Bronsted-Lowry acid. Since, water accepts a proton indigenous nitric acid, so it is act as Bronsted-Lowry base. In this reaction, the arrow is attracted only to the appropriate side which means that reaction highly favours the formation of products.

In this reaction, the water is losing its proton, i do not care hydroxide (OH−) and also donates its proton to the ammonia. Therefore, water is act as Bronsted-Lowry acid. Ammonia is agree a proton native the water, forms ammonium ion (NH4+). Therefore, ammonia is act together Bronsted-Lowry base.

From the above two reactions, we have the right to conclude that the water is Amphoteric in nature which means that it deserve to act as both: Bronsted-Lowry acid and Bronsted-Lowry base.

9.3 advantages of Bronsted-Lowry theory

This theory is may be to describe the acid-base habits in aqueous and also non-aqueous medium.

It describes the straightforward character of substances favor NH3, CaO, Na2CO3, the is, which carry out not save −OH group however according come Arrhenius theory, they are not taken into consideration as bases.

It describes the acidic personality of substances prefer CO2, SO2, etc. Which do not save on computer hydrogen ion group yet according come Arrhenius theory, they room not thought about as acids.

This theory likewise explains the acid-base behavior of ionic species.

9.4 flaw of Bronsted-Lowry theory

According come Bronsted-Lowry theory, exact same compound is action as mountain in one reaction and also act as base in other reaction. So, occasionally it is very an overwhelming to guess the exact acid or basic in a reaction.

This concept is not able to explain the acidic, straightforward as well as Amphoteric gaseous molecule.

This theory does not explain the behavior of acids favor BF3, AlCl3, BCl3, etc. Which perform not proton to loose or donate.

This theory does not explain reactions between acidic oxides (CO2, SO2, SO3) and basic oxides (CaO, MgO, BrO) i m sorry takes ar in the absence of solvent.


11. Lewis acid-base theory

The Bronsted-Lowry concept which we have actually been previously studied to be a an excellent startup because that acid-base chemistry. The Bronsted-Lowry ide was based upon the transport of proton from one chemical varieties to another. Yet this concept has certain limitations. UC Berkeley scientist, G.N. Lewis, in 1923 proposed a new acid-base concept which is based on their transfer of electrons. This concept is more advanced and also flexible 보다 Bronsted-Lowry since it defines the acid-base habits in the molecules which execute not save hydrogen ions or in non-aqueous medium.

11.1 Lewis acid

According to this theory, an mountain is a problem which has ability to expropriate the non-bonding pair that electrons, called Lewis acid. They are periodically referred as electron deficient types or electrophile.

11.1.1 Lewis acid: characteristics

Lewis acid-electron-pair acceptor.

Lewis acid should have a vacant or empty orbital.

All cations (Na+, Cu2+, Fe3+) room Lewis acids because they have ability to expropriate a pair the electrons but all Lewis acids are not cations.

More is the optimistic charge top top the metal, an ext is the acidic character. Fe3+ is an excellent Lewis acid than Na+.The ion, molecule or one atom which has actually incomplete octet of electrons are additionally Lewis acids.

For example: BF3.

Here, you deserve to see the the central atom boron has six electrons in that outermost shell. So, it has ability to accept more electrons because of the visibility of an empty orbital and also hence, act together Lewis acid.

The molecule in i beg your pardon the main atom has an ext than eight electron (SiF4, SiBr4), are also considered together Lewis acids.

The molecule prefer CO2, SO2, etc. Are also considered as Lewis acid. These species of molecules kind multiple bond in between the atoms of different electronegativity. In situation of change metal ions, the steel having much more electronegativity provides stronger Lewis acids.

Electron bad п: device is also considered together Lewis acids, because that example, +, etc.

11.2 Lewis base

A basic is a substance which has ability to donate the electrons, referred to as Lewis base. Lock are occasionally referred together electron rich species or Nucleophile.

11.2.1 Lewis base: characteristics

Lewis base-electron-pair donor

All steel anions (F−, Cl−, Br−, I−) are Lewis base due to the fact that they have capability to donate the electron yet all Lewis bases are not anions.

The ion, molecule or an atom which having actually a lone pair the electrons, are additionally considered together Lewis base.

The electron-rich п mechanism is also considered as Lewis bases, because that example, benzene, ethene, etc.

The toughness of the Lewis base deserve to be raised by increasing the electron density.

Note: as soon as a Lewis mountain reacts v Lewis base, then Lewis acid uses its shortest unoccupied molecular orbital (LUMO) and also base supplies its highest occupied molecular orbit (HUMO) to develop a bonded molecular orbital. Actually, Lewis acid and also Lewis base both have actually LUMO and also HUMO but HUMO is constantly considered as base and also LUMO is always considered together acid.

11.4 Neutralization reaction between Lewis acid and also Lewis base

When a Lewis acid reacts with a Lewis base, climate a Lewis acid-base reaction wake up in which the molecule i m sorry act together Lewis basic donate that electron pair into the north orbital of one acid, forms Lewis acid-base adduct as displayed in figure 2. The adduct formed contains a covalent name: coordinates bond between Lewis acid and Lewis base. The over explanation means that the Lewis acid is a low electron density centre and Lewis base is a high electron density centre <6>.

Figure 2.

Acid-base neutralization.

In this reaction, the 2 ammonia molecule reacts v silver ion. The ammonia has actually lone pair of electrons, for this reason it has actually the capability to donate the lone pairs of electrons and acts as Lewis base. The optimistic charge on silver denotes its electrophilic nature that means it has actually an capability to accept the pairs of electrons and act together Lewis mountain (by Lewis definition).

Here, that can also be provided that when a Lewis mountain reacts v a Lewis base, over there is no adjust in the oxidation variety of any of this atoms.

11.5 limitations of Lewis acid-base theory

This concept is not able to describe that why all acid-base reactions perform not show off the covalent coordination bond.

This concept is also unable to define the habits of some acids prefer hydrogen chloride (HCl) and sulfuric mountain (H2SO4) because they carry out not form the covalent coordination bond through bases. Hence, they space not taken into consideration as Lewis acids.

This concept cannot define the ide that why the development of coordination shortcut is a slow process and acid-base reactions is a rapid process.

This theory cannot describe the principle of relative strength of acids and bases.

This theory stops working to describe the catalytic activity of some Lewis acids.

12. Relation in between Lewis acid-base theory and also Arrhenius theory

All Arrhenius acids and also Bronsted Lowry acids room Lewis acids but reverse is no true.

13. Conclusion

Acids and bases are an extremely important for modern-day society and also in our daily lives. They exist anywhere in our body and in ours surroundings. The concept that has actually been described in this thing has offered us all the simple information the acids and bases. In this chapter, we have discussed all the three an easy theory of acid-base chemistry-Arrhenius theory, Bronsted-Lowry theory and Lewis acid-base theory. Acids and bases have crucial role in the area of medicine. Indigenous this concept, that is currently easy to treat the conditions with the enhanced medicines by complicated understanding of acids and bases. Because that example, If the concentration the hydrogen ion rises in the human being blood, acidity rises that results weakness in body. In the condition, the body have to keep alkaline through digesting food the produces alkali in the body, to neutralize the acidity.

Definitely, without acids or bases information, our stays would look different to exactly how it look at now. Many assets we space using this day would have no use without this knowledge.


I to be eternally grateful and beholden to my family. My mother Mrs. Suman Munjal, father Mr. Bhim Sain Munjal and sister Mrs. Shweta Java because that strengthening me with the opportunities and experiences which allowed me in getting to these heights. The reason behind this success is their selfless encourage that helped me explore brand-new dimensions in my life.

I specifically acknowledge the donation of my confidence Dr. Himanshu Mathur and also brother Mr. Chirag Munjal for his constant and constant support, effective efforts of proof reading my works, type words the motivation, and also providing me with beneficial tips. Ns would choose to present my appreciation for sharing his expertise and experiences for organizing compelled resources.

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I Shikha Munjal undersigned solemnly declare that all the information submitted by me in this chapter is correct, true and valid.