Swedish Svante Arrhenius, in 1884 propose the ide of acid and also base based upon the theory of ionization. Follow to Arrhenius, the acids are the hydrogen-containing compounds which provide H+ ions or proton on dissociation in water and also bases are the hydroxide compounds which offer OH− ions on dissociation in water. This concept is only applicable to those compounds which liquified in aqueous solution (or you deserve to say where water is the solvent). It covers many typical acids, bases and also their chemistry reactions, however there are additionally other link that have the features of acids and also bases yet they execute not fit into Arrhenius concept.

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

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Shikha MunjalDepartment that Chemistry, college of straightforward Sciences, Jaipur national University, IndiaAakash Singh*Department of Chemistry, institution of an easy Sciences, Jaipur national University, IndiaDepartment the Chemistry, Suditi an international Academy, India

*Address every correspondence to: aakashsingh.ucst

DOI: 10.5772/rebab.net.88173

From the Edited Volume


CorrosionEdited by Ambrish Singh

Edited through Ambrish Singh

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1. Introduction

The concept of acids and bases have actually been characterized many times in different ways. Number of scientists put various definitions to characterize the acids and bases in which several of the ideas are fairly narrow and some are comprehensive. Acids and bases space existing all over in our everyday life. Every liquid except water, that us used having actually acid and basic properties, for example, vinegar (contains acetic acid), soft drinks (contains carbonic acid), buttermilk (contains lactic acid), soap (contains base). The earliest meanings were make on the basis of your taste and their result on other substances.

1.1 Acids

Acid are those substances which have actually sour in taste, sharp odor, corrosive, having actually pH2. For example, the reaction between sodium hydroxide (base) and hydrochloric acid, develops sodium chloride (salt) and water.


1.2 components affecting acidic strength

The stamin of acids and also bases counts on adhering to factors:Polarity that the molecule and strength of H▬A bond

Electro negativity


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

As the polarity that the molecule increases, the electron thickness will gain away native hydrogen atom and it i do not care H+ (proton). The higher is the optimistic charge on the hydrogen atom, H▬A shortcut will come to be weaker, lesser is the energy required to break it. Then, the proton will quickly dissociate in the solution. Hence, it will certainly be the solid acid <1>.

* vital points

The priority must be offered to the polarity of H▬A bond, when we to compare the acidic toughness of elements in the very same row. Yet when we compare the acidic toughness of facets of same group of regular table, climate priority is given to toughness of H▬A bond.

1.2.2 Electro negativity

The hydrogen is attach to the much more electronegative atom is an ext acidic. For instance - the hydrogen is attached to the oxygen (E.N=3.5) is more acidic than the hydrogen attached to nitrogen (E.N=3.0, which is less electronegative 보다 oxygen).

1.2.3 Size

The dimension of “A” atom affects the acidity of acidic strength. As the size of the atom increases, the bond becomes weaker and also acidic strength increases <2>.

1.2.4 Hybridization

Hybridization plays crucial role in identify the acidic strength. Together the hybridization moves from sp3 to sp, the “s” character increases, for this reason acidic strength increases.

1.3 Bases

Bases room those substances which have actually bitter taste, odorless, turn red litmus blue, having actually pH more than 7 and also becomes less alkaline when react v acid. These room violent and less reactive than acids. Because that example, NaOH (Sodium hydroxide), LiOH (Lithium hydroxide), KOH (potassium hydroxide), etc.

These space the basic properties of mountain or bases, yet not true for every single acid or base. There room 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 concept (the water-ion system)

The Arrhenius acid-base concept was propose by swedish Svante Arrhenius. It was the first modern technique to acid-base concept. This theory is quite straightforward and useful. Follow to Arrhenius theory, acids space the link that increases the concentration of H+ or proton in aqueous solution. The released H+ ion or proton is not free-floating proton, it exist in linked state with the water molecule and forms hydronium ion (H3O+). The common examples of Arrhenius acid includes HCl (hydrochloric acid), H2SO4 (sulphuric acid), HNO3 (nitric acid), etc. As shown 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 that is dissolved in water, then:


The acids favor HNO3, HCl, etc. Offers one proton top top dissociation, referred to as monoprotic acids. The acids favor H2SO4, H3PO4, etc. Which having an ext than one hydrogen atoms and gives more than 1 H+ ions on dissociation, dubbed polyprotic acids. It is not important that polyprotic acids are stronger than monoprotic acids.


Similarly, Arrhenius bases room compounds that rise the concentration that OH− or hydroxide ion in aqueous solution or having actually at the very least one OH− ion in formula. The common examples the Arrhenius base has NaOH (sodium hydroxide), KOH (potassium hydroxide), Ca(OH)2 (calcium hydroxide), Mg(OH)2 (magnesium hydroxide), NH4OH (ammonium hydroxide), etc. As shown 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 sodium hydroxide dissolved in water, it totally dissociates right into ions Na+ and also OH−, this dissociation boosts the concentration of hydroxide ions in the solution.

2.1 Neutralization reaction

When Arrhenius acid and also Arrhenius base reacts, salt and water is created as product, the reaction is recognized as neutralization reaction. For example:

The mountain which are totally ionized in aqueous solution, is termed as strong acids such together HCl, HNO3, H2SO4, etc.

Hydrochloric mountain is a solid acid. Once it dissociates right into water, hydronium ion and chloride ion are developed as product. Chloride ions room weak base, but its basicity does not make the solution basic because acidity is overpowering the basicity that chloride ions. The H+ ions combine with water molecule and form hydronium ion. In case of strong acid, the concentration that hydronium ion developed is equal to the concentration that the mountain whereas in situation of weak acids, the concentration the hydronium ion in systems is always less 보다 the concentration that hydrogen ions.

Whereas the mountain which room weakly ionized in aqueous solution, is termed together weak acids such together acetic acid (CH3COOH).

In case of weak acids, the concentration of hydronium ion is always less 보다 the concentration of acid.

Similarly, bases i m sorry are fully ionized in aqueous solution, room termed as strong bases such together NaOH, KOH, etc. Whereas the bases which are weakly ionized in aqueous solution, is known as weak bases such together ammonium hydroxide (NH4OH), calcium hydroxide (Ca(OH)2), etc.

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


3. Utility of Arrhenius concept

This concept explains numerous phenomena favor strength of acids and bases, salt hydrolysis and neutralization.


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

When electron is removing from hydrogen atom, hydrogen ion H+ is developed which is really reactive. But this H+ ion does not exist in aqueous solution. Because in aqueous medium, that reacts through water molecule and forms hydronium ion (H3O+). Water is a polar molecule; it has actually the capability to attract the hydrogen ion (H+). The water contains 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 on the molecule. Because of partial an unfavorable charge, the has capability to lure the positively fee hydrogen ion (H+) and form hydronium ion (H3O+). Hydronium ions are more stable than hydrogen ions.

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


5. Principle of pH

The pH the solution deserve to be determined by the concentration of hydronium ion.

pH=−log (H3O+)

From this equation, we can find the pH the pure water. The pH of pure water pertains to be 7 the is thought about to it is in neutral. The systems is one of two people acidic or simple depending ~ above the change in the concentration of hydronium ion.

According to figure 1:If the concentration that the hydronium ion in the equipment increases method more than 10−7mol/l, pH rises that renders the solution an ext acidic.

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

Figure 1.

pH scale.


6. Amphoteric nature the water

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

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

According come Arrhenius acid-base theory:

The amphoteric nature that water is very important due to the fact that most the the acid-base chemical reactions takes ar in the presence of water. Water is necessary amphoteric compound that have the right to act as both one Arrhenius acid or Arrhenius base.

Auto-ionization of water <4>;

The H+ ion (a ceiling proton) does not exist in the solution, it creates hydronium ion by hydrogen bonding with nearest water molecule. Many books refers the “concentration the hydrogen ions” which is no correct. Due to the fact that there are no H+ ions, just hydronium ion in the solution. Technically, the variety of hydronium ions developed is same to the number of hydrogen ion. So, both can be used.


7. Benefits of Arrhenius theory

This concept is offered to explains:Strength that acid and bases

The stamin of Arrhenius acid and Arrhenius base deserve to be identified by the degree to which it dissociate to offer H+ ion or hydroxide ion <5>.The nature of acids and also bases in aqueous medium.

Neutralization of acid by reaction v base


8. Limitation the Arrhenius acid-base theory

This theory is an extremely limited, the end of three theories. Follow to this theory, the solution medium should be aqueous and acid should create hydrogen ion (H+) or base should develop hydroxide ion (OH−) ~ above dissociation v water. Hence, the substance is regarded as Arrhenius acid or Arrhenius base once it is liquified in water. For example, HNO3 is pertained to as Arrhenius acid once it is liquified in aqueous solution. But when that is dissolved in any type of other solvent favor benzene, no dissociation occurs. This is versus the Arrhenius theory.

Arrhenius concept is no applicable top top the non-aqueous or gas reactions due to the fact that it defined the acid-base actions in terms of aqueous solutions.

In Arrhenius theory, salt are produce in the product which room neither acidic nor basic. So, this theory cannot explain the neutralization reaction without the visibility of ions. Because that example, when acetic mountain (weak acid) and also sodium hydroxide (strong base) reacts, then the resulting systems basic. Yet this principle is not defined by Arrhenius.

Arrhenius theory is only applicable to those compounds which having actually formula HA or BOH for acids and also bases. There space some acids favor AlCl3, CuSO4, CO2, SO2 which cannot be stood for by HA formula, this concept is can not to explain their acidic behavior. Similarly, there room some bases choose Na2CO3, NH3, etc. Which perform not stood for by BOH formula, this theory is can not to define their an easy behavior.


9. Bronsted-Lowry theory

We have been previously learned one Arrhenius acid-base theory which noted a great start towards the acid-base chemistry but it has certain limitations and problems. After this theory, a Danish chemist, named Johannes Nicolaus Bronsted and British scientist, cutting board Martin Lowry suggest a different definition of acid-base that based upon the abilities of link to one of two people donate or accept the protons. This theory is known as Bronsted-Lowry theory, likewise called Proton theory of acid and base. This theory offers a more general and useful acid-base meaning and uses to wide variety of chemical reactions. In this theory, us usually think about a hydrogen atom together a proton that has lost its electrons and becomes a positively fee hydrogen ion (represented through symbol, H+).

According to Bronsted-Lowry concept, an acid is taken into consideration to it is in Bronsted-Lowry acid which is capable to donate a proton to someone else. A basic is considered to it is in Bronsted-Lowry base which is qualified to expropriate a proton from someone else. From here, it can note that when an mountain reacts through a base, the proton is transferred from one chemical types 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 develops when a basic accepts proton.

Conjugate base: It develops when an acid donates proton.

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

Consider the following chemical reaction:

In this reaction, HCl is an acid due to the fact that it is donating proton come NH3. Therefore, HCl is act together Bronsted-Lowry acid whereas NH3 has a lone pair of electrons which is supplied to accept the protons. Therefore, NH3 is act together 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 also 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, dubbed 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 acid of base ammonia and also chloride ion (Cl−) is a conjugate base of mountain hydrogen chloride.

Note: follow to the theory of Arrhenius, the reaction in between HCl and also NH3 is not considered as acid-base reaction because none of these species gives H+ and also OH− ion in water.

9.2 instances of Bronsted-Lowry acids and also bases

In this reaction, the nitric mountain donates a proton come the water, because of this 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 ideal side which means that reaction extremely favours the development of products.

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

From the over two reactions, we can conclude the the water is Amphoteric in nature which means that it can act together both: Bronsted-Lowry acid and also Bronsted-Lowry base.

9.3 advantages of Bronsted-Lowry theory

This concept is able to define the acid-base behavior in aqueous and also non-aqueous medium.

It defines the straightforward character that substances choose NH3, CaO, Na2CO3, the is, which execute not contain −OH group yet according to Arrhenius theory, they space not considered as bases.

It defines the acidic personality of substances favor CO2, SO2, etc. Which perform not contain hydrogen ion group however according come Arrhenius theory, they space not taken into consideration as acids.

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

9.4 disadvantages of Bronsted-Lowry theory

According to Bronsted-Lowry theory, exact same compound is plot as mountain in one reaction and act together base in other reaction. So, occasionally it is very challenging to predict the precise acid or basic in a reaction.

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

This theory does not explain the actions of acids prefer BF3, AlCl3, BCl3, etc. Which perform not protons to loose or donate.

This concept does not describe reactions between acidic oxides (CO2, SO2, SO3) and simple oxides (CaO, MgO, BrO) i m sorry takes ar in the lack of solvent.


11. Lewis acid-base theory

The Bronsted-Lowry theory which we have been formerly studied was a an excellent startup because that acid-base chemistry. The Bronsted-Lowry principle was based on the transport of proton from one chemical species to another. Yet this concept has details limitations. UC Berkeley scientist, G.N. Lewis, in 1923 propose a brand-new acid-base theory which is based on their carry of electrons. This theory is much more advanced and flexible 보다 Bronsted-Lowry because it explains the acid-base behavior in that molecules which carry out not contain hydrogen ions or in non-aqueous medium.

11.1 Lewis acid

According come this theory, an mountain is a problem which has capability to accept the non-bonding pair the electrons, referred to as Lewis acid. They are periodically referred together electron deficient varieties or electrophile.

11.1.1 Lewis acid: characteristics

Lewis acid-electron-pair acceptor.

Lewis acid should have a vacant or north orbital.

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

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

For example: BF3.

Here, you have the right to see the the central atom boron has six electrons in that outermost shell. So, the has capability to accept much more electrons because of the existence of an empty orbital and also hence, act as Lewis acid.

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

The molecule like CO2, SO2, etc. Are additionally considered together Lewis acid. These types of molecules form multiple bond between the atoms of different electronegativity. In instance of shift metal ions, the metal having an ext electronegativity renders stronger Lewis acids.

Electron negative п: system is likewise considered as Lewis acids, for example, +, etc.

11.2 Lewis base

A basic is a problem which has ability to donate the electrons, dubbed Lewis base. Castle are occasionally referred together electron rich types or Nucleophile.

11.2.1 Lewis base: characteristics

Lewis base-electron-pair donor

All metal anions (F−, Cl−, Br−, I−) space Lewis base since they have ability to donate the electron however all Lewis bases space not anions.

The ion, molecule or one atom which having a lone pair of electrons, are likewise considered together Lewis base.

The electron-rich п device is likewise considered together Lewis bases, for example, benzene, ethene, etc.

The toughness of the Lewis base deserve to be boosted by enhancing the electron density.

Note: once a Lewis mountain reacts through Lewis base, climate Lewis acid supplies its shortest unoccupied molecular orbital (LUMO) and base provides its highest possible occupied molecular orbit (HUMO) to produce a bonded molecular orbital. Actually, Lewis acid and also Lewis basic both have actually LUMO and HUMO but HUMO is constantly considered as base and also LUMO is constantly considered as acid.

11.4 Neutralization reaction in between Lewis acid and also Lewis base

When a Lewis mountain reacts through a Lewis base, then a Lewis acid-base reaction occurs in i m sorry the molecule which act together Lewis base donate that electron pair right into the empty orbital of one acid, creates Lewis acid-base adduct as shown in number 2. The adduct formed consists of a covalent name: coordinates bond in between Lewis acid and Lewis base. The above explanation suggests that the Lewis mountain is a short electron density centre and also Lewis base is a high electron density centre <6>.

Figure 2.

Acid-base neutralization.

In this reaction, the two ammonia molecule reacts with silver ion. The ammonia has actually lone pair the electrons, so it has the ability to donate the lone pairs of electrons and acts as Lewis base. The confident charge on silver denotes the electrophilic nature that way it has an capability to accept the bag of electrons and also act as Lewis mountain (by Lewis definition).

Here, the can also be listed that as soon as a Lewis acid reacts through a Lewis base, over there is no change in the oxidation variety of any of this atoms.

11.5 constraints of Lewis acid-base theory

This concept is no able to explain that why all acid-base reactions execute not involve the covalent coordination bond.

This concept is also unable to describe the habits of part acids choose hydrogen chloride (HCl) and sulfuric mountain (H2SO4) because they carry out not form the covalent coordination bond with bases. Hence, they are not thought about as Lewis acids.

This theory cannot explain the principle that why the formation of coordination link is a slow procedure and acid-base reaction is a fast process.

This concept cannot define the concept of family member strength the acids and bases.

This theory fails to describe the catalytic activity of part Lewis acids.

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

All Arrhenius acids and Bronsted Lowry acids are Lewis acids yet reverse is not true.

13. Conclusion

Acids and also bases are an extremely important for modern-day society and in our daily lives. Castle exist almost everywhere in ours body and also in ours surroundings. The theory that has been defined in this chapter has given us every the an easy information the acids and bases. In this chapter, us have disputed all the three basic theory of acid-base chemistry-Arrhenius theory, Bronsted-Lowry theory and Lewis acid-base theory. Acids and also bases have an essential role in the area that medicine. From this concept, the is now easy come treat the diseases with the improved medicines by complicated understanding of acids and bases. For example, If the concentration of hydrogen ion increases in the human being blood, acidity boosts that outcomes weakness in body. In the condition, the body must keep alkaline by digesting food that produces alkali in the body, come neutralize the acidity.

Definitely, without acids or bases information, our stays would look various to how it watch now. Many assets we room using this day would have actually no use without this knowledge.


I am eternally grateful and also beholden to mine family. My mother Mrs. Suman Munjal, dad Mr. Bhim Sain Munjal and also sister Mrs. Shweta Java for strengthening me v the opportunities and also experiences which allowed me in reaching these heights. The reason behind this success is their selfless encouragement that assisted me explore brand-new dimensions in mine life.

I particularly acknowledge the donation of mine confidence Dr. Himanshu Mathur and also brother Mr. Chirag Munjal because that his continuous and constant support, effective efforts that proof reading my works, sort words of motivation, and providing me with helpful tips. I would favor to present my appreciation because that sharing his expertise and also experiences for organizing compelled resources.

Conflict of interest


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