Swedish Svante Arrhenius, in 1884 suggest the ide of acid and base based on the theory of ionization. Follow to Arrhenius, the acids are the hydrogen-containing compound which provide H+ ion or protons on dissociation in water and also bases space the hydroxide compound which offer OH− ions on dissociation in water. This concept is only applicable come those link which liquified in aqueous solution (or you have the right to say where water is the solvent). That covers many common acids, bases and also their chemistry reactions, however there are also other compound that have the features of acids and also bases however they execute not fit right into Arrhenius concept.

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Shikha MunjalDepartment that Chemistry, school of simple Sciences, Jaipur nationwide University, IndiaAakash Singh*Department the Chemistry, college of an easy Sciences, Jaipur nationwide University, IndiaDepartment the Chemistry, Suditi global Academy, India

*Address every correspondence to: aakashsingh.ucst

DOI: 10.5772/chathamtownfc.net.88173

From the Edited Volume


CorrosionEdited through Ambrish Singh

Edited by Ambrish Singh

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1. Introduction

The ide of acids and bases have been characterized many times in different ways. Number of scientists placed various definitions to characterize the acids and bases in which some of the concepts are rather narrow and also some are comprehensive. Acids and bases are existing all over in our day-to-day life. Every liquid except water, that us used having acid and an easy properties, for example, vinegar (contains acetic acid), soft drinks (contains carbonic acid), buttermilk (contains lactic acid), soap (contains base). The earliest definitions were do on the basis of their taste and also their impact on various other substances.

1.1 Acids

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


1.2 factors affecting acidic strength

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

Electro negativity


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

As the polarity the the molecule increases, the electron thickness will gain away native hydrogen atom and it becomes H+ (proton). The better is the optimistic charge top top the hydrogen atom, H▬A link will become weaker, lesser is the energy required to rest it. Then, the proton will conveniently dissociate in the solution. Hence, it will certainly be the solid acid <1>.

* vital points

The priority should be provided to the polarity the H▬A bond, as soon as we to compare the acidic toughness of elements in the exact same row. However when us compare the acidic toughness of elements of same team of periodic table, then priority is given to stamin of H▬A bond.

1.2.2 Electro negativity

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

1.2.3 Size

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

1.2.4 Hybridization

Hybridization plays critical role in determining the acidic strength. Together the hybridization moves from sp3 to sp, the “s” personality increases, so acidic toughness increases.

1.3 Bases

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

These space the general properties of mountain or bases, but not true because that every solitary acid or base. There space some essential 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 suggest by sweden Svante Arrhenius. It to be the an initial modern technique to acid-base concept. This concept is quite simple and useful. According to Arrhenius theory, acids are the link that boosts the concentration the H+ or proton in aqueous solution. The released H+ ion or proton is no free-floating proton, it exists in linked state through the water molecule and also forms hydronium ion (H3O+). The common examples that Arrhenius acid contains HCl (hydrochloric acid), H2SO4 (sulphuric acid), HNO3 (nitric acid), etc. As presented in Table 1.


Arrhenius mountain 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. Gives one proton ~ above dissociation, called monoprotic acids. The acids prefer H2SO4, H3PO4, etc. I beg your pardon having an ext than one hydrogen atoms and also gives more than 1 H+ ion on dissociation, dubbed polyprotic acids. That is not crucial that polyprotic acids space stronger 보다 monoprotic acids.


Similarly, Arrhenius bases are compounds that rise the concentration that OH− or hydroxide ion in aqueous solution or having at least one OH− ion in formula. The common examples that 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 presented 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 fully dissociates right into ions Na+ and OH−, this dissociation increases the concentration that hydroxide ions in the solution.

2.1 Neutralization reaction

When Arrhenius acid and Arrhenius basic reacts, salt and water is developed as product, the reaction is known as neutralization reaction. For example:

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

Hydrochloric acid is a strong acid. As soon as it dissociates into water, hydronium ion and also chloride ion are developed as product. Chloride ions space weak base, yet its basicity does not make the solution an easy because mountain is overpowering the basicity of chloride ions. The H+ ions integrate with water molecule and type hydronium ion. In instance of solid acid, the concentration the hydronium ion developed is equal to the concentration that the acid whereas in instance of weak acids, the concentration of hydronium ion in equipment is constantly less than the concentration of hydrogen ions.

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

In situation of weak acids, the concentration of hydronium ion is constantly less 보다 the concentration that acid.

Similarly, bases i beg your pardon are totally ionized in aqueous solution, room termed as solid bases such as NaOH, KOH, etc. Vice versa, 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: it is not essential that solid acids/bases space concentrated and weak acids/bases are dilute. Because, the dissociation of a problem does not rely on the concentration.


3. Utility of Arrhenius concept

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


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

When electron is removing indigenous hydrogen atom, hydrogen ion H+ is formed which is very reactive. However this H+ ion does not exist in aqueous solution. Due to the fact that in aqueous medium, that reacts with water molecule and forms hydronium ion (H3O+). Water is a polar molecule; it has actually the capacity to tempt the hydrogen ion (H+). The water has hydrogen and also oxygen in which oxygen (EN=3.5) is much more electronegative the pulls the electron thickness towards it and causing the partial an adverse charge top top the molecule. Due to partial an unfavorable charge, the has capability to lure the positively fee hydrogen ion (H+) and form hydronium ion (H3O+). Hydronium ion are much more stable than hydrogen ions.

The hydronium ion is very important aspect in chemical reaction the occurs in aqueous remedies <3>. It is created by the protonation the water.


5. Ide of pH

The pH of solution have the right to be identified by the concentration of hydronium ion.

pH=−log (H3O+)

From this equation, us can uncover the pH the pure water. The pH the pure water involves be 7 the is thought about to it is in neutral. The solution is one of two people acidic or an easy depending ~ above the readjust in the concentration that hydronium ion.

According to number 1:If the concentration of the hydronium ion in the solution increases method more 보다 10−7mol/l, pH boosts that renders the solution an ext acidic.

If the concentration of the hydronium ion in the systems decreases method −7mol/l, pH reduce that renders the solution an ext basic.

Figure 1.

pH scale.


6. Amphoteric nature that water

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

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

According to Arrhenius acid-base theory:

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

Auto-ionization that water <4>;

The H+ ion (a bare proton) does no exist in the solution, it forms hydronium ions by hydrogen bonding with nearest water molecule. Many publications refers the “concentration of hydrogen ions” i beg your pardon is no correct. Because there room no H+ ions, just hydronium ions in the solution. Technically, the number of hydronium ions developed is equal to the variety of hydrogen ion. So, both can be used.


7. Advantages of Arrhenius theory

This theory is supplied to explains:Strength the acid and bases

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

Neutralization of mountain by reaction through base


8. Limitation of Arrhenius acid-base theory

This theory is very limited, the end of three theories. According to this theory, the solution tool 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 concerned as Arrhenius acid or Arrhenius base when it is dissolved in water. For example, HNO3 is concerned as Arrhenius acid once it is liquified in aqueous solution. Yet when it is liquified in any type of other solvent like benzene, no dissociation occurs. This is against the Arrhenius theory.

Arrhenius concept is no applicable top top the non-aqueous or gaseous reactions since it described the acid-base behavior in terms of aqueous solutions.

In Arrhenius theory, salts are create in the product which room neither acidic nor basic. So, this concept cannot describe the neutralization reaction there is no the visibility of ions. For example, when acetic mountain (weak acid) and also sodium hydroxide (strong base) reacts, climate the resulting systems basic. Yet this concept is not defined by Arrhenius.

Arrhenius concept is just applicable to those compound which having formula HA or BOH for acids and bases. There space some acids prefer AlCl3, CuSO4, CO2, SO2 which can not be stood for by HA formula, this theory is unable to define their acidic behavior. Similarly, there space some bases choose Na2CO3, NH3, etc. Which do not stood for by BOH formula, this theory is can not to describe their an easy behavior.


9. Bronsted-Lowry theory

We have been previously learned an Arrhenius acid-base concept which noted a great start in the direction of the acid-base chemistry however it has certain limitations and also problems. ~ this theory, a Danish chemist, called Johannes Nicolaus Bronsted and British scientist, thomas Martin Lowry suggest a different meaning 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, additionally called Proton concept of acid and also base. This theory provides a more general and also useful acid-base meaning and uses to wide variety of chemistry reactions. In this theory, we usually consider a hydrogen atom together a proton that has actually lost its electrons and also becomes a positively fee hydrogen ion (represented through symbol, H+).

According to Bronsted-Lowry concept, an acid is thought about to it is in Bronsted-Lowry mountain which is capable to donate a proton to who else. A basic is considered to be Bronsted-Lowry base which is capable to accept a proton from who else. Indigenous here, it have the right to note that when an acid reacts through a base, the proton is moved from one chemical species 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 creates when a basic accepts proton.

Conjugate base: It creates when an mountain donates proton.

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

Consider the adhering to chemical reaction:

In this reaction, HCl is one acid because it is donating proton come NH3. Therefore, HCl is act together Bronsted-Lowry acid whereas NH3 has a lone pair of electron which is used to accept the protons. Therefore, NH3 is act as Bronsted-Lowry base. This reaction is reversible also. In reversible case, the ammonium ion reacts with chloride ion and also again converts 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 agree a proton, dubbed conjugate base.

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

Conjugate pair 2: NH3 and also NH4+

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

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

9.2 examples of Bronsted-Lowry acids and bases

In this reaction, the nitric acid donates a proton to the water, as such it act as a Bronsted-Lowry acid. Since, water accepts a proton native nitric acid, so that is act together Bronsted-Lowry base. In this reaction, the arrow is drawn only come the best side which method that reaction extremely favours the development of products.

In this reaction, the water is shedding its proton, becomes hydroxide (OH−) and donates the proton come the ammonia. Therefore, water is act together Bronsted-Lowry acid. Ammonia is accepting a proton indigenous the water, develops ammonium ion (NH4+). Therefore, ammonia is act as Bronsted-Lowry base.

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

9.3 advantages of Bronsted-Lowry theory

This concept is able to describe the acid-base habits in aqueous and non-aqueous medium.

It explains the an easy character that substances choose NH3, CaO, Na2CO3, the is, which do not contain −OH group yet according come Arrhenius theory, they space not thought about as bases.

It describes the acidic character of substances choose CO2, SO2, etc. Which execute not save hydrogen ion group but according to Arrhenius theory, they are not taken into consideration as acids.

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

9.4 disadvantages of Bronsted-Lowry theory

According come Bronsted-Lowry theory, exact same compound is plot as mountain in one reaction and act as base in other reaction. So, periodically it is very daunting to guess the specific acid or basic in a reaction.

This theory is no able to explain the acidic, simple as well as Amphoteric gaseous molecule.

This theory does not define the habits of acids prefer BF3, AlCl3, BCl3, etc. Which do not protons to loose or donate.

This theory does not describe reactions in 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 actually been previously studied to be a an excellent startup for acid-base chemistry. The Bronsted-Lowry ide was based upon the deliver of proton native one chemical types to another. However this theory has details limitations. UC Berkeley scientist, G.N. Lewis, in 1923 suggest a brand-new acid-base concept which is based upon their transfer of electrons. This theory is much more advanced and also flexible than Bronsted-Lowry due to the fact that it describes the acid-base actions in the molecules which perform not save hydrogen ion or in non-aqueous medium.

11.1 Lewis acid

According come this theory, an mountain is a substance which has capacity to expropriate the non-bonding pair the electrons, dubbed Lewis acid. Lock are occasionally referred together electron deficient species or electrophile.

11.1.1 Lewis acid: characteristics

Lewis acid-electron-pair acceptor.

Lewis acid should have actually a vacant or empty orbital.

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

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

For example: BF3.

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

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

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

Electron bad п: system is additionally considered as Lewis acids, because that example, +, etc.

11.2 Lewis base

A basic is a problem which has capability to donate the electrons, called Lewis base. They are periodically referred together electron rich species 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 capability to donate the electron but all Lewis bases are not anions.

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

The electron-rich п system is likewise considered together Lewis bases, because that example, benzene, ethene, etc.

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

Note: when a Lewis mountain reacts with Lewis base, climate Lewis acid uses its lowest unoccupied molecular orbit (LUMO) and also base uses its highest possible occupied molecular orbital (HUMO) to develop a external inspection molecular orbital. Actually, Lewis acid and Lewis base both have LUMO and HUMO yet HUMO is always considered as base and LUMO is always considered as acid.

11.4 Neutralization reaction in between Lewis acid and also Lewis base

When a Lewis mountain reacts with a Lewis base, climate a Lewis acid-base reaction wake up in which the molecule i beg your pardon act together Lewis base donate that is electron pair right into the empty orbital of an acid, forms Lewis acid-base adduct as presented in number 2. The adduct formed has a covalent coordinate bond in between Lewis acid and Lewis base. The above explanation means that the Lewis acid is a low electron density centre and Lewis basic is a high electron density centre <6>.

Figure 2.

Acid-base neutralization.

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

Here, it can additionally be listed that when a Lewis acid reacts with 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 not able to describe that why all acid-base reactions perform not show off the covalent coordination bond.

This theory is also unable to describe the actions of some acids prefer hydrogen chloride (HCl) and sulfuric acid (H2SO4) because they carry out not form the covalent coordination bond with bases. Hence, they room not taken into consideration as Lewis acids.

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

This theory cannot describe the ide of loved one strength the acids and bases.

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

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

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

13. Conclusion

Acids and bases are really important for contemporary society and also in our day-to-day lives. They exist almost everywhere in ours body and also in our surroundings. The theory that has actually been explained in this chapter has provided us all the simple information that acids and bases. In this chapter, we have discussed all the three basic theory that acid-base chemistry-Arrhenius theory, Bronsted-Lowry theory and Lewis acid-base theory. Acids and bases have an important role in the area the medicine. Indigenous this concept, it is now easy come treat the illness with the boosted medicines by complicated understanding of acids and also bases. For example, If the concentration of hydrogen ion increases in the human blood, acidity rises that outcomes weakness in body. In that condition, the body need to keep alkaline by digesting food the produces alkali in the body, come neutralize the acidity.

Definitely, without mountain or bases information, our stays would look various to just how it watch now. Many assets we room using now would have no usage without this knowledge.


I am eternally grateful and beholden to mine family. My mother Mrs. Suman Munjal, father Mr. Bhim Sain Munjal and sister Mrs. Shweta Java because that strengthening me v the opportunities and experiences which enabled me in reaching these heights. The factor behind this success is their selfless encouragement that assisted 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 because that his consistent and regular support, efficient efforts the proof analysis my works, kind words of motivation, and providing me with valuable tips. I would choose to show my appreciation because that sharing his expertise and experiences because that organizing compelled resources.

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