Swedish Svante Arrhenius, in 1884 proposed the principle of acid and base based upon the concept of ionization. Follow to Arrhenius, the acids space the hydrogen-containing link which provide H+ ion or proton on dissociation in water and also bases are the hydroxide compounds which provide OH− ion on dissociation in water. This concept is only applicable come those link which dissolved in aqueous equipment (or you can say where water is the solvent). The covers many typical acids, bases and their chemistry reactions, but there are likewise other compound that have the features of acids and also bases yet they do not fit into Arrhenius concept.

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

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Shikha MunjalDepartment that Chemistry, school of basic 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/ubraintv-jp.com.88173

From the Edited Volume


CorrosionEdited by Ambrish Singh

Edited through Ambrish Singh

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1. Introduction

The ide of acids and bases have been characterized many time in different ways. Several scientists put various meanings to characterize the acids and bases in which several of the concepts are fairly narrow and also some are comprehensive. Acids and also bases space existing almost everywhere in our everyday life. Every liquid except water, that us used having actually acid and simple properties, for example, vinegar (contains acetic acid), soft drink (contains carbonic acid), buttermilk (contains lactic acid), soap (contains base). The earliest interpretations were made on the basis of your taste and their impact on various other substances.

1.1 Acids

Acid space those substances which have sour in taste, spicy odor, corrosive, having pH2. For example, the reaction between sodium hydroxide (base) and also hydrochloric acid, creates sodium chloride (salt) and also water.


1.2 factors affecting acidic strength

The strength of acids and bases depends on adhering to factors:Polarity of the molecule and strength the H▬A bond

Electro negativity


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

As the polarity the the molecule increases, the electron density will gain away indigenous hydrogen atom and also it becomes H+ (proton). The better is the positive charge top top the hydrogen atom, H▬A shortcut will end up being weaker, lesser is the power required to rest it. Then, the proton will conveniently dissociate in the solution. Hence, it will be the solid acid <1>.

* key points

The priority need to be given to the polarity that H▬A bond, when we compare the acidic stamin of elements in the exact same row. However when us compare the acidic stamin of facets of same team of periodic table, climate priority is given to strength 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 come the oxygen (E.N=3.5) is an ext acidic 보다 the hydrogen attached come nitrogen (E.N=3.0, which is much less electronegative 보다 oxygen).

1.2.3 Size

The size of “A” atom affects the acidity of acidic strength. Together the size of the atom increases, the bond i do not care weaker and acidic strength boosts <2>.

1.2.4 Hybridization

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

1.3 Bases

Bases are those building material which have bitter taste, odorless, revolve red litmus blue, having actually pH an ext than 7 and becomes less alkaline as soon as react v acid. These space violent and also less reactive than acids. Because that 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 space some crucial 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 theory was suggest by swedish Svante Arrhenius. It to be the first modern method to acid-base concept. This concept is quite simple and useful. According to Arrhenius theory, acids room the compound that rises the concentration of H+ or proton in aqueous solution. The released H+ ion or proton is not free-floating proton, it exist in merged state through the water molecule and forms hydronium ion (H3O+). The typical 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 it is liquified in water, then:


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


Similarly, Arrhenius bases space compounds that increase the concentration of OH− or hydroxide ion in aqueous solution or having actually at the very least one OH− ion in formula. The usual examples that Arrhenius base contains 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 salt hydroxide dissolved in water, it completely dissociates into ions Na+ and also OH−, this dissociation boosts the concentration that hydroxide ions in the solution.

2.1 Neutralization reaction

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

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

Hydrochloric acid is a solid acid. Once it dissociates right into water, hydronium ion and also chloride ions are created as product. Chloride ions room weak base, however its basicity does no make the solution simple because acidity is overpowering the basicity the chloride ions. The H+ ions combine with water molecule and kind hydronium ion. In case of strong acid, the concentration that hydronium ion created is equal to the concentration that the mountain whereas in situation of weak acids, the concentration of hydronium ion in equipment is constantly less 보다 the concentration that hydrogen ions.

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

In case of weak acids, the concentration the hydronium ion is constantly less than the concentration that acid.

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

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

3. Energy of Arrhenius concept

This concept explains countless phenomena prefer strength the acids and also bases, salt hydrolysis and neutralization.

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

When electron is removing native hydrogen atom, hydrogen ion H+ is formed which is an extremely reactive. However this H+ ion does not exist in aqueous solution. Because in aqueous medium, it reacts through water molecule and also forms hydronium ion (H3O+). Water is a polar molecule; it has the capability to tempt the hydrogen ion (H+). The water contains hydrogen and also 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. As result of partial negative charge, it has capability to attract the positively charged hydrogen ion (H+) and kind hydronium ion (H3O+). Hydronium ions are much more stable 보다 hydrogen ions.

The hydronium ion is really important factor in chemical reaction that occurs in aqueous solutions <3>. The is formed by the protonation the water.

5. Principle of pH

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

pH=−log (H3O+)

From this equation, us can find the pH that pure water. The pH of pure water involves be 7 the is considered to be neutral. The systems is one of two people acidic or straightforward depending on the readjust in the concentration that hydronium ion.

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

If the concentration that the hydronium ion in the systems decreases means −7mol/l, pH to reduce that provides the solution more basic.

Figure 1.

pH scale.


6. Amphoteric nature the water

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

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

According to Arrhenius acid-base theory:

The amphoteric nature the water is very important since most that the acid-base chemistry reactions takes location in the presence of water. Water is important amphoteric compound that can act together both an Arrhenius mountain or Arrhenius base.

Auto-ionization of water <4>;

The H+ ion (a ceiling proton) does not exist in the solution, it develops hydronium ions by hydrogen bonding v nearest water molecule. Many books refers the “concentration that hydrogen ions” which is not correct. Due to the fact that there are 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 have the right to be used.

7. Benefits of Arrhenius theory

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

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

Neutralization of mountain by reaction with base

8. Limitation of Arrhenius acid-base theory

This theory is an extremely limited, out of 3 theories. According to this theory, the solution medium should it is in aqueous and acid should produce hydrogen ion (H+) or base should develop hydroxide ion (OH−) ~ above dissociation with water. Hence, the problem is pertained to as Arrhenius acid or Arrhenius base as soon as it is dissolved in water. Because that example, HNO3 is concerned as Arrhenius acid as soon as it is liquified in aqueous solution. However when that is dissolved in any other solvent favor benzene, no dissociation occurs. This is versus the Arrhenius theory.

Arrhenius concept is not applicable on the non-aqueous or gas reactions since it defined the acid-base habits in regards to aqueous solutions.

In Arrhenius theory, salt are create in the product which room neither acidic nor basic. So, this concept cannot explain the neutralization reaction without the presence of ions. For example, when acetic acid (weak acid) and sodium hydroxide (strong base) reacts, climate the resulting equipment basic. However this concept is not described by Arrhenius.

Arrhenius concept is only applicable come those compound which having formula HA or BOH for acids and bases. There room some acids prefer AlCl3, CuSO4, CO2, SO2 which can not be stood for by HA formula, this theory is can not to explain their acidic behavior. Similarly, there are some bases prefer Na2CO3, NH3, etc. Which carry out not represented by BOH formula, this theory is unable to describe their simple 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 specific limitations and also problems. ~ this theory, a Danish chemist, called Johannes Nicolaus Bronsted and British scientist, thomas Martin Lowry suggest a different an interpretation of acid-base that based on the abilities of compound to either donate or expropriate the protons. This concept is known as Bronsted-Lowry theory, likewise called Proton concept of acid and also base. This theory offers a much more general and also useful acid-base an interpretation and applies to wide selection of chemistry reactions. In this theory, we usually think about a hydrogen atom together a proton that has lost the electrons and becomes a positively charged hydrogen ion (represented by symbol, H+).

According come Bronsted-Lowry concept, an acid is taken into consideration to be Bronsted-Lowry acid which is qualified to donate a proton to who else. A base is taken into consideration to it is in Bronsted-Lowry basic which is capable to expropriate a proton from someone else. From here, it can note that once an mountain reacts with a base, the proton is transferred 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 base accepts proton.

Conjugate base: It forms 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 an acid because it is donating proton come NH3. Therefore, HCl is act together Bronsted-Lowry mountain whereas NH3 has a lone pair of electron which is provided to expropriate 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 also hydrogen chloride (HCl). In this case, the ammonium ion is donating a proton, dubbed conjugate acid. The chloride ion (Cl−) ion is agree a proton, called 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 the equation, the ammonium ion (NH4+) is a conjugate acid of base ammonia and chloride ion (Cl−) is a conjugate basic of mountain hydrogen chloride.

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

9.2 examples of Bronsted-Lowry acids and also bases

In this reaction, the nitric acid donates a proton to the water, as such it act together a Bronsted-Lowry acid. Since, water accepts a proton from nitric acid, so it is act together Bronsted-Lowry base. In this reaction, the arrowhead is attracted only come the best side which way that reaction extremely favours the formation of products.

In this reaction, the water is losing its proton, becomes hydroxide (OH−) and also donates the proton to the ammonia. Therefore, water is act as Bronsted-Lowry acid. Ammonia is accepting a proton from the water, creates ammonium ion (NH4+). Therefore, ammonia is act together Bronsted-Lowry base.

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

9.3 benefits of Bronsted-Lowry theory

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

It explains the basic character of substances prefer NH3, CaO, Na2CO3, that is, which perform not save −OH group yet according to Arrhenius theory, they are not thought about as bases.

It defines the acidic character of substances favor CO2, SO2, etc. Which do not save hydrogen ion group however according come Arrhenius theory, they space not thought about as acids.

This theory also explains the acid-base habits of ionic species.

9.4 disadvantages of Bronsted-Lowry theory

According to Bronsted-Lowry theory, very same compound is act as mountain in one reaction and act together base in various other reaction. So, sometimes it is very difficult to suspect the exact acid or basic in a reaction.

This concept is not able to explain the acidic, an easy as well together Amphoteric gas molecule.

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

This concept does not define reactions between acidic oxides (CO2, SO2, SO3) and straightforward oxides (CaO, MgO, BrO) i beg your pardon takes ar in the absence of solvent.


11. Lewis acid-base theory

The Bronsted-Lowry theory which we have been formerly studied to be a great startup for acid-base chemistry. The Bronsted-Lowry ide was based on the transfer of proton from one chemical types to another. However this theory has particular limitations. UC Berkeley scientist, G.N. Lewis, in 1923 suggest a new acid-base theory which is based upon their move of electrons. This concept is much more advanced and also flexible than Bronsted-Lowry since it describes the acid-base actions in the molecules which do not save on computer hydrogen ions or in non-aqueous medium.

11.1 Lewis acid

According come this theory, an mountain is a substance which has ability to accept the non-bonding pair that electrons, called Lewis acid. Lock are occasionally referred as electron deficient types or electrophile.

11.1.1 Lewis acid: characteristics

Lewis acid-electron-pair acceptor.

Lewis mountain should have actually a vacant or north orbital.

All cations (Na+, Cu2+, Fe3+) space Lewis acids since they have capacity to expropriate a pair the electrons however all Lewis acids are not cations.

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

For example: BF3.

Here, you have the right to see the the main atom boron has six electron in the outermost shell. So, that has capability to accept an ext electrons because of the visibility of an north orbital and hence, act as Lewis acid.

The molecule in which the main atom has much more than eight electron (SiF4, SiBr4), are additionally considered as Lewis acids.

The molecule favor CO2, SO2, etc. Are additionally considered together Lewis acid. These types of molecules form multiple bond in between the atom of various electronegativity. In case of shift metal ions, the steel having an ext electronegativity renders stronger Lewis acids.

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

11.2 Lewis base

A base is a problem which has capacity to donate the electrons, called Lewis base. Castle are sometimes 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−) room Lewis base since they have capacity to donate the electron yet all Lewis bases room not anions.

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

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

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

Note: once a Lewis acid reacts v Lewis base, then Lewis acid uses its lowest unoccupied molecular orbital (LUMO) and also base uses its greatest occupied molecular orbital (HUMO) to produce a external inspection molecular orbital. Actually, Lewis acid and also Lewis basic both have LUMO and also HUMO but HUMO is constantly considered as base and also LUMO is always considered as acid.

11.4 Neutralization reaction in between Lewis acid and Lewis base

When a Lewis mountain reacts through a Lewis base, climate a Lewis acid-base reaction occurs in i beg your pardon the molecule i beg your pardon act as Lewis basic donate that is electron pair right into the north orbital of an acid, develops Lewis acid-base adduct as presented in figure 2. The adduct formed has a covalent name: coordinates bond between Lewis acid and also Lewis base. The over explanation means that the Lewis acid is a short electron thickness centre and Lewis base is a high electron thickness centre <6>.

Figure 2.

Acid-base neutralization.

In this reaction, the two ammonia molecules reacts through silver ion. The ammonia has lone pair of electrons, for this reason it has the ability to donate the lone bag of electrons and also acts together Lewis base. The hopeful charge on silver- denotes the electrophilic nature that means it has actually an ability to accept the bag of electrons and also act together Lewis mountain (by Lewis definition).

Here, it can also be noted that when a Lewis acid reacts v 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 carry out not involve the covalent coordination bond.

This theory is also unable to explain the behavior of some acids favor hydrogen chloride (HCl) and also sulfuric acid (H2SO4) since they execute not type the covalent coordination bond through bases. Hence, they room not thought about as Lewis acids.

This concept cannot define the principle that why the formation of coordination link is a slow process and acid-base reaction is a quick process.

This theory cannot explain the concept of relative strength that acids and also bases.

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

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

All Arrhenius acids and also Bronsted Lowry acids space Lewis acids however reverse is not true.

13. Conclusion

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

Definitely, without acids or bases information, our lives would look various to how it looks now. Many assets we are using this day would have no use without this knowledge.


I am eternally grateful and also beholden to mine family. My mom Mrs. Suman Munjal, dad Mr. Bhim Sain Munjal and also sister Mrs. Shweta Java for strengthening me v the opportunities and also experiences which permitted me in getting to these heights. The reason behind this success is your selfless encouragement that assisted me explore 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 constant and continual support, efficient efforts the proof reading my works, sort words of motivation, and providing me with valuable tips. Ns would like to present my appreciation for sharing his expertise and experiences for organizing forced resources.

Conflict of interest


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