Swedish Svante Arrhenius, in 1884 propose the ide of acid and also base based on the theory of ionization. Follow to Arrhenius, the acids room the hydrogen-containing compounds which give H+ ions or proton on dissociation in water and bases room the hydroxide compounds which offer OH− ion on dissociation in water. This ide is only applicable come those link which liquified in aqueous equipment (or you deserve to say where water is the solvent). It covers many typical acids, bases and their chemistry reactions, yet there are additionally other compounds that have actually the characteristics of acids and also bases yet they perform not fit right 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, institution of an easy Sciences, Jaipur national University, IndiaAakash Singh*Department the Chemistry, college of straightforward Sciences, Jaipur nationwide University, IndiaDepartment the Chemistry, Suditi an international Academy, India

*Address all correspondence to: aakashsingh.ucst

DOI: 10.5772/wgc2010.org.88173

From the Edited Volume


CorrosionEdited through Ambrish Singh

Edited through Ambrish Singh

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1. Introduction

The concept of acids and also bases have been characterized many time in different ways. Number of scientists placed various definitions to characterize the acids and bases in which few of the ideas are rather narrow and also some are comprehensive. Acids and bases room existing everywhere in our everyday life. Every liquid except water, that we used having actually acid and basic properties, for example, vinegar (contains acetic acid), soft drink (contains carbonic acid), buttermilk (contains lactic acid), soap (contains base). The earliest definitions were make on the communication of your taste and also their result on other substances.

1.1 Acids

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


1.2 factors affecting acidic strength

The strength of acids and bases depends on complying with 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 of the molecule increases, the electron thickness will get away from hydrogen atom and also it i do not care H+ (proton). The greater is the confident charge on the hydrogen atom, H▬A shortcut will end up being weaker, lesser is the energy required to break it. Then, the proton will easily dissociate in the solution. Hence, it will be the strong acid <1>.

* an essential points

The priority need to be offered to the polarity that H▬A bond, once we compare the acidic toughness of aspects in the same row. Yet when we compare the acidic strength of elements of same group of periodic table, climate priority is offered to strength of H▬A bond.

1.2.2 Electro negativity

The hydrogen is attach to the much more electronegative atom is more acidic. For instance - the hydrogen is attached come the oxygen (E.N=3.5) is more acidic than the hydrogen attached to nitrogen (E.N=3.0, i m sorry is less electronegative than oxygen).

1.2.3 Size

The dimension of “A” atom affects the acidity of acidic strength. As the dimension of the atom increases, the bond becomes weaker and acidic strength increases <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” character increases, therefore acidic stamin increases.

1.3 Bases

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

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

The Arrhenius acid-base theory was proposed by swedish Svante Arrhenius. It was the very first modern technique to acid-base concept. This theory is quite an easy and useful. Follow to Arrhenius theory, acids are the link that increases the concentration the H+ or proton in aqueous solution. The exit H+ ion or proton is not free-floating proton, it exist in an unified state through the water molecule and also forms hydronium ion (H3O+). The typical examples the 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 the is liquified in water, then:


The acids like HNO3, HCl, etc. Gives one proton top top dissociation, referred to as monoprotic acids. The acids prefer H2SO4, H3PO4, etc. I m sorry having an ext than one hydrogen atoms and gives an ext than 1 H+ ion on dissociation, dubbed polyprotic acids. That is not important that polyprotic acids room stronger than monoprotic acids.


Similarly, Arrhenius bases room compounds that boost the concentration of OH− or hydroxide ion in aqueous equipment or having at the very least one OH− ion in formula. The typical examples the Arrhenius base contains 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 sodium hydroxide liquified in water, it fully dissociates right into ions Na+ and OH−, this dissociation rises the concentration the 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 well-known 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 acid is a solid acid. When it dissociates into water, hydronium ion and also chloride ions are created as product. Chloride ions are weak base, however its basicity does not make the solution an easy because mountain is overpowering the basicity that chloride ions. The H+ ions integrate with water molecule and form hydronium ion. In situation of solid acid, the concentration that hydronium ion formed is equal to the concentration that the mountain whereas in instance of weak acids, the concentration that hydronium ion in systems is constantly less 보다 the concentration that hydrogen ions.

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

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

Similarly, bases which are totally ionized in aqueous solution, space termed as solid bases such together 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: the is not vital that strong acids/bases room concentrated and also weak acids/bases space dilute. Because, the dissociation the a problem does not depend on that is concentration.


3. Utility of Arrhenius concept

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


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

When electron is removing indigenous hydrogen atom, hydrogen ion H+ is developed which is very reactive. However this H+ ion does not exist in aqueous solution. Due to the fact that in aqueous medium, it reacts through water molecule and also forms hydronium ion (H3O+). Water is a polar molecule; it has actually the capability to tempt the hydrogen ion (H+). The water has hydrogen and also oxygen in which oxygen (EN=3.5) is an ext electronegative that pulls the electron density towards it and causing the partial an unfavorable charge ~ above the molecule. Because of partial an adverse charge, that has ability to attract the positively charged hydrogen ion (H+) and form hydronium ion (H3O+). Hydronium ions are much more stable 보다 hydrogen ions.

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


5. Concept of pH

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

pH=−log (H3O+)

From this equation, we can discover the pH the pure water. The pH the pure water involves be 7 the is considered to be neutral. The equipment is one of two people acidic or simple depending on the adjust in the concentration of hydronium ion.

According to figure 1:If the concentration that the hydronium ion in the equipment increases way more 보다 10−7mol/l, pH boosts that renders the solution more acidic.

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

Figure 1.

pH scale.


6. Amphoteric nature that water

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

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

According to Arrhenius acid-base theory:

The amphoteric nature that water is really important due to the fact that most of the acid-base chemistry reactions takes location in the presence of water. Water is crucial amphoteric link that have the right to act together both one Arrhenius acid or Arrhenius base.

Auto-ionization the water <4>;

The H+ ion (a ceiling proton) does no exist in the solution, it creates hydronium ion by hydrogen bonding v nearest water molecule. Many books refers the “concentration the hydrogen ions” i beg your pardon is not correct. Because there space no H+ ions, only hydronium ion in the solution. Technically, the number of hydronium ions developed is same to the variety of hydrogen ion. So, both deserve to be used.


7. Benefits of Arrhenius theory

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

The toughness of Arrhenius acid and also Arrhenius base can be figured out by the level to which it dissociate to give H+ ion or hydroxide ion <5>.The properties of acids and bases in aqueous medium.

Neutralization of mountain by reaction v base


8. Limitation of Arrhenius acid-base theory

This theory is really limited, out of 3 theories. Follow to this theory, the solution medium should it is in aqueous and also acid should produce hydrogen ion (H+) or base should develop hydroxide ion (OH−) ~ above dissociation through water. Hence, the problem is regarded as Arrhenius acid or Arrhenius base once it is dissolved in water. For example, HNO3 is pertained to as Arrhenius acid once it is dissolved in aqueous solution. Yet when the is liquified in any kind of other solvent favor benzene, no dissociation occurs. This is versus the Arrhenius theory.

Arrhenius concept is no applicable ~ above the non-aqueous or gas reactions because it explained the acid-base behavior in regards to aqueous solutions.

In Arrhenius theory, salt are produce in the product which are neither acidic no one basic. So, this theory cannot define the neutralization reaction without the existence of ions. Because that example, as soon as acetic acid (weak acid) and also sodium hydroxide (strong base) reacts, then the resulting equipment basic. However this concept is not explained by Arrhenius.

Arrhenius theory is only applicable come those compound which having actually formula HA or BOH because that acids and bases. There are some acids like AlCl3, CuSO4, CO2, SO2 which cannot be represented by HA formula, this concept is unable to describe their acidic behavior. Similarly, there are some bases choose Na2CO3, NH3, etc. Which perform not stood for by BOH formula, this concept is unable to define their an easy behavior.


9. Bronsted-Lowry theory

We have actually been previously learned one Arrhenius acid-base concept which detailed a an excellent start in the direction of the acid-base chemistry yet it has particular limitations and also problems. After this theory, a Danish chemist, called Johannes Nicolaus Bronsted and British scientist, cutting board Martin Lowry proposed a different definition 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, also called Proton theory of acid and base. This theory provides a more general and useful acid-base meaning and applies to wide range of chemistry reactions. In this theory, we usually think about a hydrogen atom as a proton that has actually lost that electrons and also becomes a positively charged hydrogen ion (represented by symbol, H+).

According come Bronsted-Lowry concept, an mountain is thought about to be Bronsted-Lowry mountain which is qualified to donate a proton to someone else. A base is considered to be Bronsted-Lowry base which is qualified to accept a proton from who else. Indigenous here, it have the right to note that as soon as an mountain reacts with 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 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 if the base is strong, the conjugate acid will be weak.

Consider the complying with chemical reaction:

In this reaction, HCl is an acid due to the fact that it is donating proton come NH3. Therefore, HCl is act as Bronsted-Lowry acid whereas NH3 has a lone pair of electron which is offered to expropriate 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 hydrogen chloride (HCl). In this case, the ammonium ion is donating a proton, referred to as conjugate acid. The chloride ion (Cl−) ion is accepting a proton, dubbed conjugate base.

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

Conjugate pair 2: NH3 and NH4+

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

Note: follow to the concept of Arrhenius, the reaction between HCl and NH3 is not thought about as acid-base reaction due to the fact that none that these varieties gives H+ and also OH− ions in water.

9.2 examples of Bronsted-Lowry acids and also bases

In this reaction, the nitric acid donates a proton to the water, because of this it act as a Bronsted-Lowry acid. Since, water accepts a proton indigenous nitric acid, so the is act as Bronsted-Lowry base. In this reaction, the arrowhead is attracted only come the appropriate side which method 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 the proton to the ammonia. Therefore, water is act as Bronsted-Lowry acid. Ammonia is agree a proton indigenous the water, develops ammonium ion (NH4+). Therefore, ammonia is act as Bronsted-Lowry base.

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

9.3 advantages of Bronsted-Lowry theory

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

It describes the simple character the substances favor NH3, CaO, Na2CO3, the is, which carry out not contain −OH group but according come Arrhenius theory, they room not taken into consideration as bases.

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

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

9.4 defect of Bronsted-Lowry theory

According come Bronsted-Lowry theory, very same compound is action as acid in one reaction and act as base in various other reaction. So, sometimes it is very difficult to guess the specific acid or basic in a reaction.

This theory is no able to define the acidic, an easy as well as Amphoteric gaseous molecule.

This concept does not explain the habits of acids prefer BF3, AlCl3, BCl3, etc. Which execute not protons to loosened or donate.

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


11. Lewis acid-base theory

The Bronsted-Lowry concept which we have actually been previously studied was a good startup for acid-base chemistry. The Bronsted-Lowry principle was based on the carry of proton indigenous one chemical types to another. Yet this concept has certain limitations. UC Berkeley scientist, G.N. Lewis, in 1923 propose a new acid-base concept which is based on their deliver of electrons. This theory is much more advanced and also flexible 보다 Bronsted-Lowry since it describes the acid-base behavior in that molecules which execute 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 expropriate the non-bonding pair that electrons, called Lewis acid. They are periodically referred together electron deficient species or electrophile.

11.1.1 Lewis acid: characteristics

Lewis acid-electron-pair acceptor.

Lewis mountain should have 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 however all Lewis acids room not cations.

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

For example: BF3.

Here, you deserve to see the the central atom boron has actually six electrons in its outermost shell. So, that has ability to accept much more electrons due to the existence of an north orbital and hence, act together Lewis acid.

The molecule in i m sorry the central atom has more than eight electron (SiF4, SiBr4), are likewise considered together Lewis acids.

The molecule prefer CO2, SO2, etc. Are additionally considered as Lewis acid. These varieties of molecules form multiple bond in between the atoms of different electronegativity. In instance of shift metal ions, the steel having an ext electronegativity provides stronger Lewis acids.

Electron bad п: system 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. They are sometimes referred as electron rich types or Nucleophile.

11.2.1 Lewis base: characteristics

Lewis base-electron-pair donor

All metal anions (F−, Cl−, Br−, I−) room Lewis base because they have capacity to donate the electron however all Lewis bases are not anions.

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

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

The strength of the Lewis base can be raised by boosting the electron density.

Note: as soon as a Lewis acid reacts with Lewis base, climate Lewis acid supplies its shortest unoccupied molecular orbital (LUMO) and also base offers its highest possible occupied molecular orbital (HUMO) to create a external inspection 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 always considered together acid.

11.4 Neutralization reaction between Lewis acid and also Lewis base

When a Lewis mountain reacts with a Lewis base, climate a Lewis acid-base reaction occurs in i beg your pardon the molecule i m sorry act together Lewis basic donate the electron pair into the north orbital of one acid, develops Lewis acid-base adduct as presented in number 2. The adduct formed includes 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 also Lewis base is a high electron density centre <6>.

Figure 2.

Acid-base neutralization.

In this reaction, the 2 ammonia molecule reacts with silver ion. The ammonia has lone pair that electrons, therefore it has the capacity to donate the lone pairs of electrons and acts as Lewis base. The optimistic charge on silver- denotes that is electrophilic nature that method it has actually an capability to accept the bag of electrons and also act as Lewis acid (by Lewis definition).

Here, the can likewise be provided that when a Lewis acid reacts through a Lewis base, over there is no adjust in the oxidation variety of any of these atoms.

11.5 limitations of Lewis acid-base theory

This theory is no able to describe that why every acid-base reactions carry out not involve the covalent coordination bond.

This theory is additionally unable to define the behavior of part acids favor hydrogen chloride (HCl) and also sulfuric acid (H2SO4) because they perform not kind the covalent coordination bond through bases. Hence, they room not considered as Lewis acids.

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

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

This theory stops working to define the catalytic task of part Lewis acids.

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

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

13. Conclusion

Acids and bases are very important for contemporary society and in our day-to-day lives. Castle exist almost everywhere in ours body and also in ours surroundings. The concept that has been explained in this chapter has provided us every the simple information of acids and bases. In this chapter, we have disputed all the three straightforward theory that acid-base chemistry-Arrhenius theory, Bronsted-Lowry theory and Lewis acid-base theory. Acids and bases have vital role in the area that medicine. Native this concept, it is currently easy to treat the diseases with the improved medicines by complicated understanding that acids and also bases. For example, If the concentration of hydrogen ion increases in the person blood, acidity boosts that results weakness in body. In that condition, the body must keep alkaline by digesting food the produces alkali in the body, to neutralize the acidity.

Definitely, without acids or bases information, our resides would look different to exactly how it looks now. Many commodities we space using today would have no usage without this knowledge.


I to be eternally grateful and beholden to my family. My mom Mrs. Suman Munjal, dad Mr. Bhim Sain Munjal and sister Mrs. Shweta Java because that strengthening me through the opportunities and experiences which enabled me in getting to these heights. The reason behind this success is their selfless encourage that aided me explore new dimensions in my life.

I particularly acknowledge the contribution of my confidence Dr. Himanshu Mathur and also brother Mr. Chirag Munjal for his continuous and consistent support, effective efforts the proof reading my works, type words that motivation, and also providing me with advantageous tips. Ns would choose to display my appreciation for sharing his expertise and experiences for organizing required resources.

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