Note: If an acid is strong, the conjugate base will be weaker and if the base is strong, the conjugate acid will be weak. In this reaction, HCl is an acid because it is donating proton to NH 3. Therefore, HCl is act as Bronsted-Lowry acid whereas NH 3 has a lone pair of electrons which is used to accept the protons. Therefore, NH 3 is act as Bronsted-Lowry base. This reaction is reversible also.
In reversible case, the ammonium ion reacts with chloride ion and again converts into ammonia NH 3 and hydrogen chloride HCl. In this case, the ammonium ion is donating a proton, called conjugate acid.
There are two conjugate pairs—conjugate pair 1 and conjugate pair 2. In this reaction, the nitric acid donates a proton to the water, therefore it act as a Bronsted-Lowry acid. Since, water accepts a proton from nitric acid, so it is act as Bronsted-Lowry base. In this reaction, the arrow is drawn only to the right side which means that reaction highly favours the formation of products. Therefore, water is act as Bronsted-Lowry acid. Therefore, ammonia is act as Bronsted-Lowry base. From the above two reactions, we can conclude that the water is Amphoteric in nature which means that it can act as both: Bronsted-Lowry acid and Bronsted-Lowry base.
This theory is able to explain the acid-base behavior in aqueous and non-aqueous medium. It explains the acidic character of substances like CO 2 , SO 2 , etc. According to Bronsted-Lowry theory, same compound is act as acid in one reaction and act as base in other reaction. So, sometimes it is very difficult to predict the exact acid or base in a reaction. This theory is not able to explain the acidic, basic as well as Amphoteric gaseous molecule.
These two theories are not against to each other in any way, in fact Bronsted-Lowry theory is advance to the Arrhenius theory. According to the Arrhenius theory, a substance which produces hydrogen ion in water, called acid. A substance which produces hydroxide ion in water, called base.
According to Bronsted-Lowry theory, an acid is proton donor and base is proton acceptor. According to Arrhenius theory, hydrochloric acid is an acid which gives hydrogen ions in water but according to Bronsted-Lowry theory, hydrochloric acid is an acid because it donates a proton to the water molecule. By observing both concepts, water is acting as a base. So, we can see here that both theories are very similar to each other.
Actually, Arrhenius theory is limited only to the aqueous solution. It does not explain the acid behavior in gaseous form. The Bronsted-Lowry theory which we have been previously studied was a good startup for acid-base chemistry. The Bronsted-Lowry concept was based on the transfer of proton from one chemical species to another. But this theory has certain limitations. UC Berkeley scientist, G.
Lewis, in proposed a new acid-base theory which is based on their transfer of electrons. This theory is more advanced and flexible than Bronsted-Lowry because it explains the acid-base behavior in that molecules which do not contain hydrogen ions or in non-aqueous medium. According to this theory, an acid is a substance which has capability to accept the non-bonding pair of electrons, called Lewis acid.
They are sometimes referred as electron deficient species or electrophile. More is the positive charge on the metal, more is the acidic character. The ion, molecule or an atom which has incomplete octet of electrons are also Lewis acids. Here, you can see that the central atom boron has six electrons in its outermost shell. So, it has ability to accept more electrons due to the presence of an empty orbital and hence, act as Lewis acid. The molecule in which the central atom has more than eight electrons SiF 4 , SiBr 4 , are also considered as Lewis acids.
The molecule like CO 2 , SO 2 , etc. These types of molecules form multiple bond between the atoms of different electronegativity. In case of transition metal ions, the metal having more electronegativity makes stronger Lewis acids.
A base is a substance which has capability to donate the electrons, called Lewis base. They are sometimes referred as electron rich species or Nucleophile. The ion, molecule or an atom which having a lone pair of electrons, are also considered as Lewis base. In this reaction, chloride ion acts as Lewis base because it has lone pairs of electrons and sodium ion has positive charge, so it acts as Lewis acid. When a Lewis acid reacts with a Lewis base, then a Lewis acid-base reaction occurs in which the molecule which act as Lewis base donate its electron pair into the empty orbital of an acid, forms Lewis acid-base adduct as shown in Figure 2.
The adduct formed contains a covalent coordinate bond between Lewis acid and Lewis base. The above explanation implies that the Lewis acid is a low electron density centre and Lewis base is a high electron density centre [ 6 ].
Acid-base neutralization. In this reaction, the two ammonia molecules reacts with silver ion. The ammonia has lone pair of electrons, so it has the ability to donate the lone pairs of electrons and acts as Lewis base. The positive charge on silver denotes its electrophilic nature that means it has an ability to accept the pairs of electrons and act as Lewis acid by Lewis definition.
Here, it can also be noted that when a Lewis acid reacts with a Lewis base, there is no change in the oxidation number of any of these atoms. This theory is not able to explain that why all acid-base reactions do not involve the covalent coordination bond.
This theory is also unable to explain the behavior of some acids like hydrogen chloride HCl and sulfuric acid H 2 SO 4 because they do not form the covalent coordination bond with bases. Hence, they are not considered as Lewis acids. This theory cannot explain the concept that why the formation of coordination bond is a slow process and acid-base reactions is a fast process. All Arrhenius acids and Bronsted Lowry acids are Lewis acids but reverse is not true.
Acids and bases are very important for modern society and in our daily lives. They exist everywhere in our body and in our surroundings. The theory that has been described in this chapter has given us all the basic information of acids and bases. In this chapter, we have discussed all the three basic theory of acid-base chemistry-Arrhenius theory, Bronsted-Lowry theory and Lewis acid-base theory.
Acids and bases have vital role in the area of medicine. From this concept, it is now easy to treat the diseases with the improved medicines by complex understanding of acids and bases. For example, If the concentration of hydrogen ion increases in the human blood, acidity increases that results weakness in body. In that condition, the body should keep alkaline by digesting food that produces alkali in the body, to neutralize the acidity. Definitely, without acids or bases information, our lives would look different to how it looks now.
Many products we are using today would have no use without this knowledge. I am eternally grateful and beholden to my family. My mother Mrs. Suman Munjal, Father Mr. Bhim Sain Munjal and sister Mrs. Shweta Java for strengthening me with the opportunities and experiences which enabled me in reaching these heights. The reason behind this success is their selfless encouragement that helped me explore new dimensions in my life.
I especially acknowledge the contribution of my confidence Dr. Himanshu Mathur and brother Mr. Chirag Munjal for his continuous and consistent support, efficient efforts of proof reading my works, kind words of motivation, and providing me with helpful tips.
I would like to show my appreciation for sharing his expertise and experiences for organizing required resources. I Shikha Munjal undersigned solemnly declare that all the information submitted by me in this chapter is correct, true and valid. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.
Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Ambrish Singh. We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract Swedish Svante Arrhenius, in proposed the concept of acid and base based on the theory of ionization.
Keywords acids and bases Arrhenius acid-base theory the water-ion system amphoteric nature of water hydrogen or hydronium ion. Introduction The concept of acids and bases have been defined many times in different ways. Whose definition of acids and bases emphasizes the role of protons? How many conjugate acid-base pairs participate in a Bronsted-Lowry acid-base reaction?
Which of the following is not a reactant in a neutralization reaction? Pure water partially breaks down into charged particles in a process called. Home Get App Take Quiz Create Which branch of chemistry deals with the mass relationships of elements in compounds and the mass relationships amond reactants and products in chemical reactions?
H 2 O 2 Compared with acids that have the suffiz -ic acids that have the suffiz -ous contain less oxygen Which acid is produced in the stomach? They increase the concentration of hydroxide ions in aqueous solution In water, hydroxides of Group 2 metals are all strong bases Many organic compunds, such as codeine, that contain nitrogen are weak bases Which of the following is a tripotic acid? H 3 PO 4 Whose definition of acids and bases emphasizes the role of protons?
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