A: Acid-Base Theory The Arrhenius-Ostwald Theory of acids and bases The first acid and base theory was formulated by Swedish scientist Svante August Arrhenius (1859-1927) in 1887. The first ideas about dissociation of molecules of electrolytes (substances whose solutions and melts conduct electric current) in solution arose at the time when Arrhenius wrote his doctoral dissertation in 1883. Working in the Riga Polytechnic Institute in the winter of 1886 with a German-Russian chemist Wilhelm Ostwald (1853-1932), Arrhenius investigated the electrical conductivity of aqueous solutions of various substances. Based on results received in this investigation he developed his theory of acids and bases . The essence of the hypothesis was that …show more content…
Arrehnius did not explain how acids and bases behave in a non aqueous solution. For example, there is dissociation of acetic acid in methanol: CH3CO2H + CH3OH ⇄ CH3CO2− + CH3OH 2. He claimed that an acid should be an acid in any solvent. However, there is rebuttal nowadays. For example, dissolving in water, HCL behaves as Arrhenius acid but dissolving in benzene there is no dissociation. This is the discrepancy to Arrhenius theory. He stated that dissociation occurs in any aqueous solution. 3. Arrhenius proposed the formula NH4OH as the formula for ammonia in water because of the need for hydroxide as the base. This led to the opinion that NH4OH is the base while NH3 is an actual base. (Arrhenius theory, n.d.) Bronsted-Lowry acid-base …show more content…
For explanation of reactions occurring in non-protonic solvents such as COCl2, SO2,N2O4… the protonoic definition can not be used. 2. This theory can not explain the reactions between acidic oxides such as SO3, CO2 and basic oxides such as CaO, BaO which take place even in the absence of the solvent: CaO+SO3->CaSO4. There is no proton transfer. 3. Substances such as BF3, ALCL3 do not have any hydrogen and can not donate the proton but they behave as acids. Lewis acid-base theory In 1923, G.N. Lewis from UC Berkeley proposed an alternate theory for description of acids and bases. His theory based on structure and bonding and gave general explanation of bases and acids.. Due to the Lewis definitions of bases and acids it is possible for chemists to predict acid-base reactions. Acoordinate covalent bond is produced by the reaction of a Lewis acid and a Lewis base. According to this theory: • Acid-any species which is capable of receiving a pair of electrons • Base-any species which is capable of donating a pair of electrons (Oxford University Press, 2016) Ammonia also known as “alkaline air” was discovered in gaseous form by Joseph Priestley in 1774.