Some important points about acid,base and salts.....volume #1 ........Jus to add to our knowledge 1.Antoinne Lavoisier saw oxygen as d major element in all acids and proposed dat oxygen must be present in all acids until Humphrey Davy discovered HCl dat does not contain oxygen. 2.Svante Arrhenius in 1884 was d first man to propose a theory on acids and defined it as any substance dat is capable of releasing protons in aqeous solutions.d problems wit Arrhenius theory was dat it can only be effective in an aqeous solution.anoda problem was dat it does not see as acids any substance dat does not contain hydrogen ion(protons).lastly,Arrhenius theory saw hydroxyl ion as d only ion with basic properties. 3.Johanes Bronsted(Danish) and Thomas Lowry(English) carried out separate experiments in 1923 and reached similar conclusion dat acids are proton(hydrogenion) donors while bases are proton acceptors.d advantage of dis theory ova dat of Arrhenius is dat it can occur both in aqeous and non-aqeous media.but d problem it had was dat it is restricted to proton compounds alone i.e d compound must contain hydrogen b4 it can be called an acid.if no hydrogen,den it cant be an acid. 4.In d same 1923 d English Chemist G.N Lewis proposed a more generalized theory of acid and defined acids as substances dat can accept a pair of electrons and base as substances dat can donate a pair of electrons.d advantage of dis theory is dat it was not restricted to proton or hydrogen ions alone like d Arrhenius and Bronsted-Lowrys.d main advantage of dis theory ova d rest is dat it identifies as acids substances dat do not contain hydrogen.for example BF3,AlCl3,FeCl3 etc are all Lewis acids despite d fact dat dey do not contain hydrogens.dose substances can accept a pair of electrons frm substances like ammonia(Lewis base) wich posses pair of electrons to donate. 5.Conjugate bases are formed when an acid loses a proton or hydrogen ion e.g d conjugate base of H2SO4 is HSO4- as d acid wuld release a single proton or hydrogen ion to form d conjugate base.a conjugate acid is formed wen a base accepts a proton frm an acid.for example in d equation:HCl+NH3-----NH4+Cl- ammonium ion(NH4+) is d conjugate acid as it was formed frm d base ammonia by accepting a proton.while chloride ion(Cl-) is d conjugate base as it was formed frm d HCl acid wen it lost a proton or hydrogen ion.note dat conjugate base is always formed frm an acid while conjugate acid is always formed frm a base.in dat equation above dere r 2 acids.d original acid(HCl) and d conjugate acid(NH4+).also dere r 2 bases d original base(NH3) and d conjugate base(Cl-).HCl is d stronger acid bcos it was able to release its only proton or hydrogen ion to ammonia,why NH4+ is d weaker acid bcos it did not donate any proton but was formed as a result of d proton donated by a stronger acid(HCl).d strenght of an acid depends on it sole ability to release protons.d stronger base here is ammonia as it was able to capture d single proton frm HCl while chloride ion(Cl-) is d weaker base as it was not formed by accepting proton but by lose of proton frm an acid.d stronger an acid,d weaker its conjugate base and vice-versa.dere4 since HCl is a strong acid,its conjugate base Cl- wuld be weak and also since ammonia is a strong base,its conjugate acid(NH4+) wuld be weak and vice-versa....... Dis wuld be all 4 now,more to come shortly.have a great wikend ahead. #itsmeESQUIRE#
Posted on: Sat, 08 Mar 2014 06:51:08 +0000
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