Acids and Bases
Acids & BasesOur bodies contain many different kinds of fluid, these fluids are solutions and colloidal dispersion differ in their properties. The concentrations of various solutes in these solutions are delicately balanced in healthy person. Particularly important in the balance between acids and bases in the blood. Acids Are compound which have increase in hydrogen ion concentration. (H+) when dissolved in water. Bases Are compound which have increase in hydroxide ion concentration (OH-) when dissolved in water. Neutral solution Are compound which have an equilibrium between ( H+) and (OH-) Many concept are proposed to define acid & Base.
Arehenious Concept
Acids: any compound that forms a proton (H+) in aqueous solution, the proton does not exist in aqueous solution alone it surrounded when hydrated by H2O molecule to form (H3O+) hydroniuns ion H+ + H2O H3O+Strong acid ionized completely when dissolved in water like HCl, H2SO4, HNO3 HCl H+ + Cl- HNO3 H+ + NO-3weak acid ionized slightly when dissolved in water like acetic acid, HCN, HF. Formic Acid CH3COOH CH3COO- + H+ HCOOH HCOO- + H+Arehenious Concept cont.
Bases: Any compound that form OH ion like NaOH, KOH in aqueous solution strong bases ionized completely in water like NaOH, KOH, KOH K+ + OH- Weak bases ionized slightly in water like: NH3 +H2O NH4+ +OH-Neutralization:An acid react with abase to form water and salt.Bronisted – Lowry Concept
Acids: any compound or ion that donate proton When an acid donate a proton the remainder of the molecule or ion is bases called conjugated bases. HCL + H2O H3O + Cl- conjugated acid-base pair CH3COOH+ H2O CH3COO- + H3O conjugated acid-base pair NH3 + H2O NH4+ + OH- conjugatedNeutralization in Bronisted -Lowry Concept
It is transfer of the proton from an acid to base to form new acid & baseHCl + NH3 NH4+ + Cl-A.(1) B.(1) Acid(2) base(2) The water behave in Bronisted lowry, amphoteric behave, it mean when react with Acid it will be base & when react with base will be Acid H2O + H2O H3O+ + OH- With Acid it will accept proton & convert to H3O+ and with base it will donate proton & convert to OH- To determine the acidity and basicity of solution we use the pH scale.The pH scale
To determine the hydrogen ion concentration (H+) by this law pH = - log(H+) it is the minus log of hydrogen ion concentration pH- range between (1-14), (1-7) is acid range, (7-14) is a basic range. Acidic and basic solution are common in our life & many of them are body fluid's .The various body fluids differ in their acidity & their range of acidity example.Stomach juice pH-(1-3) acidicBlood plasma has pH- (7.3 – 7.4) if this value changed out side this rang the ability of Blood to transport O2 is reduced.Urine has pH between (5-8), it is wide pH-rang, it can be acidic or basic or neutral, it is due to the fact that many acidic & basic substance are removed from the body through the urine to maintain the pH rang of blood plasmaMeasuring of pH
The easiest most common and most accurate method of measuring pH in the laboratory is by means of an instrument called pH-meter. The acidity of a solution can be determined by an indicator which is an organic compound that changes their colore within characteristic pH-range a well known example is methyl-orange which it is colore in Alkaline medium is yellowish-orange colore & in acidic medium is red colore. The methode for determining the conc of Acid or base in a solution by using indicator it depend upon the chemical reaction between acid & base is called acid-base titration, it depend up on the balance between the conc of acid & base fo certian point called endpoint which appear by changing the colore of the solution (indicator) at equivalent point. The unite of conc. Of acid & base is called Normality.