Acids and Bases

Acids & Bases Our 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. n Acids Are compound which have increase in hydrogen ion concentration. (H + ) when dissolved in water. n Bases Are compound which have increase in hydroxide ion concentration (OH - ) when dissolved in water. n 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 H 2 O molecule to form (H 3 O + ) hydroniuns ion H + + H 2 O  H 3 O + Strong acid ionized completely when dissolved in water like HCl, H 2 SO 4, HNO 3 HCl  H + + Cl - HNO 3  H + + NO - 3 weak acid ionized slightly when dissolved in water like acetic acid, HCN, HF. Formic Acid CH 3 COOH  CH 3 COO - + H + HCOOH  HCOO - + H +

Arehenious Concept 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: NH 3 +H 2 O  NH 4 + +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 + H 2 O  H 3 O + Cl - conjugated acid-base pair CH 3 COOH+ H 2 O  CH 3 COO - + H 3 O conjugated acid-base pair NH 3 + H 2 O  NH OH - conjugated

Neutralization in Bronisted -Lowry Concept It is transfer of the proton from an acid to base to form new acid & base HCl + NH 3  NH 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 H 2 O + H 2 O  H 3 O + + OH - With Acid it will accept proton & convert to H 3 O + 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. 1. Stomach juice pH-(1-3) acidic 2. Blood plasma has pH- (7.3 – 7.4) if this value changed out side this rang the ability of Blood to transport O 2 is reduced. 3. 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 plasma

Measuring 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.

Normality n Is the no of equivalent of acid or base per liter of solution? n miliequivalent n Or Normality (N) = is the no of (meq) of acid or base per 1ml of solution n n No of equivalent of A or B n N = ــــــــــــــــــــــــــــــــــــــــــــــــــــــــ n Volume of solution ( L ) n n no of m.equivale of A. or B n Or N = ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ n Volume of solution (1 ml) n no of equivalent = wt/equivalent ml n wt wt x 1000 n N= ــــــــــــــــــــــــــــ or = ـــــــــــــــــــــــــــ n e.q.wtXVu) equivint x VCml) n wt

Buffer Solution n Is a mixture of either weak acid & it's salt or weak base & it's salt small addition of either strong acids or strong bases causes little change in it's PH like acetic acid & sodium acetate, (CH 3 COOH & CH 3 COONa). Buffer solutions are important in the body because they maintain the acid base balance in the blood.

Catalysis & Catalyst Compound allow the reaction to occur & don't inter in the chemical reaction they increase the speed of the reaction, some of catalyst is sample like H 2 O, other catalyst are complicated as enzyme & their effect is called catalysis.