Acid–Base Titration Zagazig Universiy：–堿滴定酸扎加齊克大學(xué)

1、acid/base titration dr. hisham ezzat abdellatefprof. of analytical chemistry clinical pharmacy code: 105 electrolyte and the theory of electrolytic dissociation electrolytes conduct the electric current mineral acid, caustic alkalies and salts nonelectrolytes nonconducting solutions cane sugar, glyc

2、erin and ethyl acetate.acidbase titration pure water is a bad conductor of electricity acid as hcl h+ cl- base as koh k+ oh- salt as na2so4 na+ so42- molecule dissociation ions dissolved in waterstrong and weak electrolytes nacl na+ + cl k2so4 2k+ + so42 na2hpo4 2na+ + h+ + po43 arrhenius therefore

3、introduced a quantity a, called the degree of dissociation“ a“ = 1 strong electrolyte“ “a” very far from unity.= weak electrolyte law of mass action the rate of a chemical reaction is proportional to the active masses of the reacting substances. diluted solution concentrationlaw of mass action vf =

4、a.b. kf vb = c. d. kb kf a. b = kb c. dthe dissociation of water h2o h+ + oh h+ . oh = kw.(2) the ionic product of waterthe dissociation of water 25oc; the value of kw h+ . oh = 1014h+2 = kw = 1 x 1014 (3)hydrogen ion exponent (ph): h+ 106, 105 1 x 107 108 , 109 acid base neutral procedure for titra

5、tion ph is defined as equal to the logarithm of the hydrogen ion concentration with a negative sign.ph = log h+the ph scale1 2 3 4 5 6 7 8 9 10 11 12 13 14 stomach juice: ph = 1.0 3.0human blood: ph = 7.3 7.5lemon juice: ph = 2.2 2.4seawater: ph = 7.8 8.3vinegar: ph = 2.4 3.4ammonia: ph = 10.5 11.5c

6、arbonated drinks: ph = 2.0 4.0 0.1m na2co3: ph = 11.7orange juice: ph = 3.0 4.01.0m naoh: ph = 14.0figure : the ph scale and ph values of some common substancesfigure: a ph meterfigure: indicator paper being used to measure the ph of a solutionppkw = ph + poh ph = pkw pohor ph = 14 pohor poh = 14 ph

7、acids and bases: arrhenius theory acid h+ when dissolved in water bases, oh acid and base 3.6x10k)(hpo)(po(h po h hpo 2.0 x10k)po(h)(hpo(h hpo h poh1.1x10k)po(h)po)(h(h poh h poh1032k)(hso)(so(h so h hso1k)so(h)(hso(h hso h soh13-3243434247-2422424422-1434242432-4-24-24-4142-4-442alsoxph calculation

8、s1. solution of strong acids and strong basesh+ or oh =concentrationexample 1 calculate the ph value of a solution of a completely ionised 1.0 n solution of acid; or base. ? solution:h+ = 1m ph = log 1 = 0 (zero)similarly, in a completely ionised 1.0 n solution of base oh = 1 m poh = log 1 = 0 (zero

9、) example 2calculate the h+ and ph of 0.009 n hydrochloric acid? solution h+ = 0.009 nph = log (9.0 x 103) = log 9.0 log 103ph = 0.95 + 3.00 = 2.05example 3 calculate the ph values of a solution of sodium hydroxide whose oh is 1.05 x 103? solutionpoh = (log 1.05 + log 103)poh = (0.02 3 ) = 2.98ph =

10、14 2.98 = 11.02example 4 calculate the hydrogen ion concentration of a solution of ph 5.3? solutionph = log h+5.3 = log h+h+ = 5.01 x 106 mexample 5 calculate the hydroxyl ion concentration of a solution of ph 10.75 ?solutionpoh = 14 10.75 = 3.25oh = the antilog of 3.25oh = 5.62 x 104 mph calculatio

11、ns 2. solution of weak acids and bases a) calculation of ph of solution of weak acids ph = (pka + pca) b) calculation of ph of solution of weak bases: ph = pkw (pkb + pcb)ph of salts a) salts of strong acids or bases kcl k+ + cl- k+ + oh- kohcl- + h+ hclthe equilibrium between the hydrogen and hydro

12、xyl ions in water h2o h+ + oh b) salts of weak acids or bases (hydrolysis) salts of weak acids (or bases) react with water to give basic (or acidic) solutions hydrolysis reverse of neutralization i) salts of weak acids and strong bases:h2o + ch3coo ch3cooh + oh ph = (pkw pca + pka)scy h ii) salts of weak bases and strong acids:nh4+ + h2o nh4oh + h+ ph = (pkw + pcs