1 / 23

Strong Bases (examples , pH calc. ) Acid-Base Theories Weak Electrolites

Dr. M. Sasvári: Medical Chemistry Lectures 3. Strong Bases (examples , pH calc. ) Acid-Base Theories Weak Electrolites. Strong bases Complete ionization in water. BOH. B + + OH -. I. II. III. IV. V. VI. VII. VIII. Li. Na. K. Remarks. Strong bases:.

yasir-simon
Download Presentation

Strong Bases (examples , pH calc. ) Acid-Base Theories Weak Electrolites

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dr. M. Sasvári: Medical Chemistry Lectures 3. • Strong Bases (examples, pH calc.) • Acid-Base Theories • Weak Electrolites Chem Eq 3

  2. Strong bases Complete ionization in water BOH B+ + OH- Chem Eq 3

  3. I. II. III. IV. V. VI. VII. VIII. Li Na K Remarks Strong bases: LiOH (Lithium hydroxide) removes CO2 in spacecraft's NaOH (Sodium hydroxide) oven cleaner, drain opener KOH (Potassium hydroxide) manufacturing liquid soaps Li+ + OH- K+ + OH- Na+ + OH- Strong bases Complete ionization in water Oxidation No.: +1 Chem Eq 3

  4. Example: 2K + 2H2O → 2K+ + 2OH - + H2 KOH is a strong base its formation: exergonic reaction heat → H2 gas ignites Chem Eq 3

  5. Strong bases I. II. III. IV. V. VI. VII. VIII. Ca Sr Ba Strong bases: Remarks Ca(OH)2(Calcium hydroxide) slaked lime (used in mortar) Sr(OH)2(Strontium hydroxide) Ba(OH)2(Barium hydroxide) X-ray of the stomach Ca2+ + 2OH- Sr2+ + 2OH- Ba2+ + 2OH- Complete ionization in water Oxidation No.: +2 Chem Eq 3

  6. NaOH Na+ + OH- Ca(OH)2 Ca2+ + 2 OH- Normality of a strong base = the [OH-]of the solution 1 N strong base contains 1 mol of OH-per liter Normality = Molarity * n (number of dissociable OH-) n = 1 n = 2 Chem Eq 3

  7. K+ KOH + OH- H2O H+ + OH- • pH of a strong base [OH-] = [ strong base] in Normality H+ from water [OH-] from water is negligible Chem Eq 3

  8. Examples KOH (N) pOH pH 13 1 [OH-]from H2O: 10-7 M [OH-]from KOH: 10-8 M 0.01 =10-2 2 12 11 0.001 =10-3 3 Total [H+] > 10-7 M • pH of a strong base pOH = - lg [OH-]= -lg c strong base (N) pH = 14 - pOH 14 1 =10 0 0 0.1 =10-1 =10-8 pOH < 7 pH > 7 The pH of a base is always above 7! Chem Eq 3

  9. g 4 mol 0.1 = Molarity = = mol = = 0.2 M pOH= -log10 (0.2)= 0.7 BASE! Mw 40 L 0.5 What is the M and N of the NaOH solution with pH 11.7? 4 g NaOH (Mw=40) is dissolved in water upto a total volume of 500 ml. What is the pH of the solution? = 0.1 0.2 N pH= 14-0.7=13.3 BASE! pOH= 14 – 11.7 = 2.3 10-2.3 =0.005 N 0.005 M Chem Eq 3

  10. Chem Eq 3

  11. EQ H2O H+ + OH- INI H2O H+ + OH- + OH- INI H2O H+ ACID added BASE added The Arrhenius concept (1884) • An acid, when dissolved in water, • increases the [ H+](decreases pH) • decreases [OH-] (increases pOH) • A base, when dissolved in water, • decreases the [ H+](increases pH) • increases [OH-] (decreases pOH) [H+] [OH-] [H+]  [OH-] Chem Eq 3

  12. The Bronsted-Lowry concept Acid = donates a proton in a proton-transfer reaction Conjugated base ACID Base = accepts a proton in a proton-transfer reaction Conjugated acid BASE Chem Eq 3

  13. - H A A + H H B B + H Protonated forms Deprotonated forms Bases Conjugated bases Acids Conjugated acids Chem Eq 3

  14. Conjugated BASE ACID CH3COO- CH3COOH + H+ Acetic acid Acetate ion CONJUGATED ACID BASE NH4+ ammonium ion ammonia NH3 + H+ Protonated forms Deprotonated forms Examples Chem Eq 3

  15. example: NH3 + H+ NH4 + H + H : : : H N : : H N H : : : + H+ H H The Lewis concept ammonia ammonium ion H+ accepts an electron pair Lewis acid NH3 donates an electron pair Lewis base Chem Eq 3

  16. example: 4 NH3 + Cu2+ [Cu(NH3)4]2+ H : : H N : 2+ : NH3 4 + Cu2+ H : H3N: Cu :NH3 : NH3 Tetraamminecopper(II) ion ammonia copper(II)ion The central metal ionaccepts an electron pair Lewis acid The ligand donates an electron pair Lewis base Complex ion(coordination compound) Chem Eq 3

  17. Weak electrolites • Degree of ionization (a) • - pKa, pKb • - Strength of Acidity/Basicity Chem Eq 3

  18. CH3COO-+ H3O+ CH3COOH + H2O hydroxonium ion acetic acid acetate ion INI 1M (excess) 1M 1M 0.006 M 0.006 M 0.006  = 0.003 = 2 moles in ionized form  = total number of moles Degree of Ionization 0 < < 1 Endergonic process, reaction goes backwards acetate ions will be protonated by the hydroxonium ion 0.006 M of the ionized forms remain in the new EQ EQ (2-0.006) M Degree of ionization (a) in the EQ: Chem Eq 3

  19. [H+] 10-4 0.01 or 1% a = = = c 0.01 [OH-] 10-3 0.05 or 5% a = = = c 0.02 The [H+] concentration of a 0.01 M monoprotic acid solution is 10-4. Calculate the degree of ionization! The [OH-] concentration of a 0.02M base solution is 10-3. Calculate the degree of ionization! Chem Eq 3

  20. (0.006)2 Ka = =1.8 10-5 (2-0.006) CH3COOH CH3COO - + H+  Ka =  2 c Ka = Ka = 1 -  Acidic Ionization Constant (pKa) acid Ka is an equilibrium constant of acidic dissociation (concentration of H2O included) Degree of Ionization (a) and the Ionization constant (Ka): c)c) c - c) c = total concentration (HA + A-) Chem Eq 3

  21. A-+ H3O+ AH + H2O 0.1 M 0.01 M 2 c Ka = 1 -  Will the a change if we dilute aweak acid? higher dilution  more complete ionization increase awill Ka = 1.7 10-5 a = 1.3 % a = 4.2 % Ka change! does not Chem Eq 3

  22. NH3 + H2O KOH NH4++ OH - K++ OH - Kb is an equilibrium constant of basic dissociation (concentration of H2O included) KOH Kb = KOH base 2 c Kb = 1 -  Basic Ionization Constant (pKb) in general: Chem Eq 3

  23. 7 4 2 pKa pK< 2 K> 10 -2 Strength of Acidity/Basicity the higher is the pKa/pKb the weaker is the acidity/basicity Strong acids and bases conjugated acids conjugated bases weak acids weak bases Chem Eq 3

More Related