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Acids and Bases

Acids and Bases. Properties of Acids. Produce H + (as H 3 O + ) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) Taste sour Corrode metals Good Electrolytes React with bases to form a salt and water pH is less than 7

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Acids and Bases

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  1. Acids and Bases

  2. Properties of Acids • Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) • Taste sour • Corrode metals • Good Electrolytes • React with bases to form a salt and water • pH is less than 7 • Turns blue litmus paper to red “Blue to Red A-CID”

  3. Properties of Bases • Generally produce OH- ions in water • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water • pH greater than 7 • Turns red litmus paper to blue “BasicBlue”

  4. Naming Acids Binary Acid – An acid that contains only two elements, one of which is hydrogen and one which is more electronegative. • HF – Hydrofluoric acid • HCl – Hydrochloric acid • Oxyacid – An acid that has hydrogen, oxygen, and a third element that is usually a non-metal • HClO4 – Perchloric acid • HNO2 – Nitrous acid • H2CO3 – Carbonic acid

  5. Arrhenius Definition Acid - Substances in water that increase the concentration of hydrogen ions (H+). Base - Substances in water that increase concentration of hydroxide ions (OH-). Problem – many bases do not actually contain hydroxides

  6. Bronsted-Lowry Definition Acid - neutral molecule, anion, or cation that donates a proton. Base - neutral molecule, anion, or cation that accepts a proton. HA + :B HB+ + :A- HCl + H2O  H3O+ + Cl- Acid Base Conj Acid Conj Base

  7. Conjugate Acid Base Pairs • Conjugate Base - The species remaining after an acid has transferred its proton. • Conjugate Acid - The species produced after base has accepted a proton. • HA & :A- - conjugate acid/base pair • :A- - conjugate base of acid HA • :B & HB+ - conjugate acid/base pair • HB+ - conjugate acid of base :B

  8. Examples of Bronsted-Lowry Acid Base Systems • Note: Water can act as acid or base • Acid Base Conjugate AcidConjugate Base • HCl + H2O  H3O+ + Cl- • H2PO4- + H2O  H3O+ +HPO42- • NH4+ + H2O  H3O+ + NH3 • Base Acid Conjugate AcidConjugate Base :NH3 + H2O  NH4++ OH- • PO43- + H2O  HPO42- + OH-

  9. Diprotic and Triprotic Acids (Polyprotic) Sulfuric Acid can donate two protons per molecule Phosphoric acid can donate three protons per molecule • H3PO4 + H2O  H3O+ + H2PO4- • H2PO4- +H2O  H3O+ + HPO42- • HPO42- +H2O  H3O+ + PO43-

  10. G.N. Lewis Definition • Lewis • Acid - an electron pair acceptor • Base - an electron pair donor

  11. Common Strong Acids/Bases Strong Acids Hydrochloric Acid Nitric Acid Sulfuric Acid Perchloric Acid Strong Bases Sodium Hydroxide Potassium Hydroxide *Barium Hydroxide *Calcium Hydroxide *While strong bases they are not very soluble

  12. Acid Strength • As acid strength decreases, base strength increases • The stronger the acid, the weaker its conjugate base • The weaker the acid, the stronger its conjugate base

  13. Base Strength • As base strength decreases, acid strength increases • The stronger the base, the weaker its conjugate acid • The weaker the base, the stronger its conjugate acid

  14. Salts & Neutralization • A salt is the neutralization product of an acid and a base. • The anion comes from the acid and the cation from the base. • Examples HCl + NaOH  NaCl + H2O. H2SO4 + 2 KOH  K2SO4 + H2O.

  15. The pH Scale pH [H3O+ ] [OH- ] pOH

  16. pH and acidity • Acidity or Acid Strength depends on Hydronium Ion Concentration [H3O+] • The pH system is a logarithmic representation of the Hydrogen Ion concentration (or OH-) as a means of avoiding using large numbers and powers. pH = - log [H3O+] pOH = - log [OH-] 3. What is the pH of a solution if the [H3O+] is 3.4 x 10-5 M? pH = -log [H3O+] = -log(3.4 x 10-5) = 4.47

  17. pH and acidity Kw = [H3O+] [OH-] = 1.0 x10-14 In pure water [H3O+] = [OH-]= 1.0 x10-7 pH + pOH = 14

  18. Indicators

  19. pH and acidity The pH values of several common substances are shown at the right. Many common foods are weak acids Some medicines and many household cleaners are bases.

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