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Hand in homework (Models 1, 2, 3) NOW for credit ( no late ones accepted)

Hand in homework (Models 1, 2, 3) NOW for credit ( no late ones accepted) Pick up NEW worksheet (Model 4) Review Models 1, 2, 3 (homework) Work on Model 4 in class. Model 1. Bronsted - Lowry Definition: Acid : substance that donates a H + to another species

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Hand in homework (Models 1, 2, 3) NOW for credit ( no late ones accepted)

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  1. Hand in homework (Models 1, 2, 3)NOW for credit (no late ones accepted) • Pick up NEW worksheet (Model 4) • Review Models 1, 2, 3 (homework) • Work on Model 4 in class

  2. Model 1 Bronsted- Lowry Definition: Acid: substance that donates a H+ to another species Base: substance that accepts a H+ from another species HCl (g) + H2O (l) H3O+ (aq) + Cl- (aq) Forward reaction Reverse reaction HClCl- conjugate acid/ base pair H2O H3O+

  3. Model 1: more examples • What is conjugate base of acid HF? F- • What is conjugate acid for base CH3NH2? CH3NH3+

  4. Model 2 More restrictive definition Arrhenius definition: Acid: substance produces H3O+ in water when dissolved Base: substance produces OH- in water when dissolved HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq) H2O (l) + H2O (l) H3O+ (aq) + OH- (aq) K = [OH-][H3O+] Kw = 1.0 x 10-14 1.0 x 10-14 = x2; x = 1.0 x 10-7 M [OH-] = [H3O+] = 1.0 x 10-7 M

  5. Model 3 • pH = -log [H3O+] • [H3O+] = 10-pH (take the negative antilog) • pOH = -log [OH-] • [OH-] = 10-pOH • pH scale ranges from 1-14 • Lower pH = more acidic; Higher pH = more basic • pH + pOH = 14.00

  6. Model 3 continued • Calculate pH and pOH for at least 2 of the substances.

  7. Model 3 Answers

  8. Model 4- New Worksheet

  9. Model 4 continued • Information for question 4.9: (K or Ka = acid dissociation constant) • Strong acid, K>>1, large dissociation constant • Weak acid, K < 1, small dissociation constant HCl(g) + H2O(l) H3O+(aq) + Cl-(aq) K = 2 x 104 NH3(aq) + H2O(l) OH-(aq) + NH4+(aq) K = 3 x 10-7 HCN(aq) + H2O(l) H3O+ (aq) + CN-(aq) K = 3 x 10-11

  10. Summary Summary • Bronsted Lowry definition – more commonly used • Arrhenius definition – more restrictive • conjugate acid/base pair – differ by a H+ • Kw = 1.0 x 10-14; [H3O+]= [OH-] for water • pH = -log [H3O+]; pOH = -log[OH-] • Strong acid, K>>1 • Weak acid, K < 1

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