1. Acids and Bases: Qualitative and Quantitative Approaches SCH4U1 Unit 5

2. Acids and Bases So Far… Grade 10 Nomenclature and formulas Properties of acids and bases Arrhenius definition (HX = acid; XOH = base) Grade 11 Brønsted-Lowry definition Strong vs weak, concentrated vs. dilute pH scale Acid-base titrations

3. Qualitative Properties of Acids and Bases

4. Acids Soluble is water Soluble is water Sour taste Sour taste Watery feel Watery feel Electrolyte Electrolyte React w/ metals to make H 2 React w/ metals to make H 2 Formed by non-metal oxides + water (SO 3 + H 2 O) Neutralize bases Neutralize bases Turns litmus red Turns litmus red Bases Soluble or insoluble Bitter taste Soapy feel Electrolyte No reaction w/ metals Formed by metal oxides + water (Na 2 O + H 2 O) Formed by metal oxides + water (Na 2 O + H 2 O) Neutralize acids Turns litmus blue

5. Chemical Definitions of Acids & Bases 1)Arrhenius Theory (1884) Based on dissociation in water. 2) Brønsted-Lowry Theory (1923) Based on proton (H + ) transfer in reactions. 3) Lewis Theory (1923) Based on electron pair transfer.

6. Electrolytes: compounds that dissociates or ionizes when dissolved in water (e.g. NaCl) NaCl Na + (aq) + Cl - (aq) Electrolytes conduct electricity when dissolved. Water is a very weak electrolyte. ≈ 0% H 2 Ono reaction Acid-Base Key Terms 100%

7. Strong Acid/Base: Acids or bases that ionize (dissociate) 100%. Strong Acids: HCl, HBr, HI, HNO 3, HClO 4, H 2 SO 4 * (1 H) HBr (aq) H + (aq) + Br - (aq) 100% Strong Bases: LiOH, NaOH, KOH, RbOH, CsOH (soluble) Mg(OH) 2, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2 (insoluble) CsOH (s) Cs + (aq) + OH - (aq) 100% All other acids or bases are weak.

8. Two Important Ions Hydronium (protonated water) Hydroxide (deprotonated water)

9. Monoprotic: Acids containing only one ionizable hydrogen (e.g. HCl). Diprotic: Acids containing two… (e.g. H 2 CO 3 ) Triprotic: Acids containing three… (e.g. H 3 PO 4 ) Polyprotic Acids

10. Amphoteric: A substances capable of acting like acids OR bases in BL acid-base reactions. HSO 4 - (aq) + H 2 O ⇌ SO 4 2- (aq) + H 3 O + (aq) BL Acid BL Base CBCA HSO 4 - (aq) + H 2 O ⇌ H 2 SO 4 2- (aq) + OH - (aq) BL Base BL Acid CACB

11. Quantitative Properties of Acids and Bases

12. Water itself never consists of “pure” H 2 O. Water constantly undergoes autoionization to produce these ions: H 2 O (l) H + (aq) + OH − (aq) or more accurately, H 2 O + H 2 O (l) H 3 O + (aq) + OH − (aq) acidbase conj. acid conj. base

13. Ion Product Constant of Water (K w ) The equilibrium constant equation for this autoionization process can be written as: K w = [H 3 O + ][OH − ] = Therefore for “pure” water: [H 3 O + ] = [OH − ] = 1.0 x 10 -14 (at 25 o C) 1.0 x 10 -7 mol/L

14. So what really is an acid & base?! Water undergoes autoionization in all aqueous solutions. If an acid or a base is dissolved in water, then [H 3 O + ] ≠ [OH − ], but the product of their concentration always equals 1.0 x 10 -14 or K w. In all aqueous solutions: 2H 2 O (l) H 3 O + (aq) + OH − (aq) K w = [H 3 O + ][OH − ] = 1.0 x 10 -14

15. Defining Neutral, Acidic & Basic For an aqueous equilibrium: Solution is neutral:[H 3 O + ] = [OH − ] Solution is acidic:[H 3 O + ] > [OH − ] Solution is basic:[H 3 O + ] < [OH − ]

16. Problem Solving with Strong Acids and Bases Refer to the sample questions on quantitative aspects of acids and bases.