Acids and Bases Ch 16

I. Properties of Acids and Bases A. Acids –1. Taste sour (think lemons: citric acid) –2. React with metals to produce hydrogen –3. Conduct electricity B. Bases –1. Taste bitter (think Milk of Magnesia) –2. Feel slippery (like soap) –3. Conduct electricity –4. Can be caustic

C. The Arrhenius Model 1. Svante Arrhenius was 1 st person to recognize the properties of acids and bases. –a. Arrhenius Acid- produces H + ions in solution HCl(aq) → H + (aq) + Cl - (aq) –b. Arrhenius Base- produces OH - ions in solution NaOH(aq) → Na + (aq) + OH - (aq)

D. Brønsted- Lowry Model 1. Johannes Brønsted and Thomas Lowry developed a more general definition of acids and bases. –a. Brønsted- Lowry acid- a proton (H + ) donor –b. Brønsted- Lowry base- a proton (H + ) acceptor –c. Conjugate base- the remaining substance after an acid has donated its proton –d. Conjugate acid- the remaining substance after a base has accepted a proton.

Example HCl(aq) + H 2 O(aq) → H 3 O + (aq) + Cl - (aq) BL acid BL base Conj Conj acid base HSO 4 - (aq) +H 2 O(aq) → H 2 SO 4 (aq) + OH - (aq) BL base BL acid Conj Conj acid base H 3 O + is called the hydronium ion.

Problems to try 1. Which of the following represent conjugate acid-base pairs? –a. HF, F - b. NH 4 +, NH 3 c. HCl, H 2 O 2. Write the conjugate base for each of the following: –a. HClO 4 b. H 3 PO 4 c. CH 3 NH 3 +

C. Acid Strength 1. strong acids and bases: break apart 100% into their ions in solution

2. weak acids and bases: only 5% breaks down into ions in solution.

Hydronium Ion Concentration [H 3 O + ] –It’s sometimes written as [H + ] as a short cut, because we are just concerned about the H. Tells how concentrated the acid/ base is in terms of MOLARITY!!!!!

pH pH gives the relative strength of an acid or base! pH = -log [H + ] pOH = -log [OH - ] pH + pOH = 14 [H + ] [OH - ] = 1 ×

3. Strong Acids –a. have weak conjugate bases –HClO 4 –HI –HBr –H 2 SO 4 –HCl –HNO 3

–b. Diprotic acids- an acid that can give 2 protons H 2 PO 4 (aq) → H + (aq) + HPO 4 - (aq) –HPO 4 - (aq) → H + (aq) + PO 4 2- (aq) –c. Triprotic acids- an acid that can give 3 protons H 3 PO 4 (aq) → H + (aq) + H 2 PO 4 - (aq) –H 2 PO 4 - (aq) → H + (aq) + HPO 4 2- (aq) »HPO 4 2- (aq) → H + (Aq) + PO 4 3- (aq)

4. Strong Bases Have a weak conjugate acid Alkali Metal Hydroxides NaOH KOH LiOH RbOH CsOH Alkaline Earth Metal Hydroxides Ca(OH) 2 Ba(OH) 2 Sr(OH) 2 While these 3 are strong bases, they are not very soluble in water.