C. Johannesson I. Introduction to Acids & Bases (p ) Ch. 15 & 16 - Acids & Bases

C. Johannesson A. Properties  electrolytes  turn litmus red  sour taste  react with metals to form H 2 gas  slippery to touch  turn litmus blue  bitter taste ChemASAP  vinegar, milk, soda, apples, citrus fruits  ammonia, lye, antacid, baking soda

C. Johannesson B. Definitions  Arrhenius - In an aqueous solution: HCl + H 2 O  H 3 O + + Cl – AcidsAcids form hydronium ions (H 3 O + ) (by releasing hydrogen ions into the water) H HHHH H Cl OO – + acid base

C. Johannesson B. Definitions  Arrhenius - In aqueous solution… BasesBases form hydroxide ions (OH - ) NH 3 + H 2 O  NH OH - H H H H H H N NO O – + H H H H base acid

C. Johannesson B. Definitions  Brønsted-Lowry Definitions: HCl + H 2 O  Cl – + H 3 O + AcidsAcids are proton (H + ) donors. BasesBases are proton (H + ) acceptors. conjugate acid conjugate base baseacid

C. Johannesson B. Definitions H 2 O + HNO 3  H 3 O + + NO 3 – CBCAAB

C. Johannesson B. Definitions NH 3 + H 2 O  NH OH - CACBBA

C. Johannesson B. Definitions - can be an acid or a base.  Amphoteric - can be an acid or a base.  Monoprotic- an acid that can only donate one H +  Polyprotic - an acid that can donate more than one H +

C. Johannesson B. Definitions F - H 2 PO 4 - H2OH2O HF H 3 PO 4 H 3 O +  Give the conjugate base for each of the following: - an acid with more than one H +  Polyprotic - an acid with more than one H +

C. Johannesson B. Definitions Br - HSO 4 - CO 3 2- HBr H 2 SO 4 HCO 3 -  Give the conjugate acid for each of the following:

C. Johannesson B. Definitions  Lewis AcidsAcids are electron pair acceptors. BasesBases are electron pair donors. Lewis base Lewis acid

C. Johannesson C. Strength  Strong Acid/Base 100% ionized in water strong electrolyte - + HCl HNO 3 H 2 SO 4 HBr HI HClO 4 NaOH KOH Ca(OH) 2 Ba(OH) 2

Acid Strength  Ternary: Strong if # oxygen - # hydrogen ≥ 2 H 2 SO 4 HNO 3 Weak if not! H 2 SO 3 HNO 2 LPChem:Wz

Acid Strength  Binary: Strong if HCl, HBr, HI Weak if not! H 2 O HF LPChem:Wz

Base Strength  Bases generally have the formula MOH, where M is a metal: Strong if M is from Group 1 or “heavy Group 2” (bottom of Gr2) Li, Na, K, Rb, Cs, Fr & Ca, Sr, Ba Weak if not! Mg(OH) 2 AgOH LPChem:Wz

C. Johannesson C. Strength  Weak Acid/Base does not ionize completely weak electrolyte - + HF CH 3 COOH H 3 PO 4 H 2 CO 3 HCN NH 3

Strong vs. Weak  Electrolyte: Conductive in aqueous solution.  Why do we need electrolytes? Muscle contractions are controlled by electrical messages of the nervous system. You sweat out electrolytes during a workout. They need to be replaced to keep things working. And to prevent muscle cramps (from insufficient electrolyte levels). LPChem:Wz - +

Strong vs. Weak  “Strong” substances (both acid and base) dissociate strongly.  Dissociate = break into ions Acid: HA  H + + A - Base: MOH  M + + OH -  Notice the arrows! These reactions go to completion. LPChem:Wz

Strong vs. Weak  These reactions go to completion. This means that a solution of the “strong acid” HCl doesn’t actually contain any HCl molecules. HCl  H + + Cl - All the HCl molecules dissociated. Now it is a solution of H + and Cl - ions. (We still label it “HCl” but it’s really H + + Cl - ) LPChem:Wz

Strong vs. Weak  “Weak” substances (both acid and base) dissociate weakly. Acid: HA ⇌ H + + A - Base: MOH ⇌ M + + OH -  Notice the arrows! These reactions DO NOT go to completion. They are at equilibrium. LPChem:Wz

Strong vs. Weak  Weak DO NOT go to completion. This means that a solution of the “weak acid” HF contains a mixture of HF molecules and H + and F - ions. HF ⇌ H + + F - Only a fraction of the HF molecules dissociated. Now the solution is a mixture of HF molecules, H + ions and F - ions. LPChem:Wz

Strong vs. Weak  End result:  Strong Acids & Bases dissociate all the way  (making all ions) and are therefore strong electrolytes  Weak Acids & Bases dissociate part way ⇌ (making only some ions) And are therefore weak electrolytes. LPChem:Wz