1 ACID- BASE EQUILIBRIA ACID- BASE EQUILIBRIA ACID- BASE EQUILIBRIA ACID- BASE EQUILIBRIA

LEWIS ACIDS & BASES ACID = ELECTRON PAIR ACCEPTOR BASE = ELECTRON PAIR DONOR MUST HAVE AN UNSHARED PAIR OF ELECTRONS TO DONATE TO THE COVALENT BOND BETWEEN THE ACID AND BASE H + + NH 3 NH 4 1+ H + + H N H H : H N H H + Al H 2 O Al(H 2 O) 6 H 2 O + SO 3 H 2 SO 4 BF 3 + NH 3 BF 3 - NH 3

BRONSTED - LOWRYBRONSTED ACIDS AND BASES SPECIAL CASE OF THE LEWIS ACID-BASE THEORY ACID IS A PROTON DONOR H+H+ BASE IS A PROTON ACCEPTOR MUST HAVE UNSHARED PAIR OF ELECTRONS O + NH 3 o C H3CH3C O O H o C H3CH3C O o - + THAT IS, MUST BE A LEWIS BASE ACID - BASE REACTION NEUTRALIZATION PROTON BOUND TO A VERY ELECTRONEGATIVE ATOM NOT AN ACID PROTON

ACID: ARRHENIUS: PRODUCES H 1+ IN WATER BASE: ARRHENIUS: PRODUCES OH 1- IN WATER BRONSTED: PROTON DONOR BRONSTED: PROTON ACCEPTOR LEWIS: HAS EMPTY ORBITAL LEWIS: HAS e - PAIR AVAILABLE TO SHARE + SALT + WATER NEUTRALIZATION DIFFERENCE: BRONSTED ACID HAS A PROTON!

NAMING ACIDS BINARY: UNLESS DISSOLVED IN WATER -- COVALENT HBr HYDROGENHYDROBROMIDEBROMIC HYDROBROMICACID HF HI HYDROFLUORIC ACID HYDROIODIC ACID POLYATOMIC ANIONS -ITE = OUS OR -ATE = IC EXCEPTING S OR P CO 3 2- CARBONATE ION H 2 CO 3 IC ACID SO 4 2- = SULFATE ION H 2 SO 4 = SULFURIC ACID SO 3 2- = SULFITE ION H 2 SO 3 = SULFUROUS ACID

ACID BASE ACID CONJUGATE BRONSTED ACID-BASE CONJUGATE PAIRS HCOOH (aq) + H 2 O (l) HCOO 1- (aq) + H 3 O 1+ (aq ) HOBr (aq) + H 2 O (l) OBr 1- (aq) + H 3 O 1+ (aq ) CONJUGATE CONJUGATE PAIRS DIFFER BY A SINGLE PROTON!!! O + NH 3 o C H3CH3C O O H o C H3CH3C O o - +

CH 3 COOH (aq) + NH 3 (aq) CH 3 COO 1- (aq) + (aq) a IF K >> 1, DISSOCIATION IS EXTENSIVE REACTION IS EXTENSIVE IF K << 1, DISSOCIATION IS NOT EXTENSIVE THE LARGER THE VALUE OF K, THE MORE EXTENSIVE IS THE REACTION

H 2 S (aq) + H 2 O (l)  HS 1- (aq) + H 3 O 1+ (aq) K = [HS 1- ] [H 3 O 1+ ] [ H 2 S] a K b = 1 X / K a THE LARGER THE VALUE OF K, THE STRONGER IS THE ACID OR THE BASE FOR ACID: THE MORE H 3 O 1+ ION IS PRODUCED FROM ACID - BASE CHART: HIGH K a + HIGH K b = EXTENSIVE REACTION RESULT: K>1 IF PRODUCT IS THE WEAKER ACID OR BASE OF THE CONJUGATE PAIR

ACID-BASE STRENGTH BINARY HA STRENGTH OF THE HA BOND ELECTRONEGATIVITY OF A OXOACID (OXYANION) X - O - H OXIDATION STATE OF X ELECTRONEGATIVITY OF X USUALLY: STRONGER BOND = WEAKER ACID RESULT: K>1 IF PRODUCT IS THE WEAKER ACID OR BASE OF THE CONJUGATE PAIR

H 2 O (l) + H WEAK ACID: K a < K a FOR H 3 O 1+ K a << 1 STRONG ACIDS: HX WHERE X = Cl, Br, I HNO 3, HClO 4, H 2 SO 4 WEAK BASE: K b < K a FOR H 3 O 1+ K b << 1 STRONG BASE:SOLUBLE METAL HYDROXIDE

H 2 O (l) + H 2 O (l) H 3 O 1+ (aq) + OH 1- (aq) K = K w = [H 3 O 1+ ][OH 1- ]= 1.0 x AT 25 o C [H 3 O 1+ ] > [OH 1- ] ACIDIC SOLUTION [H ] = [OH 1- ] NEUTRAL SOLUTION [H 3 O 1+ ] < [OH 1- ] BASIC SOLUTION [H 3 O 1+ ] = [OH 1- ] = 1.0x10 -7 M pH = -log [H 3 O 1+ ] <7 = 7 >7 pK = -logK a -log[1.0x10 -7 ] pK a + pK b = 14pH + pOH = 14K a x K b = 1.0 x

pOH pH Scales to determine Acidity or Alkalinity

NEUTRAL ACIDIC BASIC GASTRIC JUICE, 0.1 M HCl ORANGE JUICE COKE, VINEGAR WINE TOMATO, BEER BLACK COFFEE RAIN SALIVAURINE HUMAN MILK BLOOD, TEARS SEAWATER, EGG WHITE BILE BAKING SODA BORAX NAIR HOUSEHOLD AMMONIA DRAIN CLEANER, 0.1 M NaOH

14 WHAT IS THE pH of: A. SOLUTION WHERE [H 3 O 1+ ] = 3.6x10 -6 M B M HCl C. SOLUTION WHERE [OH 1- ] = 2.5x10 -3 M WHAT IS THE [OH 1- ] CONC. OF A pH = 4.5 SOLUTION? pH =-log[H 3 O 1+ ] K w = [H 3 O 1+ ][OH 1- ] = 1.0 x A. pH = - LOG[3.6x10 -6 ]= 5.4(AN ACIDIC SOLUTION) B. pH = -LOG[0.25] = 0.60 C.[H 3 O 1+ ] [2.5x10 -3 ] = 1.0x = 4.0x pH = -LOG[4.0x ] = 11.4 (A BASIC SOLUTION) [3.2x10 -5 ][OH 1- ] = 1.0 x [H 3 O 1+ ] = 10 -pH = = 3.2x10 -5 = 3.1x M

[H + ]pH[OH - ]pOH Acid, Base or Neutral

Titration Sample problem What volume of 1.0 M HCl is needed to neutralize 30.0 mL of 2.5 M NaOH?

Try These: What is the molarity of 5.0 mL of acid used to neutralize 10.0 mL of 2.5 M base? What volume of 1.0 M base is needed to neutralize 20.0 mL of 2.3 M acid?