Warm-Up What is an acid? What is a base? *Turn in your Lemonade POGIL (extra credit) *Get out your Molarity Practice What is an acid? What is a base?

Acids & Bases

Acid Properties Affect the color of indicators Neutralize bases to form water Acid (aq) + Base (aq)  Salt (aq) + H2O (l) React with metals to produce hydrogen gas Metal (s) + Acid (aq)  Salt (aq) + H2 (g) Taste sour Ex: Citric Acid (C6H8O7)

Acid Strength Strong acids completely dissociate in water, meaning all the molecules become ions HCl (aq) + H2O (l)  H3O+ (aq) + Cl- (aq) 7 of these: HCl, HBr, HI, HNO3, H2SO4, HClO3 HClO4 Weak acids do not dissociate easily, meaning only a few molecules become ions HC2H3O2 (aq) + H2O (l) ↔ H3O+ (aq) + C2H3O2- (aq) Common: H2CO3, HC2H3O2 H3O+ = Hydronium ion, same thing as H+ (aq)

Base Properties Affect the color of indicators Neutralize acids to form water Feel slippery Ex: Soaps Taste bitter Ex: Green vegetables

Base Strength Strong bases produce hydroxide ions in a solution Ca(OH)2 (aq)  Ca2+ (aq) + 2 OH- (aq) Ex: LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2 Weak bases do not dissociate in solution Ex: NH3, CO32-, ClO- Strong Bases= Group 1 and Group 2 hydroxides (except Beryillium and Magnesium) Lithium, rubidium, cesium and francium hydroxides are not normally used in lab because they are expensive.

Types of Acids & Bases Arrhenius Brønsted-Løwry Acid – a substance that can donate an H+ ion Base – any substance that can accept an H+ ion (has a lone pair) H+ ions are protons! Acid – a substance that can donate an H+ ion when dissolved in water Base – a substance that can donate a OH- ion when dissolved in water Acids & Bases defined by 3 different Theories: Bronsted-Lowry Arrhenius Lewis—Acids are electron pair acceptors; Bases are electron pair donors

Conjugate Pairs Pairs that differ by only one proton (H+) are called conjugate pairs A strong acid will make a weak conjugate base A weak acid will make a strong conjugate base Reversible reactions have an acid and base on both sides Reaction equilibrium will favor the side with the weaker acid and base The stronger the acid, the stronger its desire to dissociate (separate into ions). The resulting basic ion is weak because it does not want to reform the strong acid. If a strong acid had a strong conjugate base, then the base would quickly re-associate itself with a hydrogen proton. This reverses what the acid just did—dissociate itself from a hydrogen proton! Weak Acid + Weak Base <--> Strong Conj. Base + Strong Conj. Acid LEFT SIDE FAVORED!

Warm-Up What are the conjugate bases of these acids? (Hint: do acids accept or donate H+?) HI HSO4- H2CO3 HPO42-

Last Nights Homework C2H3O2- (aq) + H2O (l) ↔ HC2H3O2 (aq) + OH- (aq)  NH4+ (aq) + H2O (l) ↔ NH3 (aq) + H3O+ (aq)  C6H5NH2 (aq) + NH3 (aq) ↔ C6H5NH3 (aq) + NH2- (aq)

Last Nights Homework

pH Scale pH is a measurement of the concentration of H+ ions in solution pH = -log[H+] [H+] = 10-pH pOH is a measurement of the concentration of OH- ions in solution pOH = -log[OH-] [OH-] = 10-pOH In pure water, pH and pOH are both 7 Kw = [H+][OH-] = 1 x 10-14 pH + pOH = 14 Kw= the autoionization constant of water

pH Conversions

Practice If [H+] = 1.0 x 10-7 M, then what is the pH? pH = 7.0

Practice If [OH-] is 5.01 x 10-4 M, what is the pOH? pOH = 3.30

Practice In household bleach, the concentration of OH- ions is 5.0 x 10-2 M. What is the pH? pOH = 1.3 pH = 12.7

pH Indicators Litmus Paper Universal Indicator

pH Indicators Methyl Red Bromothymol Blue Phenolphthalein