Section 16.1 Properties of Acids and Bases 1.To understand two models of acids and bases 2.To understand how acids and bases ionize/dissociate in water Learning Goals

Section 16.1 Properties of Acids and Bases Acidic solutions have sour taste (tartness). Ex.: citric acid in lemons, limes, oranges; acetic acid in vinegar Basic (alkaline) solutions have bitter taste and are slippery. Ex.: soaps, “draino,” many household cleaning products

Section 16.1 Properties of Acids and Bases Acid, Base or Salt? NaCl NaOH Ba(OH) 2 HNO 3 H 2 SO 4 CaO HCl Mg(OH) 2 NH 3 LiOH LiF

Section 16.1 Properties of Acids and Bases Remember that… (add this to your notes) Acid + Base  Water + Salt Ex.: HCl + NaOH  H 2 O + NaCl Acid-Base Reactions (review) This is a double replacement reaction Because H + and OH -  H 2 O This is a neutralization reaction

Section 16.1 Properties of Acids and Bases Naming Acids (review) If anion does NOT contain oxygenIf anion contains oxygen Prefix hydro- Suffix –ic attached to root name of element suffix –ic if anion ends with –ate suffix –ous if anion ends with –ite attached to name of central element of anion / anion name The following compounds dissolve in water to form acids: HCl (hydrogen chloride)  hydrochloric acid HCN (hydrogen cyanide)  hydrocyanic acid H 2 S (dihydrogen sulfide)  hydrosulfuric acid Acid Anion Name H 2 SO 4 sulfate sulfuric acid H 3 PO 4 phosphate phosphoric acid H 2 SO 3 sulfite sulfurous acid HNO 2 nitrite nitrous acid

Section 16.1 Properties of Acids and Bases A. Acids and Bases – Two Models Acid – produces hydrogen ions (H + ) in aqueous solution H 2 O HCl(s)  H + (aq) + Cl - (aq) Base – produces hydroxide ions (OH - ) in aqueous solution H 2 O NaOH(s)  Na + (aq) + OH - (aq) The Arrhenius Model (older) – Dissociation Reactions

Section 16.1 Properties of Acids and Bases A. Acids and Bases – Two Models Acid – proton donor Base – proton acceptor The general reaction for an acid dissolving in water is The Bronsted-Lowry Model (newer) – Dissociation & Reaction with Water

Section 16.1 Properties of Acids and Bases A. Acids and Bases The Bronsted-Lowry Model Water acts as a base accepting a proton from the acid. Forms hydronium ion (H 3 O + )

Section 16.1 Properties of Acids and Bases A. Acids and Bases The Bronsted-Lowry Model Water acts as an acid, donating a proton to the base. Forms water molecule NaOH + H 2 O  Na + + OH - + H 2 O H+H+

Section 16.1 Properties of Acids and Bases Ammonia is a base because it accepts a proton and becomes the ammonium ion: NH 3 + H +  NH 4 + Ammonia ammonium, a polyatomic cation

Section 16.1 Properties of Acids and Bases A. Acids and Bases The Bronsted-Lowry Model Conjugate acid-base pairs

Section 16.1 Properties of Acids and Bases The Bronsted-Lowry Model - Identifying Acid-Base Pairs Do the two substances differ by a single proton? HF, F - conjugate pair: HF  H + + F - NH 4 +, NH 3 conjugate pair: NH 4 +  H + + NH 3 HCl, H 2 Onot a conjugate pair: Conj. base of HCl: Cl - Conj. acid of H 2 O: H 3 O +

Section 16.1 Properties of Acids and Bases The Bronsted-Lowry Model - Writing Conjugate Bases The acid and its conjugate base must differ by a single proton. Acid  proton + conjugate base 1.HClO 4  H + + ClO H 3 PO 4  H + + H 2 PO CH 3 NH 3 +  H + + CH 3 NH 2

Section 16.1 Properties of Acids and Bases Try to show the dissociation of each acid below into a proton and a conjugate base. Acid  proton + conjugate base 1.H 2 CO 3  H + + HCO H 3 BO 3  H + + H 2 BO H 3 PO 3  H + + H 2 PO HNO 2  H + + NO 2 -

Section 16.1 Properties of Acids and Bases To understand the concept of acid strength Learning Goals

Section 16.1 Properties of Acids and Bases B. Acid Strength Strong acid – completely ionizes / dissociates Forward reaction predominates Weak acid – most of the acid molecules remain intact

Section 16.1 Properties of Acids and Bases B. Acid Strength

Section 16.1 Properties of Acids and Bases B. Acid Strength A strong acid contains a relatively weak conjugate base. Water molecules compete with the base for the protons: a weak base loses (dissociation happens, strong acid), a strong base wins (little dissociation, weak acid)

Section 16.1 Properties of Acids and Bases B. Acid Strength Common strong acids are – Sulfuric acid, H 2 SO 4 – Hydrochloric acid, HCl – Nitric acid, HNO 3 – Perchloric acid, HClO 4 * Strong acids are strong electrolytes  good conductivity *

Section 16.1 Properties of Acids and Bases B. Acid Strength / Acid Types Oxyacid – acidic proton is attached to an oxygen atom – Typically a weak acid Organic acid – have a carbon atom backbone and commonly contain the carboxyl group

Section 16.1 Properties of Acids and Bases Acid Strength / Acid Types Monoprotic acids can furnish only one proton. Ex.: HCl  H + + Cl - Diprotic acids can furnish two protons. Ex.: H 2 SO 4  2H + + SO 4 2- Hydrohalic acids contain H attached to a halogen. Ex.: HCl (strong), HF (weak)

Section 16.1 Properties of Acids and Bases B. Acid Strength