Acids. Names of Acids. Naming Some Common Acids. Solution. Learning Check Acids and Bases. Arrhenius acids Produce H + ions in water.

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1 Chapter 10 Acids and Bases Acids 10.1 Acids and Bases Arrhenius acids Produce H + ions in water. H 2 O HCl(g) H + (aq) + Cl (aq) Are electrolytes. Have a sour taste. Turn litmus red. Neutralize bases. 1 2 Names of Acids Naming Some Common Acids Acids with H and a nonmetal are named with the prefix hydro and end with ic acid. HCl hydrochloric acid Acids with H and a polyatomic ion are named by changing the end of the name of the polyatomic ion from ate to ic acid or ite to ous acid. ClO 3 chlorate ClO 2 chlorite HClO 3 chloric acid HClO 2 chlorous acid TABLE Select the correct name for each of the following acids: A. HBr 1. bromic acid 2. bromous acid 3. hydrobromic acid B. H 2 CO 3 1. carbonic acid 2. hydrocarbonic acid 3. carbonous acid C. HBrO 2 1. bromic acid 2. hydrobromous acid 3. bromous acid A. HBr 3. hydrobromic acid The name of an acid with H and one nonmetal uses the prefix hydro and ends with ic acid. B. H 2 CO 3 1. carbonic acid An acid with H and a polyatomic ion is named by changing the end of an ate ion to ic acid. C. HBrO 2 3. bromous acid This acid of bromite (BrO 2 ) is bromous acid

2 Bases Arrhenius bases Produce OH ions in water. Taste bitter or chalky. Are electrolytes. Feel soapy and slippery. Neutralize acids. Some Common Bases Bases with OH ions are named as the hydroxide of the metal in the formula. NaOH sodium hydroxide KOH potassium hydroxide Ba(OH) 2 barium hydroxide Al(OH) 3 aluminum hydroxide Fe(OH) 3 iron(iii) hydroxide 7 8 Match the formulas with the names: A. HNO 2 1) iodic acid B. Ca(OH) 2 2) sulfuric acid C. H 2 SO 4 3) sodium hydroxide D. HIO 3 4) nitrous acid E. NaOH 5) calcium hydroxide Match the formulas with the names: A. 4 HNO 2 nitrous acid B. 5 Ca(OH) 2 calcium hydroxide C. 2 H 2 SO 4 sulfuric acid D. 1 HIO 3 iodic acid E. 3 NaOH sodium hydroxide 9 10 Comparing Acids and Bases TABLE 10.2 Identify each as a characteristic of an (A) acid or (B) base. 1. Has a sour taste. 2. Produces OH in aqueous solutions. 3. Has a chalky taste. 4. Is an electrolyte. 5. Produces H + in aqueous solutions

3 Chapter 10 Acids and Bases Identify each as a characteristic of an (A) acid or (B) base BrØnstedLowry Acids and Bases A 1. Has a sour taste. B 2. Produces OH in aqueous solutions. B 3. Has a chalky taste. A, B 4. Is an electrolyte. A 5. Produces H + in aqueous solutions BrØnstedLowry Acids and Bases NH 3, A BrØnstedLowry Base According to the BrØnstedLowry theory, Acids donate a proton (H + ). Bases accept a proton (H + ). In the reaction of ammonia and water, NH 3 is the base that accept H +. H 2 O is the acid that donates H Conjugate AcidBase Pairs Conjugate Acids and Bases In any acidbase reaction, there are two conjugate acidbase pairs Each related by the loss and gain of H +. One occurs in the forward direction. One occurs in the reverse direction. conjugate acidbase pair 1 HA + B A + BH + In this acidbase reaction, An acid HF donates H + to form its conjugate base F. A base H 2 O accepts H + to form its conjugate acid H 3 O+. There are two conjugate acidbase pairs. conjugate acidbase pair

4 Conjugate AcidBase Pairs In the reaction of HF and H 2 O One conjugate acidbase pair is HF/F. The other conjugate acidbase pair is H 2 O/H 3 O +. Each pair is related by a loss and gain of H +. Conjugate AcidBase Pairs In the reaction of NH 3 and H 2 O, One conjugate acidbase pair is NH 3 /NH 4 + The other conjugate acidbase is H 2 O/OH A. Write the conjugate base of the following: 1. HBr 2. H 2 S 3. H 2 CO 3 B. Write the conjugate acid of the following: 1. NO 2 2. NH 3 3. OH A. Remove H + to write the conjugate base: 1. HBr Br 2. H 2 S HS 3. H 2 CO 3 HCO 3 B. Add H + to write the conjugate acid: 1. NO 2 HNO 2 2. NH 3 NH OH H 2 O Identify the sets that contain acidbase conjugate pairs. 1. HNO 2, NO 2 2. H 2 CO 3, CO HCl, ClO 4 4. HS, H 2 S 5. NH 3, NH HNO 2, NO 2 4. HS, H 2 S 5. NH 3, NH

5 A. The conjugate base of HCO 3 is 1. CO HCO 3 3. H 2 CO 3 B. The conjugate acid of HCO 3 is 1. CO HCO 3 3. H 2 CO 3 C. The conjugate base of H 2 O is 1. OH 2. H 2 O 3. H 3 O + D. The conjugate acid of H 2 O is 1. OH 2. H 2 O 3. H 3 O + A. The conjugate base of HCO 3 is 1. CO 3 2 B. The conjugate acid of HCO 3 is 3. H 2 CO 3 C. The conjugate base of H 2 O is 1. OH D. The conjugate acid of H 2 O is 3. H 3 O Chapter 10 Acids and Bases Strengths of Acids 10.3 Strengths of Acids and Bases Strong acids completely ionizes (100%) in aqueous solutions. HCl(g) + H 2 O(l) H 3 O + (aq) + Cl (aq) Weak acids dissociate only slightly in water to form a solution of mostly molecules and a few ions. H 2 CO 3 (aq) + H 2 O(l) H 3 O + (aq) + HCO 3 (aq) Strong Acids A strong acid dissolved in water Dissociates into ions. Gives H 3 O + and the anion (A ). Weak Acids Weak acids dissolved in water, Dissociate only a few molecules. Remain mostly as the undissociated (molecular) form. Have low concentrations of H 3 O + and anion (A ). HA(aq) + H 2 O(l) H 3 O + (aq) + A (aq)

6 Comparing Strong and Weak Acids In solution, HCl, a strong acid, dissociates 100%. acetic acid, CH 3 COOH a weak acid, is mostly molecules and only a few ions. Strong Acids Strong acids Make up six of all the acids. Have weak conjugate bases Weak Acids Strong Bases Weak acids Make up most of the acids. Have strong conjugate bases. Strong bases Are formed from metals of Groups 1A(1) and 2A(2). Include LiOH, NaOH, KOH, and Ca(OH) 2. Dissociate completely in water. KOH(s) K + (aq) + OH (aq) Weak Bases Weak bases Are most other bases. Dissociate only slightly in water. Form only a few ions in water. NH 3 (g) + H 2 O(l) NH 4+ (aq) + OH (aq) Identify each of the following as a strong or weak acid or base. A. HBr B. HNO 2 C. NaOH D. H 2 SO 4 E. Cu(OH)

7 A. HBr strong acid B. HNO 2 weak acid C. NaOH strong base D. H 2 SO 4 strong acid E. Cu(OH) 2 weak base Identify the stronger acid in each pair. 1. HNO 2 or H 2 S 2. HCO 3 or HBr 3. H 3 PO 4 or H 3 O Acid Dissociation Constant Identify the stronger acid in each pair. 1. HNO 2 2. HBr 3. H 3 O + 39 In a weak acid, the rate of the dissociation of the acid is equal to the rate of the association. HA + H 2 O H 3 O + + A The equilibrium expression is K eq = [H 3 O + ][A ] [HA][H 2 O] Because the concentration of H 2 O is constant, the K a expression for a weak acid is K a = [H 3 O + ][A ] [HA] 40 Acid Characteristics and K a Some Acid Dissociation Constants TABLE 10.5 K a values for some weak acids are shown in Table TABLE 10.4 Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

8 Writing K a for a Weak Acid Write the K a for H 2 S. 1. Write the equation for the dissociation of H 2 S. H 2 S(aq) + H 2 O(l) H 3 O + (aq) + HS (aq) Write the K a for HCN. 2. Set up the K a expression K a = [H 3 O + ][HS ] [H 2 S] Chapter 10 Acids and Bases 1. Write the equation for the dissociation of HCN. HCN (aq)+ H 2 O(l) H 3 O + (aq) + CN (aq) 10.4 Ionization of Water 2. Set up the K a expression K a = [H 3 O + ][CN ] [HCN] Note: K a = K eq [H 2 O] Ionization of Water Pure Water is Neutral In the ionization of water, H + is transferred from one H 2 O molecule to another. One water molecule acts as an acid, while another acts as a base. H 2 O + H 2 O H 3 O + + OH H:O: + H:O: H:O:H + + :O:H H H H water water hydronium hydroxide ion (+) ion () 47 In pure water, The ionization of water molecules produces small, but equal quantities of H 3 O + and OH ions. Molar concentrations are indicated in brackets as [H 3 O + ] and [OH ]. [H 3 O + ] = 1.0 x 10 7 M [OH ] = 1.0 x 10 7 M 48 8

9 Acidic s Adding an acid to pure water Increases the [H 3 O + ]. Increases the [H 3 O + ] to more than 1.0 x 10 7 M. Decreases the [OH ]. Basic s Adding a base to pure water, Increases the [OH ]. Causes the [OH ] to exceed 1.0 x 10 7 M. Decreases the [H 3 O + ] Comparison of [H 3 O + ] and [OH ] Ion Product of Water, K w The ion product constant, K w, for water Is the product of the concentrations of the hydronium and hydroxide ions. K w = [ H 3 O + ] [ OH ] Can be obtained from the concentrations in pure water. K w = [ H 3 O + ] X [ OH ] K w = [1.0 x 10 7 M] X [ 1.0 x 10 7 M] = 1.0 x [H 3 O + ] and [OH ] in s Guide to Calculating [H 3 O + ] In neutral, acidic, or basic solutions, the K w is always 1.0 x TABLE

10 Calculating [H 3 O + ] What is the [H 3 O + ] of a solution if [OH ] is 5.0 x 10 8 M? STEP 1 Write the K w for water. K w = [H 3 O + ][OH ] = 1.0 x STEP 2 Rearrange the K w expression. [H 3 O + ] = 1.0 x [OH ] If lemon juice has [H 3 O + ] of 2 x 10 3 M, what is the [OH ] of the solution? 1) 2 x M 2) 5 x M 3) 5 x M STEP 3 Substitute [OH ]. [H 3 O + ] = 1.0 x = 2.0 x 10 7 M 5.0 x ) 5 x M Rearrange the K w to solve for [OH ] K w = [H 3 O + ][OH ] = 1.0 x [OH ] = 1.0 x = 5 x M 2 x 10 3 The [OH ] of an ammonia solution is 4.0 x 10 2 M. What is the [H 3 O + ] of the solution? 1) 2.5 x M 2) 2.5 x M 3) 2.5 x M ) 2.5 x M [ H 3 O + ] = 1.0 x = 2.5 x M 4.0 x