1. © 2009, Prentice-Hall, Inc. Acids Arrhenius defined acids as substances that increase the concentration of H + when dissolved in water. Brønsted and Lowry defined them as proton donors.

2. © 2009, Prentice-Hall, Inc. Bases Arrhenius defined bases as substances that increase the concentration of OH − when dissolved in water. Brønsted and Lowry defined them as proton acceptors.

3. © 2009, Prentice-Hall, Inc. Acid-Base Reactions In an acid-base reaction, the acid donates a proton (H + ) to the base.

4. © 2009, Prentice-Hall, Inc. Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H + ( aq ) + Cl - ( aq ) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l )

5. © 2009, Prentice-Hall, Inc. Neutralization Reactions When a strong acid reacts with a strong base, the net ionic equation is… HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H + ( aq ) + Cl - ( aq ) + Na + ( aq ) + OH - ( aq )  Na + ( aq ) + Cl - ( aq ) + H 2 O ( l ) H + (aq) + OH - (aq)  H 2 O (l)

6. Sample Exercise 4.7 Writing Chemical Equations for a Neutralization Reaction (a) Write a balanced molecular equation for the reaction between aqueous solutions of acetic acid (CH 3 COOH) and barium hydroxide, Ba(OH) 2. (b) Write the net ionic equation for this reaction. Solution Analyze: We are given the chemical formulas for an acid and a base and asked to write a balanced molecular equation and then a net ionic equation for their neutralization reaction. Plan: As Equation 4.12 and the italicized statement that follows it indicate, neutralization reactions form two products, H 2 O and a salt. We examine the cation of the base and the anion of the acid to determine the composition of the salt.

7. Sample Exercise 4.7 Writing Chemical Equations for a Neutralization Reaction Solution (continued) (b) To write the net ionic equation, we must determine whether each compound in aqueous solution is a strong electrolyte. CH 3 COOH is a weak electrolyte (weak acid), Ba(OH) 2 is a strong electrolyte, and Ba(CH 3 COO) 2 is also a strong electrolyte (ionic compound).

8. Sample Exercise 4.7 Writing Chemical Equations for a Neutralization Reaction (a)Write a balanced molecular equation for the reaction of carbonic acid (H 2 CO 3 ) and potassium hydroxide (KOH). (b) Write the net ionic equation for this reaction. Answers: (a) H 2 CO 3 (aq) + 2 KOH(aq) → 2 H 2 O(l) + K 2 CO 3 (aq); (b) H 2 CO 3 (aq) + 2 OH – (aq) → 2 H 2 O(l) + CO 3 2– (aq). (H 2 CO 3 is a weak acid and therefore a weak electrolyte, whereas KOH, a strong base, and K 2 CO 3, an ionic compound, are strong electrolytes.) Practice Exercise

9. © 2009, Prentice-Hall, Inc. Gas-Forming Reactions Some metathesis reactions do not give the product expected. In this reaction, the expected product (H 2 CO 3 ) decomposes to give a gaseous product (CO 2 ). CaCO 3 (s) + HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l)

10. © 2009, Prentice-Hall, Inc. Gas-Forming Reactions When a carbonate or bicarbonate reacts with an acid, the products are a salt, carbon dioxide, and water. CaCO 3 (s) + HCl (aq)  CaCl 2 (aq) + CO 2 (g) + H 2 O (l) NaHCO 3 (aq) + HBr (aq)  NaBr (aq) + CO 2 (g) + H 2 O (l)

11. © 2009, Prentice-Hall, Inc. Gas-Forming Reactions Similarly, when a sulfite reacts with an acid, the products are a salt, sulfur dioxide, and water. SrSO 3 (s) + 2 HI (aq)  SrI 2 (aq) + SO 2 (g) + H 2 O (l)