1 Chapter 8 Acids and Bases

2 What is an Acid? In water, an acid increases the hydronium (H 3 O + ) concentration of an aqueous solution. Strong acids ionizes essentially completely in water. Weak acids only partially ionize in water.

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4 Molarity and Acid Concentration Molarity Molarity is defined as the number of moles of solute per liter of solution. M M = 3.0 M A solution that contains 6.0 moles of HCl in 2.00 liters of solution is a 3.0 M HCl solution.

5 Example: Example: Molarity and Acid Concentration What is the molarity of a solution of 56.8 grams of nitric acid, HNO 3 (molar mass = g/mol), dissolved in enough water to make mL of solution? M M =

6 Solution: Solution: Molarity and Acid Concentration What is the molarity of a solution of 56.8 grams of nitric acid, HNO 3 (molar mass = g/mol), dissolved in enough water to make mL of solution? M 1.81 M M = = 1.81 M

7 What is a Base? In water, an base is a substance that can accept hydrogen ion, H +. Many do this by releasing OH – ions. Strong bases combine essentially completely with H +. Weak bases are considerably less reactive.

8 Oxide Reactions with Water Group 1a and 2a metal oxides react with water to form basic solutions. Non-metal oxides react with water to form acidic solutions. CaO(s) + H 2 O(l) → Ca(OH) 2 (aq) SO 3 (g) + H 2 O(l) → H 2 SO 4 (aq)

9 The pH Scale pH  -log [H + ] If [H + ] = 1.00 x 10 –6 M, then pH =6.00 pH = -log [1.00 x 10 –6 ] = 6.00 If [H + ] = 8.56 x 10 –12 M, then pH =11.07 pH = -log [8.56 x 10 –12 ] = 11.07

10 Exercise: Exercise: The pH Scale Calculate the pH of a solution with [H + ] = 9.22 x 10 –8 M

11 Solution: Solution: The pH Scale Calculate the pH of a solution with [H + ] = 9.22 x 10 –8 M pH =7.04 pH = -log [9.22 x 10 –8 M] = 7.04

12 Exercise: Exercise: [H + ] from pH Calculate the [H + ] of a solution of pH [H + ] = 10 –pH

13 Solution: Solution: [H + ] from pH Calculate the [H + ] of a solution of pH [H + ] = 10 –pH [H + ] = 10 –2.39 [H + ] =4.1 x 10 –3 M

14 Relationship of [H + ] to [OH – ]

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16 Visual Representation of Table 8.6 data

17 Sample Neutralization Reactions H 3 O + + OH – → 2H 2 O HCl + NaOH → NaCl + H 2 O acid base salt water CaCO 3 (s) + 2CH 3 COOH(aq) → Ca 2+ (aq) + CO 2 (g) + H 2 O(l) + 2CH 3 COO – (aq)