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Tro Chapter 16 - Aqueous Ionic Equilibria • Buffers • -

• Equilibria and the Solubility Product Constant, Ksp • Skip section 16.7 & 16.8

Suggested eoc problems: 33, 37, 41, 49, 53, 67, 71, 73, 87, 89, 91, 93, 101, 103

Tro 16.2 Calculating the pH of a buffer Buffers: that resist pH change Solution #1 : 0.500 M CH3COOH and 0.500 M CH3COONa; calculate pH

Calculate the pH following the addition of 0.02 mol of NaOH to 1.0 L of solution #1

Calculate the pH following the addition of 0.020 mol of HCl to 1.0 L of solution #1 Buffer’s continued Preparing a buffer from benzoic acid and sodium benzoate

An environmental chemist needs a buffer of pH 10.00 to study the effects of acid rain on limestone-rich How many grams of benzoic acid (C6H5COOH) should be added to 5.0 L of 0.050 M sodium benzoate . How many grams of Na2CO3 must she add to 1.5 L of (C H COONa) to make a pH 4.25 buffer? The K for freshly prepared 0.20 M NaHCO3 to make the buffer (Ka of 6 5 a - -11 benzoic acid is 6.3 x 10-5. HCO3 = 4.7 x 10 )

Tro 16.3 Buffer Effectiveness Tro 16.4 Acid-base titrations and pH curvers Reaction of a: 1) STRONG acid + STRONG base 2) STRONG base + weak acid 3) STRONG acid +

A/B titrations are used to determine Ka values for new - compounds and to quantitate and bases CH3COOH/CH3COO buffer with different ; chart shows how pH changes following addition of a given amount of strong base Strong Acid-Base Curve Weak Acid-Strong base titration curve

Calculate pH at 0 mL NaOH added 20 mL NaOH added 40 mL NaOH added 50 mL NaOH added

Weak Polyprotic Acid-Strong base titration curve Weak Base-Strong acid titration curve

Calculate pH at

0 mL HCl added – pH = 11.125

20 mL HCl added – pH = 9.25

40 mL HCl added – pH = 5.27

50 mL HCl added – pH = 1.95 Tro 16.5 Solubility equilibria Tro 16.5 Solubility equilibria and the solubility product constant Ksp

• Writing Ksp expressions • Calculating solubility • Factors affecting solubility

Problems involving sparingly soluble salts

Lead sulfate (PbSO4, MW 303.3) is a key component of lead-acid car batteries. Its solubility in water at 25˚C is -3 4.25 x 10 g/100 mL solution. What is the Ksp of PbSO4?

Calcium is major component of mortar,

plaster and cement, and solutions of Ca(OH)2 are used in industry as a cheap, strong base. Calculate the -6 solubility of Ca(OH)2 in water if the Ksp is 6.5 x 10 . Tro 16.6

Solubility and the common ion effect Precipitation and Qsp - the ion product

What is the solubility of Ca(OH)2 in 0.10 M -6 Ca(NO3)2? The Ksp for Ca(OH)2 is 6.5 x 10 . Will a precipitate form when 0.100 L of 0.30 M

Ca(NO3)2 is mixed with 0.200 L of 0.060 M NaF?

Would addition of H O+ affect the solubility of -11 3 Ksp for CaF2 = 3.2 x 10 a) Lead (II) bromide b) Copper (II) hydroxide c) Iron (II) sulfide