Ba(OH) 2. 8H 2 O + 2NH 4 SCN  Ba(SCN) 2 + 2NH H 2 O What is the sign of  G in this reaction? What is the sign of  G in this reaction? What is the sign of  H in this reaction? What is the sign of  H in this reaction? What is the driving force in this reaction? What is the driving force in this reaction? How does the reaction proceed even though both reactants are solids? How does the reaction proceed even though both reactants are solids?

Ba(OH) 2. 8H 2 O + 2NH 4 SCN  Ba(SCN) 2 + 2NH H 2 O If the temperature is raised, which direction will equilibrium shift toward? If the temperature is raised, which direction will equilibrium shift toward? If the temperature is lowered? If the temperature is lowered? If the temperature of an exothermic reaction is raised? If the temperature of an exothermic reaction is raised? If the temperature of an exothermic reaction is lowered? If the temperature of an exothermic reaction is lowered?

Why can we ignore the concentration ratio of solvent (usually water) in equilibrium expressions? (Hint: consider the case of the dissociation of 0.1M acetic acid if you would like a concrete example.) Why can we ignore the concentration ratio of solvent (usually water) in equilibrium expressions? (Hint: consider the case of the dissociation of 0.1M acetic acid if you would like a concrete example.) Why is it also permissible to omit the concentration of solids in equilibrium expressions? (If you want a concrete example use Mn, the density of Mn is 7.21g/mL.) Why is it also permissible to omit the concentration of solids in equilibrium expressions? (If you want a concrete example use Mn, the density of Mn is 7.21g/mL.)

Steps in Experimental Design 5. Collect data 6. Evaluate data Does it support the hypothesis? Do additional experiments need to be done?

Steps in Experimental Design 1. Formulate the question 2. Develop the hypothesis Hypothesis must be testable 3. Make predictions What will the data look like if the hypothesis is supported? Not supported? 4. Plan methods for testing hypothesis What experimental methods will be used for testing the hypothesis?

Hypotheses Study of the effectiveness of laundry detergents Study of the effectiveness of laundry detergents Taking aspirin reduces the length of headache time versus taking Tylenol Taking aspirin reduces the length of headache time versus taking Tylenol Lightbulbs: longevity vs. cost Lightbulbs: longevity vs. cost Application of fertilizer increases the concentration of nitrate in nearby surface water Application of fertilizer increases the concentration of nitrate in nearby surface water Null hypothesis: Increasing the size of the buffer zone between a farm field and surface water does not result in reduced nutrient levels. Null hypothesis: Increasing the size of the buffer zone between a farm field and surface water does not result in reduced nutrient levels.

Solubility Product Example Calculate the solubility product of Ag 3 PO 4 if 500.mL of saturated solution contains g of dissolved salt. Neglect any hydrolysis effects. Calculate the solubility product of Ag 3 PO 4 if 500.mL of saturated solution contains g of dissolved salt. Neglect any hydrolysis effects.

Common Ion Effect Demo The solubility of KCl at room temperature is 3.7M The solubility of KCl at room temperature is 3.7M Each test tube contains 20mL of saturated KCl initially Each test tube contains 20mL of saturated KCl initially To test tube #1 20mL of 6M HCl is added To test tube #1 20mL of 6M HCl is added To test tube #2 20mL of 12M HCl is added To test tube #2 20mL of 12M HCl is added Explain results which appear to contradict the principles of the common ion effect. (Hint: Calculate the concentrations of K + and Cl - after the addition of HCl and calculate Q for each system.)

A waste bottle contains 0.01M Cu +1 and Sn +2 ions. For waste disposal, it is considerably cheaper if these two metals were precipitated separately rather than co-precipitated. Is such a separation possible? What would you precipitate the solutions with? (Use the K sp values given at the back of your book.) A waste bottle contains 0.01M Cu +1 and Sn +2 ions. For waste disposal, it is considerably cheaper if these two metals were precipitated separately rather than co-precipitated. Is such a separation possible? What would you precipitate the solutions with? (Use the K sp values given at the back of your book.)

Solubility Rules When applying solubility rules focus mainly on the anion portion of your molecule When applying solubility rules focus mainly on the anion portion of your molecule Always soluble: Always soluble: Group I metals and ammonium salts are soluble Group I metals and ammonium salts are soluble Nitrates, acetates, and perchlorates are soluble Nitrates, acetates, and perchlorates are soluble Cl -, Br -, and I - are soluble except with Ag +, Pb 2+, Cu +, and Hg 2+ Cl -, Br -, and I - are soluble except with Ag +, Pb 2+, Cu +, and Hg 2+ Sulfates are soluble except with Ca 2+, Sr 2+, Ba 2+, and Pb 2+ Sulfates are soluble except with Ca 2+, Sr 2+, Ba 2+, and Pb 2+ Always insoluble: Always insoluble: CO 3 2- are insoluble except with Group I and NH 4 + CO 3 2- are insoluble except with Group I and NH 4 + PO 4 3- are insoluble except with Group I and NH 4 + PO 4 3- are insoluble except with Group I and NH 4 + S 2- except Group I, II, and NH 4 + S 2- except Group I, II, and NH 4 + OH - except with Group I, NH 4 +, Ca 2+, Sr 2+, and Ba 2+ OH - except with Group I, NH 4 +, Ca 2+, Sr 2+, and Ba 2+

Acids and Bases Review Bronsted – Lowry Acid: Proton donor Bronsted – Lowry Acid: Proton donor Bronsted – Lowry Base: Proton acceptor Bronsted – Lowry Base: Proton acceptor Lewis acid: e- pair acceptor Lewis acid: e- pair acceptor Lewis base: e- pair donor Lewis base: e- pair donor Salt: ionic solid can be thought of as the product of an acid base reaction Salt: ionic solid can be thought of as the product of an acid base reaction

Demonstration: pH of distilled water Why is the pH of distilled water acidic? Write it down in your notebook. Why is the pH of distilled water acidic? Write it down in your notebook. How can this be minimized? How can this be minimized? How can the CO 2 be removed? How can the CO 2 be removed?

Strong acids & bases completely dissociate Strong Acids: Strong Acids: Everything else is weak Strong Bases: Alkali earth metal OH R4NOH R are all organic groups Alkaline earth metal OH (but not always soluble) Everything else is weak

Explain why, if benzoic acid is a weak acid with a K a of 6.28 x 10 -5, sodium benzoate is basic. Use equilibria. Explain why, if benzoic acid is a weak acid with a K a of 6.28 x 10 -5, sodium benzoate is basic. Use equilibria. If you have a 0.100M solution of sodium benzoate, what will be the pH of the solution? If you have a 0.100M solution of sodium benzoate, what will be the pH of the solution?

Buffers Buffer resists changes in pH Buffer resists changes in pH How does a buffer work? How does a buffer work? It contains significant amounts of both an acid and its conjugate base at equilibrium such that with the common ion effect/ L’Chatlier’s Principle it is able to minimize the effects of additions of acid or base It contains significant amounts of both an acid and its conjugate base at equilibrium such that with the common ion effect/ L’Chatlier’s Principle it is able to minimize the effects of additions of acid or base

Buffer Example What is the pH of mole of NaNO2 mixed with moles of HNO2 in 1.0 liter of solution? What is the pH of mole of NaNO2 mixed with moles of HNO2 in 1.0 liter of solution?

Buffer capacity How well a buffer resists changes to pH when a strong acid or strong base is added. How well a buffer resists changes to pH when a strong acid or strong base is added. Buffers are most effective closer to their pKa Buffers are most effective closer to their pKa Do not want to generally make a buffer more than 1 pH unit from its pKa Do not want to generally make a buffer more than 1 pH unit from its pKa

Buffer example 2 How would you make a buffer at a pH of 7.80? (There is more than one correct answer.) How would you make a buffer at a pH of 7.80? (There is more than one correct answer.)

Buffer example 3 What would the pH be of a buffer solution containing 100.0mL of 0.15M NH3 and 4.25mL of 1.0M HCl? What would the pH be of a buffer solution containing 100.0mL of 0.15M NH3 and 4.25mL of 1.0M HCl?

Buffer example 4 How will the pH change when 10.0mL of 0.1M HCl is added to a buffer containing 0.15moles of Sodium acetate and 0.12 moles of acetic acid in 1.0 liter of solution?