General Organic and Biological Chemistry Fourth Edition Karen

Solubility is the amount of solute that dissolves in a specific amount of solvent at a given temperature and is § affected by the type of solvent and temperature § expressed as grams of solute per 100 grams of solvent (usually water): © 2013 Pearson Education, Inc. Chapter 8 Section 3 2

Unsaturated Solutions Unsaturated solutions contain less than the maximum amount of solute. Dissolved solute

Saturated Solutions Saturated solutions contain the maximum amount of solute that can dissolve in the solvent. The rate at which the solute dissolves equals the rate at which the solute forms. © 2013 Pearson Education, Inc. Dissolved solute Undissolved solute Chapter 8 Section 3 4

Learning Check At 40 C, the solubility of KBr is 80 g/100 g of H 2 O. Identify the following solutions as either saturated (S) or unsaturated (U). Explain. 1. 200 g KBr is added to 200 g of water at 40 C. 2. 25 g KBr is added to 50 g of water at 40 C. © 2013 Pearson Education, Inc. Chapter 8 Section 3 5

Solution At 40 C, the solubility of KBr is 80 g/100 g of H 2 O. Identify the following solutions as either saturated (S) or unsaturated (U). Explain. 1. S 200 g KBr is added to 200 g of water at 40 C. This is the same as 100 g of KBr in 100 g of water, which is more than the solubility of 80 g of KBr/100 g of water at 40 C. 2. U 25 g KBr is added to 50 g of water at 40 C. This is the same as 50 g of KBr in 100 g of water, which is less than the solubility of 80 g of KBr/ 100 g of water at 40 C. © 2013 Pearson Education, Inc. Chapter 8 Section 3 6

Effect of Temperature on Solubility depends on temperature. The solubility § of most solids increases as temperature increases § of gases decreases as temperature increases © 2013 Pearson Education, Inc. Chapter 8 Section 3 7

Solubility and Pressure Henry’s law states that § the solubility of a gas in a liquid is directly related to the pressure of that gas above the liquid § at higher pressures, more gas molecules dissolve in the liquid © 2013 Pearson Education, Inc. Chapter 8 Section 3 8

Learning Check 1. Why could a bottle of carbonated drink possibly burst (explode) when it is left out in the hot sun? 2. Why do fish die in water that is too warm? © 2013 Pearson Education, Inc. Chapter 8 Section 3 9

Solution 1. Why could a bottle of carbonated drink possibly burst (explode) when it is left out in the hot sun? Gases become less soluble at high temperatures and leave the solution. As pressure inside the container increases, the bottle could burst. 2. Why do fish die in water that is too warm? Because O 2 gas is less soluble in warm water, fish cannot obtain enough O 2 to survive. © 2013 Pearson Education, Inc. Chapter 8 Section 3 10

Soluble and Insoluble Salts Ionic compounds that § dissolve in water are soluble salts § do not dissolve in water are insoluble salts Mixing certain aqueous solutions produces insoluble salts. © 2013 Pearson Education, Inc. Chapter 8 Section 3 11

Solubility Rules § Soluble salts typically contain at least one ion from Groups 1 A(1), NO 3−, NH 4+ or C 2 H 3 O 2− (acetate). § Most other combinations are insoluble. © 2013 Pearson Education, Inc. Chapter 8 Section 3 12

Using the Solubility Rules © 2013 Pearson Education, Inc. Chapter 8 Section 3 13

Learning Check Use the solubility rules to determine if each salt is soluble or insoluble. Explain. 1. 2. 3. 4. Na 2 SO 4 Mg. CO 3 Pb. Cl 2 Mg. Cl 2 © 2013 Pearson Education, Inc. Chapter 8 Section 3 14

Solution Use the solubility rules to determine if each salt is soluble or insoluble. Explain. 1. 2. 3. 4. Na 2 SO 4 Mg. CO 3 Pb. Cl 2 Mg. Cl 2 © 2013 Pearson Education, Inc. soluble; contains Na+ insoluble; contains carbonates insoluble; insoluble chloride soluble; only chlorides of Pb 2+, Ag+, and Hg 22+ are insoluble Chapter 8 Section 3 15

Formation of a Solid We can use solubility rules to predict whether a solid, called a precipitate, forms when two solutions of ionic compounds are mixed. Example: Ag. NO 3(aq) + Na. Cl(aq) © 2013 Pearson Education, Inc. Ag. Cl(s) + Na. NO 3(aq) Chapter 8 Section 3 16

Equations for Forming Solids A full equation shows the formulas of the compounds. An ionic equation shows the ions of the compounds. A net ionic equation shows only the ions that form a solid. © 2013 Pearson Education, Inc. Chapter 8 Section 3 17

Guide to Writing New Ionic Equations for an Insoluble Salt © 2013 Pearson Education,

Learning Check When solutions of Na 2 CO 3 and Ba(NO 3)2 are mixed,

Solution When solutions of Na 2 CO 3 and Ba(NO 3)2 are mixed, a white solid forms. Write the ionic and net ionic equations for the reaction. Step 1 Write the ions of the reactants. Ba 2+(aq) + 2 NO 3−(aq) 2 Na+(aq) © 2013 Pearson Education, Inc. + CO 32−(aq) Chapter 8 Section 3 20

Solution When solutions of Na 2 CO 3 and Ba(NO 3)2 are mixed, a white solid forms. Write the ionic and net ionic equations for the reaction. Step 2 Write the combinations of ions and determine if any are insoluble. © 2013 Pearson Education, Inc. Mixture Product Soluble 2 Na+(aq) + 2 NO 3−(aq) 2 Na. NO 3 (aq) yes Ba 2+(aq) + CO 32 -(aq) Ba. CO 3(s) no Chapter 8 Section 3 21

Solution When solutions of Na 2 CO 3 and Ba(NO 3)2 are mixed, a white solid forms. Write the ionic and net ionic equations for the reaction. Step 3 Write the ionic equation, including any insoluble salt as a solid. Step 4 Write the net ionic equation deleting spectator ions. © 2013 Pearson Education, Inc. Chapter 8 Section 3 22