General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 1 Chapter 8 Solutions 8.3 Solubility

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 2 Solubility is  the maximum amount of solute that dissolves in a specific amount of solvent  expressed as grams of solute in 100 grams of solvent (usually water): g of solute 100 g water Solubility

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 3 Unsaturated Solutions Unsaturated solutions  contain less than the maximum amount of solute  can dissolve more solute Dissolved solute

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 4 Saturated Solutions Saturated solutions contain  the maximum amount of solute that can dissolve  some undissolved solute at the bottom of the container Dissolved solute Undissolved solute

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 5 At 40  C, the solubility of KBr is 80 g/100 g of H 2 O. Identify the following solutions as either (S) saturated or (U) unsaturated. Explain. A. 60 g KBr added to 100 g of water at 40  C. B. 200 g KBr added to 200 g of water at 40  C. C. 25 g KBr added to 50 g of water at 40  C. Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 6 A. U 60 g of KBr/100 g of water is less than the solubility of 80 g of KBr/100 g of water. B. S 200 g KBr 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. C. U 25 g KBr 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. Solution

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. How to Read a Solubility Curve  On the line=saturated (full can not hold anymore solute)  Below the line=unsaturated (can hold more solute)  Above the line= supersaturated (holding more solute than it should, unstable condition) 7

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 8 Effect of Temperature on Solubility Solubility  depends on temperature  of most solids increases as temperature increases  of gases decreases as temperature increases

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 9 Soluble and Insoluble Salts Ionic compounds that  dissolve in water are soluble salts  do not dissolve in water are insoluble salts

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 10 Solubility Rules  Soluble salts typically contain at least one ion from Groups 1A(1), NO 3 −, or C 2 H 3 O 2 − (acetate).  Most other combinations are insoluble.

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 11 Examples of Using the Solubility Rules

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 12 Use the solubility rules to determine if each salt is (S) soluble or (I) insoluble. Explain. A. Na 2 SO 4 B. MgCO 3 C. PbCl 2 D. MgCl 2 Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 13 A. Na 2 SO 4 (S) soluble; contains Na + B. MgCO 3 (I) insoluble; contains carbonates C. PbCl 2 (I) insoluble; insoluble chloride D. MgCl 2 (S) soluble; only chlorides of Pb 2+, Ag +, and Hg 2 2+ are insoluble Solution

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 14 Formation of a Solid When solutions of salts are mixed, a solid forms if ions of an insoluble salt are present Example: AgNO 3 (aq) + NaCl(aq) AgCl(s) + NaNO 3 (aq)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 15 Equations for Forming Solids A full equation shows the formulas of the compounds. Pb(NO 3 )(aq) + 2NaCl(aq) PbCl 2 (s) + 2NaNO 3 (aq) An ionic equation shows the ions of the compounds. Pb 2+ (aq) + 2NO 3 − (aq) + 2Na + (aq) + 2Cl − (aq) PbCl 2 (s) + 2Na + (aq) + 2NO 3 − (aq) A net ionic equation shows only the ions that form a solid. Pb 2+ (aq) + 2Cl − (aq) PbCl 2 (s)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Guide to Writing New Ionic Equations for an Insoluble Salt 16

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 17 Finding the Insoluble Salt STEP 1 Write the ions of the reactants. Ba 2+ (aq) + 2NO 3 − (aq) + 2Na + (aq) + CO 3 2− (aq) STEP 2 Write the new combinations of the ions and determine if an insoluble salt forms. BaCO 3 (s) + 2Na + (aq) + 2NO 3 − (aq) STEP 3 Write the ionic equation, including the insoluble salt as a solid in the products. Ba 2+ (aq) + 2NO 3 − (aq) + 2Na + (aq) + CO 3 2 − (aq) BaCO 3 (s) + 2NO 3 − (aq) + 2Na + (aq) STEP 4 Write the net ionic equation deleting spectator ions. Ba 2+ (aq) + CO 3 2− (aq) BaCO 3 (s)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 18 Learning Check Write the formula of an insoluble salt, if any, and the net ionic equation for each of the following mixtures: A. BaCl 2 (aq) + Na 2 SO 4 (aq) ? B. AgNO 3 (aq) + KCl(aq) ? C. KNO 3 (aq) + NaCl(aq) ?

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 19 Solution A. BaCl 2 (aq) + Na 2 SO 4 (aq) ? BaSO 4 (s) Ba 2+ (aq) + SO 4 2− (aq) BaSO 4 (s) B. AgNO 3 (aq) + KCl(aq) ? AgCl(s) Ag + (aq) + Cl − (aq) AgCl(s) C. KNO 3 (aq) + NaCl(aq) ? None; all combinations of ions are soluble salts.