Predicting Ionic Solubility

Predicting Ionic Solubility Precipitation Formation

Predicting Ionic Solubility • Most Ionic compounds (Salts) are soluble in water, but the degree of solubility is different for different salts. Salts can be described in one of the following categories: • Soluble • Partly (or Sparingly) Soluble • Insoluble

Predicting Ionic Solubility • A soluble salt can be defined in 2 ways: • Qualitatively: • Soluble salts tend to dissolve in aqueous solution in almost unlimited amounts. • Quantitatively: • More than 1 g of the salt dissolves in 100 mL of solution. • or More than 0.1 mole of the salt will dissolve in 1 L of solution.

Predicting Ionic Solubility • A partly soluble salt can be defined in 2 ways: • Qualitatively: • Partly soluble salts tend to dissolve in aqueous solution but in limited amounts. • Quantitatively: • Between 1 g and 0.1g of the salt dissolves in 100 mL of solution. • Between 0.1mole and 0.01 mole of the salt will dissolve in 1 L of solution.

Predicting Ionic Solubility • An insoluble salt can be defined in 2 ways: • Qualitatively: • Insoluble salts do not dissolve in aqueous solution in any amount. • Quantitatively: • Less than 0.1g of the salt dissolves in 100 mL of solution. • Less than 0.01 mole of the salt will dissolve in 1 L of solution.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • if the combination of Ca2+ and CO32- forms a precipitate, the chart will indicate it is insoluble or has low solubility. • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • if the combination of Ca2+ and CO32- forms a precipitate, the chart will indicate it is insoluble or has low solubility. • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • if the combination of Ca2+ and CO32- forms a precipitate, the chart will indicate it is insoluble or has low solubility. • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • is the combination of Ca2+ and CO32- in the soluble group? • is the combination of Ca2+ and CO32- in the insoluble group? • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • is the combination of Ca2+ and CO32- in the soluble group? NO • is the combination of Ca2+ and CO32- in the insoluble group? • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • is the combination of Ca2+ and CO32- in the soluble group? • is the combination of Ca2+ and CO32- in the insoluble group? • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • is the combination of Ca2+ and CO32- in the soluble group? • is the combination of Ca2+ and CO32- in the insoluble group? YES • if the combination of Ca2+ and CO32- doesn’tform a precipitate, the chart will indicate it is soluble.

Predicting Solubility - Using the Solubility Chart • Using the Solubility Chart, a guided example. Example: Is Calcium carbonate soluble or insoluble? • Determine the ions present in this compound: - Ca2+ and CO32- 2. Look up the anion on the Solubility chart. (in this case CO32-) • Look for the cation (in this case Ca2+) in the two lists: • is the combination of Ca2+ and CO32- in the soluble group? • is the combination of Ca2+ and CO32- in the insoluble group? • The combination of Ca2+ and CO32- forms a precipitate, the chart indicates it has Low Solubility

Predicting Ionic Solubility • Use a solubility chart to predict the solubility of the following compounds in water. State whether they are soluble or insoluble in water.

General Solubility Rules (Time savers) • Nitrates (NO31-) • soluble with all cations. • Ammonium (NH41+) • soluble with all anions. • Alkali Metals (Li1+, Na1+, K1+,…) • soluble with all anions.

Predicting the Precipitate that Forms in a Chemical Reaction • In a chemical reaction between two Ionic solutions, a precipitatemay form. • If a precipitate forms, one of the products of the reaction is the precipitate, in other words, it is insoluble and it is asolid. • We can predict which product forms the precipitate if we have a solubility chart handy.

Predicting the Precipitate that Forms in a Chemical Reaction • For example, • When a solution of Potassium iodide [KI (aq)] reacts with a solution of Lead (II) nitrate [Pb(NO3)2 (aq)], a yellow precipitate forms. • This reaction can be described in words: • Potassium iodide solution reacts with Lead (II) nitrate solution to form Potassium nitrate with Lead (II) iodide. • One of the products is insoluble (the yellow precipitate)

Predicting the Precipitate that Forms in a Chemical Reaction • First Step: Write out the Balanced Reaction Equation: 2KI (aq) + 1Pb(NO3)2(aq) 2KNO3(?) + 1PbI2(?) • Second step: Determine which product is insoluble:

Predicting the Precipitate that Forms in a Chemical Reaction • The Total Ionic Equation shows all of the ions present in the two solutions, and which ones form the precipitate. When writing this equation, you must balance the atoms and the charges, you must also indicate which species are (aq) and which, if any forms the precipitate (s). 2K1+(aq) + 2I1-(aq)

Predicting the Precipitate that Forms in a Chemical Reaction • The Total Ionic Equation shows all of the ions present in the two solutions, and which ones form the precipitate. When writing this equation, you must balance the atoms and the charges, you must also indicate which species are (aq) and which, if any forms the precipitate (s). 2K1+(aq) + 2I1-(aq) + 1Pb2+(aq) + 2NO31-(aq)

Predicting the Precipitate that Forms in a Chemical Reaction • The Total Ionic Equation shows all of the ions present in the two solutions, and which ones form the precipitate. When writing this equation, you must balance the atoms and the charges, you must also indicate which species are (aq) and which, if any forms the precipitate (s). 2K1+(aq) + 2I1-(aq) + 1Pb2+(aq) + 2NO31-(aq) 2K1+(aq) + 2NO31-(aq)

Predicting the Precipitate that Forms in a Chemical Reaction • The Total Ionic Equation shows all of the ions present in the two solutions, and which ones form the precipitate. When writing this equation, you must balance the atoms and the charges, you must also indicate which species are (aq) and which, if any forms the precipitate (s). 2K1+(aq) + 2I1-(aq) + 1Pb2+(aq) + 2NO31-(aq) 2K1+(aq) + 2NO31-(aq) + 1PbI2(s)

Predicting the Precipitate that Forms in a Chemical Reaction • The Net Ionic Equation demonstrates only the ions that form the precipitate. To show the Net Ionic Equation, you get rid of Spectator Ions – ions that do not take part in the reaction (ie., they appear the same on the reactant side as they do on the product side.) 2K1+(aq) + 2I1-(aq) + 1Pb2+(aq) + 2NO31-(aq) 2K1+(aq) + 2NO31-(aq) + 1PbI2(s)

Predicting the Precipitate that Forms in a Chemical Reaction • The Net Ionic Equation demonstrates only the ions that form the precipitate. To show the Net Ionic Equation, you get rid of Spectator Ions – ions that do not take part in the reaction (ie., they appear the same on the reactant side as they do on the product side.) 2K1+(aq) + 2I1-(aq) + 1Pb2+(aq) + 2NO31-(aq) 2K1+(aq)+ 2NO31-(aq) + 1PbI2(s)

Predicting the Precipitate that Forms in a Chemical Reaction • The Net Ionic Equation demonstrates only the ions that form the precipitate. To show the Net Ionic Equation, you get rid of Spectator Ions – ions that do not take part in the reaction (ie., they appear the same on the reactant side as they do on the product side.) 2K1+(aq)+ 2I1-(aq) + 1Pb2+(aq)+ 2NO31-(aq) 2K1+(aq)+ 2NO31-(aq) + 1PbI2(s)

Predicting the Precipitate that Forms in a Chemical Reaction • The Net Ionic Equation demonstrates only the ions that form the precipitate. To show the Net Ionic Equation, you get rid of Spectator Ions – ions thatdo not take part in the reaction (ie., they appear the same on the reactant side as they do on the product side.) Simplified and rearranged: 1Pb2+(aq) + 2I1-(aq) 1PbI2(s)

Summary - Big Ideas • Some double displacement reactions form precipitates. • Precipitates form in double displacement reactions between two ionic solutions. • Precipitates are insoluble ionic compounds, and do not dissolve. • A net ionic equation demonstrates only the ions that react.

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Predicting Ionic Solubility