Lecture Presentation Lecture Presentation Chapter 4 Reactions in Aqueous Solution 2012 Pearson Education Inc 2012 Pearson Education Inc John D Bookstaver St Charles Community College Cottleville MO Solutions Solutions are defined as homogeneous mixtures of two or more pure substances The solvent is present in greatest abundance All other substances are solutes 2012 Pearson Education Inc Aqueous Reactions Dissociation When an ionic substance dissolves in water the solvent pulls the individual ions from the crystal and solvates them This process is called dissociation 2012 Pearson Education Inc Aqueous Reactions Dissociation An electrolyte is a substances that dissociates into ions when dissolved in water 2012 Pearson Education Inc Aqueous Reactions Solutions An electrolyte is a substance that dissociates into ions when dissolved in water A nonelectrolyte may dissolve in water but it does not dissociate into ions when it does so 2012 Pearson Education Inc Aqueous Reactions Electrolytes and Nonelectrolytes Soluble ionic compounds tend to be electrolytes 2012 Pearson Education Inc Aqueous Reactions Electrolytes and Nonelectrolytes Molecular compounds tend to be nonelectrolytes except for acids and bases 2012 Pearson Education Inc Aqueous Reactions Electrolytes A strong electrolyte dissociates completely when dissolved in water A weak electrolyte only dissociates partially when dissolved in water 2012 Pearson Education Inc Aqueous Reactions Strong Electrolytes Are Strong acids Strong bases 2012 Pearson Education Inc Aqueous Reactions Strong Electrolytes Are Strong acids Strong bases Soluble ionic salts 2012 Pearson Education Inc Aqueous Reactions Precipitation Reactions When one mixes ions that form compounds that are insoluble as could be predicted by the solubility guidelines a precipitate is formed 2012 Pearson Education Inc Aqueous Reactions Metathesis Exchange Reactions Metathesis comes from a Greek word that means to transpose AgNO3 aq KCl aq AgCl s KNO3 aq 2012 Pearson Education Inc Aqueous Reactions Metathesis Exchange Reactions Metathesis comes from a Greek word that means to transpose It appears as though the ions in the reactant compounds exchange or transpose ions AgNO3 aq KCl aq AgCl s KNO3 aq 2012 Pearson Education Inc Aqueous Reactions Solution Chemistry It is helpful to pay attention to exactly what species are present in a reaction mixture i e solid liquid gas aqueous solution If we are to understand reactivity we must be aware of just what is changing during the course of a reaction 2012 Pearson Education Inc Aqueous Reactions Molecular Equation The molecular equation lists the reactants and products in their molecular form AgNO3 aq KCl aq AgCl s KNO3 aq 2012 Pearson Education Inc Aqueous Reactions Ionic Equation In the ionic equation all strong electrolytes strong acids strong bases and soluble ionic salts are dissociated into their ions This more accurately reflects the species that are found in the reaction mixture Ag aq NO3 aq K aq Cl aq AgCl s K aq NO3 aq 2012 Pearson Education Inc Aqueous Reactions Net Ionic Equation To form the net ionic equation cross out anything that does not change from the left side of the equation to the right Ag aq NO3 aq K aq Cl aq AgCl s K aq NO3 aq 2012 Pearson Education Inc Aqueous Reactions Net Ionic Equation To form the net ionic equation cross out anything that does not change from the left side of the equation to the right The only things left in the equation are those things that change i e react during the course of the reaction Ag aq Cl aq AgCl s 2012 Pearson Education Inc Aqueous Reactions Net Ionic Equation To form the net ionic equation cross out anything that does not change from the left side of the equation to the right The only things left in the equation are those things that change i e react during the course of the reaction Those things that didn t change and were deleted from the net ionic equation are called spectator ions Ag aq NO3 aq K aq Cl aq AgCl s K aq NO3 aq 2012 Pearson Education Inc Aqueous Reactions Writing Net Ionic Equations 1 Write a balanced molecular equation 2 Dissociate all strong electrolytes 3 Cross out anything that remains unchanged from the left side to the right side of the equation 4 Write the net ionic equation with the species that remain 2012 Pearson Education Inc Aqueous Reactions Acids The Swedish physicist and chemist S A Arrhenius defined acids as substances that increase the concentration of H when dissolved in water Both the Danish chemist J N Br nsted and the British chemist T M Lowry defined them as proton donors Aqueous Reactions 2012 Pearson Education Inc Acids There are only seven strong acids Hydrochloric HCl Hydrobromic HBr Hydroiodic HI Nitric HNO3 Sulfuric H2SO4 Chloric HClO3 Perchloric HClO4 2012 Pearson Education Inc Aqueous Reactions Bases Arrhenius defined bases as substances that increase the concentration of OH when dissolved in water Br nsted and Lowry defined them as proton acceptors 2012 Pearson Education Inc Aqueous Reactions Bases The strong bases are the soluble metal salts of hydroxide ion Alkali metals Calcium Strontium Barium 2012 Pearson Education Inc Aqueous Reactions Acid Base Reactions In an acid base reaction the acid donates a proton H to the base 2012 Pearson Education Inc Aqueous Reactions Neutralization Reactions Generally when solutions of an acid and a base are combined the products are a salt and water CH3COOH aq NaOH aq CH3COONa aq H2O l 2012 Pearson Education Inc Aqueous Reactions Neutralization Reactions When a strong acid reacts with a strong base the net ionic equation is HCl aq NaOH aq NaCl aq H2O l 2012 Pearson Education Inc Aqueous Reactions Neutralization Reactions When a strong acid reacts with a strong base the net ionic equation is HCl aq NaOH aq NaCl aq H2O l H aq Cl aq Na aq OH aq Na aq Cl aq H2O l 2012 Pearson Education Inc Aqueous Reactions Neutralization Reactions When a strong acid reacts with a strong base the net ionic equation is HCl aq NaOH aq NaCl aq H2O l H aq Cl aq Na aq OH aq Na aq Cl aq H2O l H aq OH aq H2O l 2012 Pearson Education Inc Aqueous Reactions Gas Forming Reactions Some metathesis reactions do not give the product expected In this reaction the expected product H2CO3 decomposes to give a gaseous product CO2 CaCO3 s HCl aq CaCl2 aq CO2 g H2O l 2012 Pearson Education Inc Aqueous Reactions Gas Forming Reactions When a carbonate or bicarbonate reacts with an acid the products are a salt carbon dioxide and water