Exam 2 Study Guide October 15 2014 1 Chapter 4 Reactions in Aqueous Solution a Precipitation Reactions i Solubility of Ionic Compounds 1 2 forces come into play when ionic solid dissolves in water a The attractive forces between the oppositely charges ions making up the solid b The attractive forces between water and the ions 2 The extent to which a solution occurs depends on a balance of these forces a The force of attraction between water molecules and the ions of the solid which tend to bring the solid into solution if this predominates compound is soluble in water b The force of attraction between oppositely charged ions which tends to keep them in the solid state if this is the main factor expect water solubility to be low 3 Can t determine the strength of these 2 forces for a given solid in advance use the solubility chart a Choose the cation row and read across for the anion column i White block no precipitate will form ii Green block precipitate will form from dilute solution 4 When water solutions of 2 different ionic compounds are mixed insoluble solid separates out of solution a This is the precipitate it is ionic itself ii Net Ionic Equations 1 To find the net ionic equation a Find the total ionic equation by adding all of the reactants and b Cancel out the ions that appear on both sides of the equation 2 Net equations equations that exclude ions that don t take part in the a Atom balance must be same number of atoms of each element on products reaction both sides b Charge balance there must be the same total charge on both sides 3 Used for precipitation in this chapter but they have a wide range of functions iii Stoichiometry 1 b Acid Base Reactions Introduction i 1 Acidic solutions have a sour taste and affect the color of certain dyes a Litmus turns blue red in acidic solution vice versa in basic solution 2 Basic solutions have slippery feeling and change color of indicator 3 An acid is a species that produces H ions in water solution 4 A base is a species that produces OH ions in water solution ii Strong and Weak Acids and Bases 1 Strong acid ionize completely forming H ions and anions a Ex HCL H Cl 2 Weak acid molecules containing an ionizable hydrogen atom a Ex HB H B b The double arrow means that the reaction doesn t go to completion mixture is formed containing significant amounts of both products and reactants 3 Strong Base in water solution completely ionized to OH ions and cations a Ex NaOH Na OH 4 Weak base produce OH ions through reacting with water molecules acquiring H ions and leaving OH ions behind a Ex NH3 H20 NH4 OH b Common class of weak bases is made up of organic molecules known as amines derivatives of ammonia in which one or more hydrogen atom has been replaced by hydrocarbon groups i Ex methylamine hydrogen atom is replaced by a CH3 group 1 CH3NH2 H2O CH3NH3 OH 5 Strong acids and bases are strong electrolytes because they completely ionize in water a Hydrofluoric acid and ammonia are known as weak electrolytes because they are poor conductors because water solution contains few ions Strong Acid Name of Acid Strong Base Name of Base HCl HBr HI HNO3 HClO4 H2SO4 Hydrochloric acid Hydrobromic acid Hydriodic acid LiOH NaOH KOH Nitric acid Ca OH 2 Perchloric acid Sr OH 2 Sulfuric acid Ba OH 2 Lithium hydroxide Sodium hydroxide Potassium hydroxide Calcium hydroxide Strontium hydroxide Barium hydroxide iii Equations for Acid Base Reactions 1 Strong acid strong base a The strong acid is completely converted to H and ions b The strong base is completely converted to OH and ions c Neutralization reaction when the solutions are mixed the H and the OH react with each other to form water d Net ionic equation i H aq OH aq H2O e The other ions in the reaction don t show up in the net ionic equation because they are spectator ions and don t react 2 Weak acid strong base a When strong base is added to a solution 2 step reaction occurs Ionization of weak acid to the 2 independent ions i ii Neutralization of the H ions produced in the first step by the OH ions of the base solution b General equation i HA aq OH aq H2O A ii The A is a spectator ion 3 Strong acid weak base a Another 2 step reaction in example of HCl reacting with NH3 i Reaction of NH3 with H2O to form NH4 and OH ions 1 NH3 H2O NH4 OH ii The H ions of the strong acid neutralize the OH ions formed iii Overall equation is from canceling the hydroxide ions and in the first step 1 H OH H2O water that occur on both sides 1 H NH3 NH4 b General equation i H A HA iv Acid Base Titrations 1 Acid base reactions in water solution are commonly used to determine the concentration of a dissolved species or its percentage in a solid mixture a Done by using a titration measuring the volume or a standard solution a solution of known concentration required to react with a measured amount of sample b Objective of a titration is to determine the equivalence point the point at which reaction is complete i In the example of titrating acetic acid the equivalence point is when the number of moles of OH added is exactly equal to the number of moles of acetic acid originally present 1 This is determined by adding a drop of acid base indicator ex Phenolphthalein which will change color at equivalence point c Oxidation Reduction Reactions i Introduction 1 Redox reaction the transfer of electrons between 2 species a One species will lose electrons oxidized b The other will gain electrons reduced GER Become more LEO Become more 2 Oxidation and reduction occur together in the same reaction can t have one 3 There is no net change in the number of electrons in a redox reaction without the other ii Oxidation number 1 Oxidation number rules a The oxidation number of an element in an elementary substance 0 b The oxidation number of an element in a monoatomic ion is equal to i Cl2 0 the charge of that ion i Cl 1 2 Definitions c Certain elements have the same oxidation number in all their compounds i Group 1 elements always have an oxidation number of 1 ii Group 2 elements always have an oxidation number of 2 iii Fluorine always has an oxidation number of 1 d Hydrogen in a compound has an oxidation number of 1 unless it is combined with a metal in which it is 1 i HCl 1 NaH 1 e The sum of the oxidation numbers in a neutral species is 0 and in a polyatomic ion is equal to the charge of the ion f Oxygen in a compound has an oxidation number of 2 unless it is combined with …