CHEM 1120 1st Edition Lecture 13 Outline of Last Lecture I Bronsted Lowry Acids and Bases II Autoionization of Water III pH Scale Outline of Current Lecture I Strong Weak Acids and Bases II Solving Quadratic Equilibrium Equations III Polyprotic Acids Current Lecture I Keep in mind that water can be an acid In an acidic solution H OH In a basic solution OH H In a neutral solution H OH Strong Acids HCl H2SO4 HBr HI HNO3 HClO3 HClO4 These are by definition strong electrolytes and exist totally ionized in aqueous solutions For monoprotic strong acids H3O acid Strong Bases Soluble hydroxides alkali metals and heavier alkali earth metal hydroxides Ca2 Sr2 and Ba2 These also dissociate completely in aqueous solutions These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Most acids are weak acids so memorizing the strong acids would benefit the most Ka is a measure of acid strength the smaller the Ka the weaker the acid and vice versa For all the strong acids the Ka is greater than 1 Use ICE tables and approximations to simplify problems Don t confuse strength quantity and concentration Strength strong weak Quantity much little Concentration concentrated dilute For a generalized acid dissociation and the equilibrium expression would be Example Calculate the concentrations of HNO2 H and NO2 in 0 2 M HNO2 II How do we solve the previous algebraic equation Option 1 is use a graphing calculator but this is not allowed on the test Option 2 is use the quadratic formula Option 3 is the approximation method We assume that x is negligible compared to the other concentrations so therefore 0 2 x is equal to 0 2 In order to test the validity of the approximation we use the 5 test You would place x over the concentration 0 2 and multiply by 100 If this ends up being under 5 then it passes and we can use it III Polyprotic acids contain more than one mole of ionizable hydronium ions per mole of acid An example of this is oxalic acid Example Calculate the concentrations of all the species in 0 2 M H2SO4 Ka 1 3 X 10 2 Kb 6 3 X 10 8
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