CH 302 1st Edition Lecture 11 Outline of Last Lecture I. Acids II. BasesIII. Strong Acids and Strong BasesIV. Weak Acids and Weak BasesOutline of Current Lecture I. Conjugate Acid Base PairsII. Acid/Base StrengthIII. Auto-ionization of waterIV. pH and pOHCurrent LectureConjugate Acid Base Pairs and Acid/Base Strength:- The strong an acid is, the weaker the conjugate base pair will be- The strong the base is, the weaker the conjugate acid base pair is- Acids: Donate protons- Bases: Accept protons- What is the conjugate base of HCOOH?o HCOO-- What is the conjugate acid of HPO4 2-?o H2PO4 –- What common features would help you identify these compounds as acids.o Most of these compounds have a COOH group and/or a very polar bond that includes a H atom such as H-Cl. There are 3 types of acids: oxy-acids (nitrous and nitric)o Carboxylic Acids: benzoic acid, acetic acid, formic acid Hydro acid: HCl, HCNWhat common features would help you identify these compounds as bases?- Many of them have hydroxyl groups or a nitrogen (N) with a lone pair.Please write the equation for the reaction that occurs when HClO2 is placed in water.- HClO2 + H2O � H3O+ + ClO2- Please write the equilibrium expression for HClO2.- [H O+ ][ClO − ] K=32- [HClO2]Please describe the concept of “acid strength”.- The stronger the acid, the more protons or H3O+ is in solution when a concentration of that acid is in solution. The more easily an acid is ionized or deprotonates, the strongerthe acid it is.- Are the acids listed in order of increasing acid strength or decreasing acid strength?- These acids are in order of DECREASING strengthPlease describe the concept of “base strength”?- The stronger the base, the more hydroxide ions or OH- is in solution when a concentrationof that base is in solution. The more easily an base is ionized or is protonated, the stronger the base it is.Are the bases listed in order of increasing base strength or decreasing base strength?- These bases are in order of DECREASING strengthCan you see a correlation between the list of acids and the list of bases? If yes, what is it?- Yes, the strongest acids (largest Ka’s) correlate with the weakest bases (smallest Kb’s). HClO2 is the strongest acid, but has the weakest base strength when deprotonated.Conjugate Acid-Base partners have a special relationship. Based on the Equilibrium Constant data can you determine and state that relationship? - Strong acids ionize into the weakest conjugate bases and vice versa.Auto-ionization of water:- Kw = [H3O+][OH-] = 1.0 x 10^-14- Pure water always has some hydronium and hydroxide present- Equal amounts means neutral- If there is more hydronium, it is acidic- If there is more hydroxide, it is basic- Addition of H3O+ causes reaction to shift left (OH- decreases)- Determine the [H3O+] & [OH-] at 25oC in 6.0 X 10-2 M HI(aq)- HI + H2O H3O+ + I-o [H3O+] = 6.0 x 10 ^-2 M (strong acid)o [OH-] = ?o Kw = [H3O+][OH-] = 1.0 x 10^-14o [OH-] = 1.7 x 10^-13 (plug in and solve)- CH3COOH(aq) + H2O(l)CH3COO- (aq) + H3O+ (aq) o Ka = 1.8 X 10-5o CH3COO-(aq) + H2O(l)CH3COOH (aq) + OH- (aq) Kb = ?pH and pOH:- pH = -log[H3o+]- Calculate the pH of 6X10-5 M HClO4o [H3O+] 6.0 x 10^-5o pH = 4.2- Calculate the pH of .077 M NaOHo pOH = -log [OH-]o pOH = 1.1- Kw = [H3O+][OH-]- Calculate pOH and [OH-] in a solution with a
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