CHM 104 1st Edition Exam 2 Study Guide Lectures 10 17 Lecture 10 February 18 How does Q relate to K What is the value of Q aA bB cC dD If Q K then the reaction is at equilibrium If Q K then the reaction system has too much product present the reaction proceeds to use those products to make more reactants If Q K then the reaction system has too much reactant present the reaction proceeds to use those reactants to make more products Lecture 11 February 20 What are Heterogeneous Equilibrium Calculations What is Le Chateliers Principle H2 g S s H2S g Sulfur is NOT involved in determining the EQ pressures of H2 and H2S BUT some of it will get USED H2 g I 0 200 C x E 0 200 x S s H2S g Kp 1 0 0 100 Q K Used x 0 100 x If an influence disrupts an equilibrium the reaction will respond by moving in a way that partially counteracts the disturbance and restores Equilibrium Disturbance Response Add Product Use Product EQ Shifts Remove Product Generate Product Suddenly increase Pressure decrease volume Response system will try to lower pressure Pressure is proportional to moles of gas Lecture 12 February 23 What are acids and bases What is the Arrhenius Definition What is the Br nsted Lowry Definition Acids Taste sour citric acid vinegar Can dissolve metals Neutralized by bases Bases Tastes bitter components of dark chocolate coffee feels slippery and reacts with skin oil to create soap like chemicals Arrhenius Definition Acid substance that produces H ions in aqueous solutions Base substance that produces OH ions in aqueous solution HCl is an acid HCl aq H aq Cl aq H is a very reactive species H aq H2O l NaOH is a base H3O aq NaOH aq Na aq OH aq Acids and Bases react to form H2O H OH H2O Br nsted Lowry Definition Acid substance that DONATES H Base substance that ACCEPTS H Acetic Acid Donates H to H2O HC2H3O2 aq H2O l H3O aq C2H3O2 aq NH3 Accepts H so it is a base NH3 aq H2O l NH 4 aq OH aq Notice in these examples that H2O can either accept H act as base OR donate H act as acid Amphoteric Lecture 13 February 25 What is Acid Strength and the Ionization Constant Strong Acids Completely ionizes in reaction with H2O HCl aq HCl l H3O aq Cl aq Ionized forms Other Strong Acids H2SO4 1st proton only HBr HNO3 HI HClO4 perchloric Weak Acids Weak acids only partially ionize in reaction with H2O Best thought of as an equilibrium HA aq H2O l H3O aq A aq The behavior ranges from ionizing very very little to almost 100 Common Weak Acids HF Hydrofluoric acid HC2H3O2 Acetic acid HCHO2 Formic acid Polyprotics H2SO3 Sulfurous acid H2CO3 Carbonic acid H3PO4 Phosphoric acid Strong H2SO4 aq H2O l HSO4 aq H3O aq Weak HSO4 aq H2O l SO42 aq H3O aq Don t Confuse Strength and Concentration Strength fraction of acid that ionizes to generate H3O fraction of base that ionizes to generate OH Concentration Amount of substance amount of acid or amount of base Strength of Acid and its Conjugate Base HCl aq H2O l H3O aq Strong Acid Cl aq Very Weak Base Strength Quantified by Acid Ionization Constant Ka HA aq H2O l H3O aq A aq Typical Ka s for weak acids range from 10 2 to 10 10 Lecture 14 February 27 What is the difference between a strong and weak acid What does X is small mean How do you calculate pH What is percent ionization Strong Acid pH of 0 10M HCl Unless the HCl is 10 6 M we don t worry about ionization of H 2O Weak Acid pH of 0 10 M HC2H3O2 Solution Both K s are small but Ka for acetic acid is a billion times bigger than Kw So ASSUME most all H3O comes from H2C2H3O2 X is small when Ka 10 4 Calculating Ka by measuring pH of solution The pH of 0 100 M HA solution is 5 00 what is the Ka H3O eq 10 pH 1 0 X 10 5M HA H2O A H3O I 0 100 0 0 C X X X E 0 100 1 0 X 10 5 1 0 X 10 5 1 0 X 10 5 Calculating concentration from pH measurement The pH of an acid with Ka 1 0 x 10 8 is 5 00 what is its concentration HA H2O l A H3O I a 0 0 C 1 0 X 10 5 1 0 X 10 5 1 0 X 10 5 E 1 0 X 10 5 1 0 X 10 5 1 0 X 10 5 H3O eq 1 0 X 10 5 Calculating ionization for an acid Important Trends H3O EQ as Ka increases H3O EQ as acid concentration increases ionization as Ka Mixtures of Acids Strategy Focus on the STRONGEST acid in the mix Lecture 15 March 2 How do you use solutions that contain bases How do you calculate pH What is the base ionization constant How do you classify compounds Solutions containing Bases Calculating pH The Strong Bases are all Strong Electrolytes Group 1A Group 2A LiOH Ca OH 2 NaOH Ba OH 2 KOH Sr OH 2 metal hydroxides Base Ionization Constant The smaller Kb is the weaker the Base is Classifying compounds as acids bases or neutral Group I and Group II are neutral species Li Ca2 K Mg2 Na Ba2 Conjugates of Strong Bases They have no effect on pH Ka x Kb constant If Ka for an acid is big then Kb for the conjugate base is small strong weak acid weak weak base There is an inverse relationship between the strength of a weak acid and the strength of its conjugate base Increasing Strength HCl strong Cl Negligible HF Ka 3 5 x 10 4 F Kb 2 9 x 10 11 HC2H3O2 Ka 1 8 x 10 5 C2H3O2 Kb 5 5 x 10 10 H C2H8N2 Ka 1 2 x 10 10 C2H8N2 Kb 8 3 x 10 5 Na OH Negligible strong Increasing Strength Cations conjugates of Strong Bases Na K Li Ca2 Ba2 Sr2 Anions conjugates of Strong Acids Cl Br I NO3 ClO4Lecture 16 March 4 I Mixture of two or more acids II Acid Strength III Molecular Structure How do you respond to a mixture of two or more acids Why is acid strength important Why is molecular structure important Polyprotic Acid Some acids have 2 or more ionizable protons Ka1 1 6 X 10 2 H2SO3 H2O HSO3 H3O Ka2 6 4 X 10 8 HSO3 H2O SO32 H3O H2A H2O HA H3O Ka1 HA H2O A2 H3O Ka2 Calculate the pH of a 0 100 M oxalic acid H2C2O4 solution Ka1 6 0 X 10 2 Ka2 6 1 X 10 5 H2C2O4 I C E 0 100 M X 0 100 X H2O HC2O4 H3O I 0 0 I X X I X X 6 0 X 10 2 X2 0 …