CHEM 2211 1st Edition Lecture 4 Outline of Last Lecture I. Chapter 1: over view of structure and bonding Outline of Current Lecture II. Practice questions a. Answers and explanations III. Chapter two: Acids and Bases a. Defining types of Acids and Bases b. 3 definitions IV. Strengths of Acids and Bases V. pKa and pH a. Definitions and equations Current lecture notes II. Practice questions 1. What is the hybridization of a double bonded O atoms i. Example C-CH2=O b. SPc. SP2d. SP3i. Answer and explanation will be in order after last question 2. Of the gas phase halogen compounds, formula HX, which has the weakest bond a. HFb. HClc. HBrd. HIQuestion #1 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.- Answer is C - Why? Count the number of electron domains occupied two lone pair domains and one double bond domain o 3 total domains = SP2 hybridization Question #2 - Answer is D - Why? o The weakest bond will be made by the longest bond length o Bond length increases as atomic radius increases o Iodine is the largest atom in the group causing it to have the longest bond length III. Chapter two: Acids and Bases Types of acids and bases Arrhenius- Acid: a hydronium ion donor - Base : a hydroxide ion donor Bronsted- Lowrey - Acid: hydronium ion donor - Base: lone pair donor o :NH3Lewis - Acid: lone pair donor - Base: lone pair acceptor Example of Lewis Acid and base BH3 + :NH3 BH3NH3 - This reaction is a lewis acid adduct IV. Strengths of Acids and Bases Acids and bases can be either strong or weak Strong acids:- HCl- HBr- HI- HClO3- HClO4- H2SO4Strong Bases: - Strong bases can be found in groups 1 and 2 on the periodic table - A1 and A2 hydroxides - Ex: NaOH and Ca(OH)2, KOH Weak acids and bases - Weak acids o Anything else (besides the strong acids atoms) combined with H+ - Weak baseso Anything else (besides the strong base atoms)Water can be either an acid of base depending on what it is acting with General equations for acids and bases- What you used in general chemistry looked like this: o HA (aq) + H2O(l) A-(aq) + H3O +(aq) - Strong acid and base o HA + :B A- + BH+ - Base o :B + H2O HB + OH- Note: single arrow shows reaction goes to completion. Double headed arrow shows equilibrium can be reached between reactants and products. V. pKa and pH pH - measure of acidity on a scale from 0-14 - scale can go as high as 16 - between 0 and 7 is acidic - 7 is neutral (water)- Between 7 and 14 is basic - Ex: table to the right Equation for pH - pH = -log [H+]- [H+] = molarity - Molarity = moles/ liters (mol/L) pKa - Acidity of a given hydrogen atom - Lower the pKa the more acidic it is Equation for pKa- pKa = -log Ka Ka - Ka is the acid dissociation constant - It is determined by ( aqueous products/ aqueous reactants) o Ex: HA + H2O H3O+ + A- o a b c d- Reactant a is aq - Products c and d are aq So: [H3O+] [A-] / [HA] = Ka Ka also determines which side is predominate in a double headed arrow reaction like this one - If Ka is less than (<) 1 o Reactants are predominate - If Ka is greater than (>) 1 o Products are
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