CHEM 2211 1nd Edition Exam 1 Study Guide Lectures 1 8 Lecture 1 August 20th Remembering general chemistry Important questions 1 What are the main rules and principles a Are any of them related 2 What are the basic types of bonding 3 How are they different 4 What are the types of structures from this lecture 5 Show examples of each and how they are different 1 What are the main rules and principles There are 3 principles and 1 rule Quantum number principle Aafbau s principle Pauli principle Hunds rule 2 of the principles and hunds rule relate to electrons and how to assign them to atomic orbitals Aafbau s principle tells us the first step to assigning electrons to orbitals That an electron always goes into the lowest energy orbital available Note the closer the orbital to the nucleus the lower the energy o S P D F o Also 1S 2S 2P 3S 3P 3d etc Pauli exclusion principle gives us the second piece to placing electrons No more than two electrons can occupy each atomic orbital Also the electrons must have opposite spins Hunds rule last rule to assigning electrons to orbitals When there are two or more atomic orbitals with the same energy and electron will occupy an empty orbital before it will pair up with another electron This can all be represented by doing an electron configuration of an atom Sodium atomic number 11 Orbitals 1s 2s 2p 2p 2p 3s Hunds rule is representing the 2p part of this electron configuration First 1s 2s 2p 2p 2p the electrons occupy each 2p orbital in the same spin direction first Then 1s 2s 2p 2p 2p 3s What are the basic types of bonding polar results from a bond between two nonmetals of different electro negativities non polar results from a bond between two nonmetals but they are the same electro negativities ionic bond between a metal and nonmetal where one transfers an electron leaving a charge covalent bond that involves the sharing of electrons between atoms could be polar or nonpolar types of structures There are 3 from this lecture 1 lewis dot lines are drawn between atoms to show bonds dots are put around atoms to show lone electrons 2 Kekule same basic structure as lewis lone electron dots are omitted 3 Condensed no lines to show connections just atomic symbols put in order Lewis dot structure H C C H Kekule structure H C C H Condensed structure CHCH Lecture 2 August 22nd Important questions 1 How do polar bonds relate to polar molecules 2 What are the parts of a perspective diagram 3 How to draw skeletal structures a Why we use them in organic chemistry How do polar bonds relate to polar molecules A polar molecule has to have polar bonds within it but not every molecule with polar bonds is a polar molecule A polar molecule has to have polar bonds and be non symmetrical in other words the bonds on either side of the center molecule cant cancel out A non polar molecule is perfectly symmetrical so the bonds on either side of the center molecule cancel out each other They have the same electronegativity difference Parts of a perspective diagrams Wedges Dashed wedges Lines These parts show which plane each atom is in off a center molecule Wedges show atoms coming in front of the center molecule plane Dashed wedges show atoms going behind the center moles plane Lines show atoms in the same plane as the center molecule How to draw skeletal structures and why we use them Skeletal structures are the most condensed and simple structures which is why we use them in organic chemistry Skeletal structures are just line structures they omit drawing hydrogens and carbons Carbons are represented by the points of each line and hydrogens are implied Anything that s not a C or H gets drawn in in its place This skeletal structure Is hexane Lecture 3 august 25th Important questions 1 2 3 4 5 What is an acid What is a base What is a strong acid What is a strong base What is pKa a How to use pKa to determine equilibrium 6 What is pH What is an acid An acid is by basic definition a proton donator What is a base A base is a proton acceptor What is a strong acid There is a list of strong acids HCl HBr HI HClO3 HClO4 H2SO4 Anything that is not a strong acid is a weak acid What is a strong base Strong bases are found in the first two groups on the periodic table NaOH Ca OH 2 KOH Etc Anything that is not a strong base is a weak base Weak bases conjugate acids are very strong acids Strong bases conjugate acids are weak acids And vis versa for acids conjugate bases What is pKa pKa is the acidity of a given hydrogen atom lower the pKa the more acidic the atom pKa is determined by the equation log Ka pKa Ka is the acid dissociation constant If Ka is less than 1 than reactant are predominate at equilibrium If Ka is greater than 1 than products are predominate at equilibrium What is pH Measure of acidity it is measured on a scale from 0 14 Strong acids are on the lower part of the scale usually between 0 3 Weak acids between 4 6 Neutral is 7 Weak bases are 8 11ish Strong bases are on the higher part of the scale 12 14 Lecture 4 5 august 27th 29th Important questions 1 In order of increasing acidity what are the main groups of this lecture 2 How do you predict acid base reactions 3 What factors affect the pKa Main groups of this lecture There are four main groups addressed in this lecture Carboxylic acids Alcohols Protonated alcohols Amines In order of increasing acidity they go Amines Alcohols Carboxylic acids Protonated alcohols Remember you predict the acidity of a give molecule based on its pKa Greater the pKa less acidity the compound Lower the pKa stronger the acid more acidic the compound Amines pKa 40 Alcohols pKa 16ish Carboxylic acids pKa 3 5 Protonated alcohols pKa 1 Acid base reactions pKa is also used to predict an acid base reaction By looking at the pKa of each reactant in the reaction we can tell which one will be the acid and which one will be the base The reactant with the lower pKa will act as the acid an thus the reactant with the high pKa will be the base From this the reaction can be preformed knowing which reactant will donate and which will accept Factors affecting pKa There are 5 factors that affect pKa 1 2 3 4 Electronegativity Hybridization Size Inductive substitutes 5 Resonance They each affect pKa in a different way Electronegativity The greater the difference between two atoms electronegatities the more the bond The more polar the bond the more acidic the pKa Hybridization Sp sp2 sp3 Triple bond is more acidic then double Double bond more acidic than single