Chem I Chapter 9 Review + Chapter 5 PDF

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Lecture notes on bonding and thermochemistry with problems and equations from Dr. Ariyadasa's course...

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Sigma bonds: ● Head to head overlap ● Cylindrical symmetry of electron density about the internuclear axis ● Stronger than pi bonds Pi bonds: ● Sideways overlap ● Electron density above and below the internuclear axis Double bond: ● 1 pi bond and 1 sigma bond Triple bond: ● 1 sigma bond and 2 pi bonds Example problem: There are ________ sigma bonds and ________ pi bonds in CH2CHCH3 Answer: 8,1 Localized or delocalized electrons: ● Bonding electrons (sigma or pi) that are specifically shared between two atoms are called localized electrons ● In many molecules, we cant describe all electrons that way (resonance). These are called delocalized electrons Resonance structures: ● No single, double, or triple bonds; just an average of the bonds Thermochemistry: ● Study of energies given off by or absorbed by reactions ● Energy - The ability to do work or transfer heat ○ Potential energy - stored energy ○ Kinetic energy - the energy of motion The first law of thermodynamics: ● Energy can be converted from one form to another, but it cannot be created or destroyed Types of systems: ● Open- can exchange heat, energy, and mass with its surroundings ● Closed- can only exchange heat with its surroundings, not mass ● Isolated- cannot exchange heat or mass with its surroundings Internal energy: ● The sum of all kinetic and potential energies of all components of the system ● E is not generally known, only how it changes (delta E) ● The change in internal energy is the final energy of the system minus the initial energy of the system ● If delta E is greater than 0, then the system absorbed energy ● If delta E is less than 0, then the system released energy Thermodynamic quantities have 3 parts: 1. A number 2. A unit

3. A sign a. A positive delta E results when the system gains energy from the surroundings b. A negative delta E results when the system loses energy to the surroundings...