Popular in General Chemistry I
Popular in Chemistry
This 4 page Study Guide was uploaded by Olivia SaoBento on Monday November 16, 2015. The Study Guide belongs to CHEM 1111 at George Washington University taught by Besson, C in Fall 2015. Since its upload, it has received 45 views. For similar materials see General Chemistry I in Chemistry at George Washington University.
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Date Created: 11/16/15
Exam 3 Chemical Reactions aAbBcC 9 dDeEfF a b c d e f are stoichiometric coefficients A B C are reactants D E F are products States of matter H20S H20 H20g Determined by Temp and Pressure Balancing equations Rules 1 Conservation of mass9 atoms on left must be on the right same 2 Conservation of charge 9 charge on both sides must be the same Steps 1 List reactants and products 2 Isolate bocks that are the same on both sides 3 Balance a Rare elements 1st appear only once b Finish with other elements leave 0 for last c Continue systematically 4 Normalize9 make coefficients the smallest possible 5 Double check Types of reactions Dissociation aA9 bB cC Combination aA bB 9 cC Combustion aA bOz9 C02 H20 Limiting Reactants and yield Stoichiometry 9 ratio of moles of compounds to determine mass moles etc GSiOZ 10C 2Ca3PO429 10CO 6CaSi03 P4 6 moles of SiOz react with 10 moles of C Limiting reactants Excess9 wont react because of missing counterparts Limiting9 missing stops when it is all used up Steps to determining limiting reactants 1 Balance equation 2 Set ratio of mole in equation to moles that are given a If it is mass that is given convert to moles 3 If moles ofA is less than the calculated need of B then A is the Limiting in respect to B 4 Repeat if multiple reagents are present Yield Maximum theoretical yield9 the amount of moles of a product if all of the limiting reagent reacts to give products yield real amountmax theoretical 100 Dissolution Electrolytes 9 compound that dissolves in water to give a conducing solution Not e but ions that move So any compound that dissolves in water to give ons Examples 0 onic Compounds 0 Ionizable molecules Nonelectrolytes 9 compound that dissolve but don t give ions and don t conduct Strong acids and bases9 strong electrolytes Precipitation 9 formation of solid from mixture of liquidssolutions in a reaction Saturated Solution maximum concentration of a species Solubility Concentration of the solutions molL gL onic equations all aqueous species written as ions rather than compounds Net onic equations only ions that form a gas or solid and such compound are included AcidBase reactions Lewis Acid base Acids want to accept e pairs Bases want to donate e pairs Bronsted AcidBase Acids are proton donor Bases are proton acceptors Acidity is measured in pH potential Hydrogen pH log H30 Redox reactions Oxe9 Red Red90xe Reducing reagent e donor Oxidizing reagent e acceptor Being oxidized is reacting with oxidant and losing an e Redox couple OxRed Zn2Zn Rules of assigning oxidation 1 Sum of Ox is net charge 2 F and halogens 9 3 Li Na K 9 Be Mg 9 II B Al 9 4 H 9 unless other rules win 5 0 9 unless other rules win Balancing Redox Reactions 1 Identify redox coupes 9 0x numbers change Fe203Fe C02CO 2 Write 12 equations a Write redox couple on each side Fe203 9 2Fe b Balance 0 with H20 Fe203 9 2Fe 3 H20 c Balance H with H Fe203 6H9 2Fe 3 H20 d Balance charge with e Fe203 6H 6e9 2Fe 3 H20 C0 H20 9 C02 2H 2e 3 Eliminate e Fe203 6H 6e9 2Fe 3 H20 3x C0 H20 9 C02 2H 2e FeZO3 3C0 9 3C02 2Fe 4 Simplify and normalize Thermochemistry study of energy transformations Energy Chemical E in molecules because of structure of atoms Thermal random movement of particles Internal total energy of system U Joule J kngs2 Work W kngs2 Energy Exchange Work 9 exchange tofrom mechanical energy Heat 0 9 exchange of thermal energy 1St law of thermodynamics 9 internal energy U of a closed system AU W Q always define the system only applies to closed Enthalpy 9 H U PV PressureVolume Work 9 W P AT Constant volume 9 AUQV Constant Pressure 9 AH Qp Enthalpies of transformation In any given reaction ArH ZAH products ZAH reactants Calorimetry Specific Heat 5 amount of heat needed to raise 1 g of a substance 1 C 9 JgC Heat Capacity c amount of heat to raise and object 1 C JC qmsAT qcAT Where m mass and ATTinitiaI Tfinal qVdsAT where mdV AH m mol C qhotqcold ca39 ATcold Hess s Law enthalpy is a state function so path does not matter AHA93AHA9CAHC93 AHA9DAHD9EAHE93 Reactions can be manipulated to cancel out compounds to reach desired reaction only if Enthalpies are also manipulated Bond Dissociation Enthalpies The energy needed to break a bond between two atoms AFH BDE reactants BDE products
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