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UB CHE 102 - Exam 1 Study Guide

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Chem 102 1st EditionExam # 1 Study Guide Chapter 13:A. Units of concentration:Mass%= (Mass of component/ total mass of solution) x100Mole fraction (X)= moles of solute/ total moles of solventMolarity (M)= moles of solute/ liters of solutionMolality (m)= moles of solute/ Kg solvent Moles (mol)= mass(g)/ MMB. Energies of Solution1. Separation of solute molecules- endothermic solute= small amount2. Separation of solvent molecules- endothermic solvent= large amount3. Formation of solute-solvent interaction- exothermicEnthalpy Formula- ΔH= ΔH1 + ΔH2 + ΔH3C. Energy Changes & Solution ProcessHeat= specific heat x mass (solute and solvent) x ΔTRULE= Like dissolves like… such as, non-polar dissolves non-polar. Water is non-polar therefore it will be dissolved by the most non-polar substance. D. Hydrophilic vs. hydrophobic-Hydrophilic- “likes water” Has to have presence of ions, dipole moment and LDF. E. Boiling-Point Elevation ΔTb=i  m  Kb K=constant m=molality i= van’t Hoff factorThe higher the ΔTb the higher the boiling point.F. Freezing Point DepressionΔTf= i x m x Kf K= constant m=molalityThe higher the ΔTf the lower the freezing point. G. Osmosis and Osmotic Pressure/ Vapor pressureπ= MRT π= Osmotic pressure M=Molarity R=constant, .08206 T=Temp (K)π is measured in atm. Raoult’s Law- Vapor pressure equation Pa= Xa Pa° Pa- vapor pressure with solute Pa°-vapor pressure without solvent Xa- Mole fraction of A in solution H. Colligative Properties of ElectrolytesSome ions do not dissolve to their full extent. Van’t Hoff factor, i= moles particles in solution/ moles solute dissolvedi= 1 for non-electrolyteChapter 14:A. Intro. To Reaction RatesAverage Rate= -ΔH[x[/ Δt= Δ[y]/Δt x= reactants (disappearance) y=products(appearance)Rate=k(reactant 1) ^m (reactant 2) ^n m and n refer to order k= rate constantZero order- Change in concentration of reactant produces no effectFirst order- Doubling concentration cause rate to doubleSecond order- Doubling concentration results in a 2^2 increase in rateFirst- Order Reactants: Ln [A]t= -kt + ln [A]0Half-Life: t1/2= -(ln1/2)/k= .693/kSecond- Order Reactants: 1/ [A]t =kt+ 1/[A]0Temp increase, rate of reaction increasesB. The Collision ModelIn order for molecules to react they must collide. The greater the number of collisions the fasterthe rate. The more molecules present, the greater the probability of collisions. The higher the temp, the more energy available to the molecules, therefore the faster the rate. C. Activation EnergyMolecules must present a minimum amount of energy to react, in order to break bonds. Activation Energy is the minimum energy required to initiate a chemical reaction. Arrhenius Equation: k=Ae ^(-Ea/RT)D. CatalystsOperate by increasing the number if effective collisions, increasing reaction rate. Intermediates may be added to these reactions. These are molecules that get cancelled out of the first equations and do not show up in the final equation. Chapter 15:A. Chemical EquilibriumThe point at which the concentrations of all species are constant. The opposing rates are equal, forward and reverse reaction. These reactions are represented by a double arrow. Equilibrium constant expression:      baqpcKBAQP Kc is the equilibrium constant. The Kp is the equilibrium constant for reactions involving gases:     baqpPPPPPKBAQPKp is based on partial pressure measured in atm. Kp = (RT) Dn Kc Δn- product coefficients- reactant coefficients of GASES ONLYThe equilibrium constant, K, is the ratio of products to reactants. The larger the K the more Products are present at equilibrium, the smaller the K more reactants present at equilibrium. Q is defined as the reaction quotient: Q=K only at equilibriumaA + bB(g) pP + qQ       baqpQBAQPIf Q>K the reverse reaction must occur to reach equilibrium.If Q<K the forward reaction must occur to reach equilibrium. B. Le Chatelier’s PrinciplePressure increases, products increase. And as volume decreases, pressure increases. However, ifyou increase pressure by adding a gas there is no effect on equilibrium. High pressures favor phase which occupy lower volume. Temp. decreases, products increase. Endothermic reactions favor the forward reaction while exothermic favor the reverse. Adding a reactant or product shifts the equilibrium away from the increase. If you are having trouble, go over mastering chem, use the hints and study them. Do practice tests, and study the concept of the questions you are getting


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