CHM2046 Final - Chapters 11-20 PDF

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Chapters 11-20...

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Chapters 11 - 20 Concepts Chapter 11 IMF present in all molecules (intermolecular forces) ● All contain dispersion ● Polar molecules = dipole - dipole ● Hydrogen bonding w/ N,F, O ● Ion dipole occurs w/ water & ionic compound Surface Tension ● Molecules at surface experience less contact with other molecules and are thus tightly held to each other (minimize S.A.) Vaporization & Vapor Pressure ● Vaporization is characterized by having enough thermal energy to overcome IMF ● Molecules at surface are able to break free easier ● Molecule with low IMF is more volatile ● Can calculate energy required to vaporize by : Hvap x mols Vapor Pressure ● As gas increases, condensation rate increases ● Temperature rise = increase energy for particles to evaporate ● Boiling point = temp at which vapor pressure = ext press (at lower pressure, water boils at lower point and vise versa) Clausius Clapeyron Equation ● Relationship between temperature and vapor pressure ● Normal boiling point occurs at 1 atm ● Critical point: cannot tell difference between liquid and gas Sublimation: solid to gas (endo) Deposition: gas to solid (exo) Fusion: solid to liquid (endo) Vaporization: liquid to gas (endo) Condensation: gas to liquid (exo) Chapter 12 - No Questions Chapter 13 ● ● ●

Homogenous: appears to be one substance Solute: the component that changes state Solvent: keeps its state

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Entropy is a measure of energy dispersal (mixes because allows for spread out of energy across a volume) IMF on solutions: like dissolves like. So look for more similar IMF Saturated solution: in dynamic equilibrium, no dissolution , saturation [ ] depends on temp and pressure of gases Supersaturated: more solute than saturation Henry’s Law: solubility of a gas is directly proportional to its partial pressure Sgas=KhPgas Concentrations ○ Molarity = mol solute/ L sol’n ○ Molality = moles solute / Kg solvent ○ Mass percent = grams solute / 100 grams solution ○ Mol fraction = moles solute / total moles in solution ○ Mole percentage = fraction x 100

Finish this chapter! Chapter 14 Rate = amount concentration changes in an amount of time ● [Product] / time = - [reactant] /  time Instantaneous rate: change in concentration at particular time ● Slope of a line, tangent to curve Catalysts: increase speed of reaction without being used up ● Increase temperature , increases concentration generally speeds up the reaction Rate Law ● Rate = k[A]n[B]m ○ n & m = order ○ [ ] = concentration ○ k = rate content ● Experimentally determined ○ 0 : concentration has no effect on rate ○ 1 : concentration directly proportional to rate (2 x [ ] = 2 x rate ) ○ 2 : concentration is exponentially related to rate (2 x [ ] = 4 x rate) Integrated Rate Law ● Used for finding concentration at a given time (y = mx + b) ● 0 : [A] = -k + [A] ● 1 : ln[A] = -k + ln[A] ● 2: 1/[A] = k + 1/[A]

Half-life = time for concentration to decrease to half the original ● 0 : t ½ = [A]/2k ● 1 : t ½ = .693 / k ● 2 : t ½ = 1/k[A] The Effect of Temp on Rate Reaction Mechanism ● Elementary steps of a reaction, will sum to total reaction ● Overall does not contain catalyst or intermediate ○ Catalyst : appears as ‘reactant’ and in products ○ Intermediate : shows as product and is then immediately used up ● Rate determining step : slowest step

Chapter 15 ● ●

Can have forward and backwards reaction Dynamic equilibrium : rate of forward = rate of reverse ○ K = [C][D] / [A][B] ○ K > 1 favor products at equilibrium* ○ K < 1 favor reactants at equilibrium* ○ Pure solids and pure liquids are not considered in equilibrium

The Reaction Quotient ● Helps to determine in which direction reaction proceeds, looks at concentration at any time ● Calculate same way as k ● Q < K proceed to right ● Q > K proceed to left ● Q = K reaction is at equilibrium Le Chatelier's Principle ● If we disturb the equilibrium, the reaction will adjust itself to return to equilibrium ● A+B⇆C+D ● Add reactant - shift right ● Add product - shift left ● Remove reactant - shift left ● Remove product - shift right ● Changing the volume of the container will shift the reaction : ○ Increase volume - to side with more gas particles ○ Decrease volume - to side with less gas particles ● Adding or removing heat ○ If endothermic, treat heat as a reactant

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If exothermic, treat heat as product

Chapter 16 Arrhenius Theory ● Acids dissolve to form H+, bases dissolve to form OHBronsted - Lowry Acid- Base ● Acid donates H+, Base accepts H+ Amphoteric Substance: can act as acid or base (ex. water) Conjugate Pairs: Conjugate acid/base pairs differ by 1 hydrogen (H2O & OH-) Strong Electrolytes: completely ionizes in water (strong base or acid) Strong Acids: H2SO4, HClO4, HNO3, HBr, HI, HCl Strong Bases: Group 1 & 2 , also OH ● ●

As strength of acid increases, the strength of conjugate base decreases (vice versa) The farther to the right the equilibrium lies, the stronger the acid or base, makes sense because will ionize

Acid Ionization Constant: Ka = [Acid-] [H3O+] / [HAcid] Ion product of water: Kw = [OH-] [H3O+] = 1.0 x 10-14 pH = -log[H3O] pOH = -log[OH] [Kb][Ka] = 1.0 x 10-14 pH + pOH = 14 ; pKa + pKb = 14 ● ●

The stronger the acid, the smaller the pKa The stronger the base, the smaller the pKb

Polyprotic Acids : multiple H’s , consider only first ionization ● The conjugate base of a strong acid is neutral ● The conjugate acid of a strong base is neutral ● The conjugate base of a weak acid is a weak base ● The conjugate acid of a weak base is a weak acid Periodic Trends ● Acidity : increase electroneg , decrease in bond strength Oxyacids: number of oxygens increase , acidity increases

Lewis Base: electron pair donor, usually an anion Lewis Acid: electron pair acceptor , usually empty orbital, usually small, highly charged cations

Chapter 17 Buffer ● Resists change in pH ; composed of acid and its conjugate base ● Use henderson hasselbalch for this and when a weak acid or weak base is titrated ○ pH = pKa + log [base]/[acid] ● Buffers are more effective at larger and more equal concentration ● Is asked what buffer is most effective at achieving a specific pH look at closest pKa Titration ● Adding a base to an acid (or vise versa) until an equivalence is reached (equivalence = number moles is the same) ● For strong acid/base = equivalence is at pH 7 ● For weak acid with strong base = equivalence is at pKa ● For weak base with strong acid = equivalence is at pKb Solubility Equilibria ● All ionic compounds dissolve to some degree ● Molar solubility: amount that will dissolve Common ion effect* ● Addition of a soluble salt that contains one of the ions of the ‘insoluble’ salt decreases solution of the ‘insoluble’ salt Precipitation ● Occurs when the concentration of the ions exceed the solubility ● Q > Ksp = precipitate will form ● Q = Ksp = solution is saturated so no precipitation ● Q < Ksp = solution is unsaturated so no precipitation

Chapter 18 Spontaneous reaction ● occurs without outside intervention ● Also tells direction in which and extent reaction goes

Entropy ● Highest energy dispersal (increase with state Gas > Liquid > Solid) Gibb’s Free Energy ● G =T H - T S ● -△ G = spontaneous ● + G = nonspontaneous ● If exothermic / positive entropy = spontaneous all the time

Chapter 19 ● ● ● ● ● ● ● ● ● ● ●

Oxidation: loss of electron, becomes more positive Reduction: gain of electron, becomes more negative Voltaic cell: produces electrical current from a spontaneous reaction Electrical current: measured in amperes Potential energy: difference in volts Oxidation occurs at anode = losing electrons Reduction occurs at cathode = gain electrons Electrons: flow from electrode with more negative charge to more positive charge Half-life reaction with more + electrode attracts electrons so reduction Half-life reaction with more - electrode repels electrons so oxidation E = potential difference / charge

Chapter 20 Alpha decay: loss of alpha particle Beta decay: neutron break to proton and electron Positron Emission: anti-particle of an electron (one less proton) Electron Capture: proton + electron = neutron

What is the definition of Half-Life? The amount of time it takes for a concentration to fall to half its original value. Reduction Potential Reducts Reaction Erosion Calculate Voltage...