# Shared Flashcard Set

## Details

Chemistry Test 3
N/A
79
Chemistry
04/25/2010

Term
 Solving Equilibrium Problems
Definition
 Balance the equation Write the equilibrium expression List the initial concentratsions Calculate Q and determine the shift to equilibrium Define equilibrium concentrations Substitute equilibrium concentrations into equilibrium expression and solve Check calculated concentrations by calculating K
Term
Definition
 5% test: if a simplification like this changes the area of simplification by less than 5% then the simplification is valid. If the change is 5% or greater use the quadratic equation.
Term
 Le Chatelier's Principle
Definition
 when a system at equilibrium is subjected to a change in temperature, pressure or concentration of a reacting species, the system responds by attaining a new equilibrium that offsets the impact of the change.
Term
 Effects of Changes on the System
Definition
 Concentration: the system will shift away from the added component.   Temperature: K will change depending upon the temperature (treat the enery change as a reactant).   Pressure: a) adding of inert gas does ont affect the equilibrium position. b) decreasing the volume shifts the equilibrium toward the side with fewer moles.
Term
 Arrhenius acid   Arrhenius base   Bronsted-Lowry acid   Bronsted-Lowry base
Definition
 produces H+ in aqueous solutions.   produces OH- in aqueous solutions.   H+ donor   H+ acceptor
Term
 Strong acid
Definition
 Ionization equilibrium lies far to the right (products). Yields a weak conugate base K = large Completely breaks apart in water
Term
 Weak acid
Definition
 Ionization equilibrium lies far to the left (reactants). Weaker the acid, the stronger its conjugate base. Does not break apart much.
Term
 Strong Acids
Definition
 HCl hydrocloric acid HBr hydrobromic acid HI HClO4 perchloric acid HNO3 nitric acid H2SO4 sulfuric acid
Term
 Strong Bases
Definition
 LiOH NaOH KOH RbOH CsOH Ca(OH)2 Sr(OH)2 Ba(OH)2
Term
 Self Ionization of Water
Definition
 has a reaction with itself   Amphoteric: can behave as either an acid or base   H2O + H2O --> H3O+ + OH-   Kw = 1.0 x 10-14
Term
 Acidic   Basic   Neutral
Definition
 H+ > OH-      pH < 7   OH- > H+     pH > 7   H+ = OH-       pH = 7
Term
 Acids
Definition
 Larger Ka value = stronger acid Smaller pKa value = stronger acid   will have H+ bound to F N or O atoms that can be donated
Term
 pH Scale
Definition
 pH = -log[H+]   pH decreases as H+ increases   The acid(base) dominates pH (pOH) if: its concentration is greater than 10-6M (pure water would donate 10-7M H+) its Ka(Kb) is larger than Kw
Term
 Percent Ionization aka Percent Dissociation
Definition
 [H3O+]/[HA] x100%   more concentrated   more diluted <---acid conc ----- ----percent dissociation--> <---[H+] conc-------
Term
 pKw = pH + pOH = 14
Definition
Term
 Kw
Definition
 Product of the ionization constants of an acid conjugate base pair is the ionization constant of water   Ka x Kb = Kw   pKa + pKb = pKw
Term
 Bases
Definition
 Larger Kb = Stronger base Smaller pKb = Stronger base   will have N or O atoms that have lone pair electrons that can attract H+
Term
 pOH
Definition
 pOH = -log [OH-]   pOH > 7 acidic pOH < 7 basic pOH = 7 neutral
Term
 Polyprotic Acid
Definition
 an acid that contatins more than one ionizable H atom per molecule   the first proton is the easiest to remove (largest Ka)   After that there is an anion that the proton would be removed from.   It gets progressively more difficult to removed succeeding protons
Term
 Acid-Base Properties of Salts
Definition
 cations may act as acids in water except: Li+, Na+, K+, Rb+, Cs+, Ca2+, Sr2+ (strong bases with hydroxide removed)   these are the conjugate acids of strong bases and are such super weak acids that they will not act as an acid in water   these are pH neutral
Term
 Acid-Base Properties of Salts
Definition
 Anions may act as bases in water Except: Cl-, Br-, I-, NO3-, HSO4-, ClO4-, BrO4-, IO4- (strong acids without H+)   these are the conjugate bases of strong acids and are such super weak bases that they will not act as a base in water   these are pH neutral
Term
 The Effect of Structure on Acid Base Properties
Definition
 Factors effecting acid strength: bond polarity (high is good) bond strength (low is good)
Term
 Oxyacids
Definition
 Contains the group H-O-X (x=everything else) for a given series the acid strength increases with an increase in the number of oxygen atoms attached to the central atom. The greater the ability of X to draw electrons toward itself, the greater the acidity of the molecule. the greater the electron density, the easier the proton will leave. The stronger the acid.
Term
 Molecules containing the grouping H-O-X can behave as acids
Definition
 the acid strength increases with increasing electron-withdrawing ability of X. This enables the H+ to be released. Ex. HClO4 If X has a very low electronegativity, the OH- can be lost and the solution will be basic Ex. NaOH
Term
 Lewis Acid   Lewis Base
Definition
 electron pair acceptor   electron pair donor
Term
 Common Ion Effect
Definition
 The suppression of the ionization of a weak electrolyte caused by the addition of an ion that is also a product of the ionization equilibrium of the weak electrolyte.   Shift in equilibrium position that occurs because of the addition of an ion already involved in the equilibrium reaction   an application of Le Chatelier's principle   the strong acid causes less of the weak acid to dissociate than would be expected
Term
 Buffered Solutions
Definition
 resist a change in pH   they are weak acids or bases containing a common ion   after addition of strong acid or base, deal with stoichiometry first, then the equilibrium
Term
 Buffer Solutions
Definition
 a solution with appreciable amounts of a weak acid and its conjugate base that resist change in pH upon addition of an acid or base
Term
 Henderson-Hasslebalch  Equation for BUFFERS
Definition
 pH = pKa = log nbase/nacid
Term
 Characteristics of Buffered Solutions
Definition
 buffers contian relatively large amounts of weak acid and corresponding conjugate base added H+ reacts to completion with the conjugate base Added OH- reacts to completion with the weak acid The pH in the buffered solution is deteremined by the ratio of the concentrations of the weak acid and weak base. As long as this ratio remains virtually constant. This will be the case as long as the concentrations of the buffering materials (HA and A- or B and BH+) are large compared with amounts of H+ or OH- added
Term
 Buffering Capacity
Definition
 the amount of acid or base that a buffer can neutralize before its pH changes appreciable   when the ratio nbase/nacid is close to 1, the buffer has its maximum buffer capacity.
Term
 Buffer Region
Definition
 a weak acid/conjugate base pair acts best as a buffer around the pH region equal to the pKa. Usually within 1 pH unit of the pKa
Term
 Titration Curve
Definition
 Plotting the pH of the solution being analyzed as a function of the amount of titrant added   equivalence (stoichiometric) point- point in the titration when enough titrant has been added to react exactly with the substance in solution being titrated
Term
 Acid Base Indicators
Definition
 a substance whose color depends on the pH of the solution to which it is added.   The indicator is a weak acid. It has a different color than its conjugate base.   The equivalence point is not necessarily the same as the end point (but they are ideally as close as possible)   the color change will become apparent when about 10% of the initial from of the indicator has been converted
Term
 Solubility
Definition
 how much of a substance that will dissolve in a given amount of solvent at a given temperature
Term
 Solubility Product
Definition
 the equilibrium constant expression for a salt dissolving in water
Term
 ksp values
Definition
 increase the number, more it breaks apart   decrease the number, less it breaks apart   lower ksp more solid that will dissolve
Term
 Precipitation
Definition
 mixing two solutions of ions   Q>Ksp : precipitation occurs and will continue until the concentrations are reduced to the point that they satisfy Ksp: too many products   Q< Ksp : no precipitation occurs: too many reactants, make more products
Term
 complex ion
Definition
 a charged species consistening of a metal ion surrounded by ligands
Term
 Ligands
Definition
 a lewis base (molecular ion having a lone electron pair that can be donated to an empty orbital on the metal ion to form a covalent bond)
Term
 Formation (stability) constant K
Definition
 Equilibrium constant for each step of the formation of a complex ion by the addition of an individual ligand to a metal ion or complex ion in aqueous solution
Term
 two strategies for dissolving a water-insoluble ionic solid
Definition
 if the anion of the solid is a good base, the solubility is greatly increased by acidifying the solution in cases where the anion is not sufficiently basic, the ionic solid often can be dissolved in a solution containing a ligand that forms stable complex ions with its cation.
Term
 Spontaneous Process
Definition
 a change that occurs in a system left to itself; once started no external action is necessary to make the process continue.   exothermic heat given off; combustion   one that occurs without outside intervention
Term
 nonspontaneous process
Definition
 will not occur unless some external action is continuously applied
Term
 Thermodynamics
Definition
 lets us predict whether a process will occur but gives no information about the amount of time required for the process
Term
 Entropy
Definition
 thermodynamic property related to the degree of disorder in a system   nature tends toward disorder.   increase if: liquisd are formed from solids gases are formed from either solids or liquids the number of molecules of gas increases as a result of a chemical reaction the temperature of a substance increases
Term
 Entropy change, deltaS
Definition
 the difference in entropy between two states
Term
 Positional Entropy
Definition
 a gas expands into a vacuum because the expanded state has the highest positional probability of states available to the system   S solid < S liquid << S gas   the change in positional entropy is dominated by the relative numbers of molecules of gaseous reactants and products
Term
 Second Law of Thermodynamics
Definition
 in any spontaneous proces there is always an increase in the entropy of the universe   the entropy of the universe is increases   delta Suniv> 0 where delta Suniv = delta Ssys + delta Ssurr   for a spontaneous process   the sign of delta Ssurr depends on the direction of the heat flow. The magnitude of delta Ssurr depends on the temperature
Term
 delta Ssurr = qrev/T = delta H/T   qrev = heat gained in a reversible process -Joules   T = temperature (kelvin)   the change to the system is the reverse of the change to the surroundings delta Ssurr = delta H/T = -delta H sys/T
Definition
Term
 Free Energy
Definition
 delta G = delta H - TdeltaS (from the standpoint of the system)   a process (at constant T, P) is spontaneous in the direction in which free energy decreases   a [-] delta G means [+] deltas Suniv
Term
 Gibbs Free Energy, G
Definition
 delta G negative spontaneous delga G positive nonspontaneous delta G zero equilibrium
Term
 Third Law of Thermodynamics
Definition
 the entropy of a perfect crystal at 0K is zero because S is explicitly known (=0) at 0K, S values at other temps can be calculated The more complex the molecule, the larger the entropy
Term
 Dependence of Free Energy on Pressure
Definition
 delta G = delta G zero + RT ln(Q)   R gas law constant 8.3145 J/k*mol T: temperature in Kelvin Q: reaction quotient (in partial pressures) Delta G zero: free energy change at the standard state   Q = K
Term
 Free Energy and Work
Definition
 maximum possible useful work obtainable from a process at constant temperature adn pressure is equal to the change in free energy.   Wmax = deltaG Achieving the maximum work available from a spontaneosu process can occur only via a hypothetical pathway. Any real pathway wastes energy. All real processes are irreversible First law: cant have more than start with Second law: b/c disorder (entropy)
Term
 Electrochemistry
Definition
 the study of the interchange of chemical and electrical energy
Term
 oxidation reduction (redox) reaction
Definition
 involves a transfer of electrons from the reducing agent to the oxidixing agent.
Term
 oxidation   reduction   reducing agent   oxidizing agent
Definition
 loss of electrons   gain of electrons   electron donor   electron acceptor
Term
 balancing by half-reaction method in Acid
Definition
 Write a separate reduction, oxidation reactions: For each half reaction: Balance elements except H, O balance O using H2O balance H using H+ Balance charge using electrons multiply by interger to equalize electron count add half reactions check that elements and charges are balanaced
Term
 Half reaction Method- balancing in base
Definition
 balance as in acid Add OH- that equals H+ ions (both sides) Form water by cominbing H+, OH- Check elements and charges for balance
Term
 Galvanic Cells
Definition
 a device in which chemical energy is changed into electrical energy   this is done with a oxidation-reduction (redox) reaction
Term
 Salt bridge
Definition
 a U-tube filled with an electrolyte that connects the two compartments of a galvanic cell, allowing ion flow without extensive mixing of the diff solutions
Term
 anode   cathode
Definition
 the electrode where oxidation occurs   the electrode where reduction occurs
Term
 Voltaic Cell: cathode reaction   Voltaic Cell: anode reaction
Definition
 mass increases, electrode larger   mass decrease, electrode smaller
Term
 Cell Potential
Definition
 or electromotive Force (emf) the Pull or driving force on the electrons
Term
 Volt and Volt Meter
Definition
 the unit of electrical potential defined as one joule of work per coulomb of charge transferred   an instrument that measures cell potential by drawing electrical current through a known resistance
Term
 Cell Potential
Definition
 a galvanic cell consists of an oxidizing agent in one compartment that pulls electrons through a wire from a reducing agent in the other compartment   the pull or driving force on the electrons is called the cell potential (Ecell) or emf of the cell. unit of electrical potential is the volt V- 1 joule of work per coulomb of charge transferred
Term
 Galvanic cell
Definition
 all half reactions are given as reduction processes in standard tables   when a half reaction is reversed, the sign of Ezero is reversed   when a half reaction is multiplied by an integer, E zero remains the same   a galvanic cell runs spontaneously in the direction that gives a positive value for E zero cell
Term
 Line Notation
Definition
 anode components are listed on the left. Cathode components are listd on the right.   anode and cathode are separated by double vertical lines. a phase difference is indivated by a single vertical line.
Term
 Work
Definition
 work is never the maximum possible if any current is flowing   in any real, spontaneous process some energy is always wasted- the actual work realized is always less than the calculated maximum
Term
 maximum cell potential
Definition
 directly related to the free energy difference between the reactants and the products in the cell   delta G zero = -nFEzero   n=number of moles of electrons F=Faraday= 96,485 coulombs per mole of electrons
Term
 Ion-selective electrodes
Definition
 an electrode senstive to the concentration of a particular ion in solution
Term
 glass electrode
Definition
 an electrode for measuring pH from the potential difference that develops when it is dipped into an aqueous solution containing H+ ions
Term
 Battery
Definition
 a galvanic cell or a group of galvanic cells connected in series, where the potentials of the individual cells added to give the total battery potential
Term
 cathodic protection
Definition
 a method in which an active metal, such as magnesium is connected to steel in order to protect it from corrosion
Term
 corrosion
Definition
 the process by which metals are oxidized in the atmosphere
Term
 electrolysis
Definition
 process that involves forcing a current through a cell to cause a nonspontaneous chemical reaction to occur
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