Chem 2, exam 2 study guide
Chem 2, exam 2 study guide Chm2046
Popular in General Chemistry 2
Popular in Chemistry
This 4 page Study Guide was uploaded by Andrew Faus on Sunday October 25, 2015. The Study Guide belongs to Chm2046 at University of North Florida taught by Cristos Lampropolous in Fall 2015. Since its upload, it has received 126 views. For similar materials see General Chemistry 2 in Chemistry at University of North Florida.
Reviews for Chem 2, exam 2 study guide
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/25/15
Equilibrium No reaction goes to 100 completion all reactions are reversible When in equilibrium its forward and reverse rates are equal equilibrium can be expressed as Kc Equilibrium constant which is equal to the concentration of products to the power of their coefficients over the concentration of the reactants to the power of their coefficients If aA bB ltgt CC dD then Kc CquotcDquotdAquotaBquotb lf K is very large this means the rxn favors the products and moves to quotcompletionquot lf K is very small this means the rxn favors the reactants and gives quotno reactionquot Q is the quotquotientquot of the reaction rxn at any point in a rxn Q can be compared with K to determine where in relation to equilibrium the rxn lies Qc uses the same equation used for Kc above but remember it is not equilibrium unless QK lf Q lt K then the reaction favors the products proceeds left to right If O gt K then the reaction favors the reactants proceeds right to left K can also be expressed in terms of pressure remember that PV nRT PressureVolume molesldeal gas constantTemperature Thus we can derive the following Kp KcRT Deltan Deltanmoles of products moles of reactants R00821 LatmmolK T is expressed in Kelvin Kc can be used to solve equilibrium problems using an ICE table Initial concentration Change in concentration Equilibrium concentration Rxn aA bB ltgt CC dD 391 A B C D C ax bx cx dx Make sure to multiply x by the respective coefficient E A x B x Cx DX and remember Kc CquotcDquotdAquotaBquotb Equilibrium concentrations can be used to calculate Kc and vice versa It is good to find practice problems that ask you to work in both directions In some cases the quadratic formula is needed to solve the problem to do this put the formula in the form of aXA2 bx c O and use x b or Sq rtbquot2 4ac2a In some cases the size of x is quotnegligiblequot and an approximation can be used to avoid using the quadratic equation when approximating eliminate any x or x39s from the equation and cross multiply to solve To test the legitimacy of the approximation find x and run this test xlnitial concentration x 100 lt 5 If this is true the approximation is ok to use if not then solve the problem again with the quadratic equation When the reaction Equation changes K changes If the reaction is written in the opposite direction use the inverse of K 1K If there is more than one step only worry about the overall reaction lf coefficients are multiplied by a common factor use K to the power of the common factor If the reaction contains liquids or solids do not include them in the K equation Le Chatlier39s Principle The equilibrium of a rxn can be disturbed in 3 ways Additionremoval of products or reactants adding products will shift the rxn towards the reactants adding reactants will shift the rxn towards the products removing will do the opposite Change in Temperature see Van39t Hoff below if DeltaH is endothermic treat heat as a reactant if DeltaH is exothermic treat heat as product use the results from additionremoval of products to decide how the change effects K Change in volume if there is an unequal number of moles on each side If Volume increases the rxn will favor the direction that reduces pressure and vice versa The Van39t Hoff equation is a mathematical expression of the affect a change in temperature has on the K of a rxn lnK2K1 DeltaHR1T21T1 Catalysts do no affect equilibrium The Haber Process Use of an apparatus to transform N and H into NH3 by pushing the equilibrium of the rxn to the right NH3 is constantly removed as a liquid NH3 is used as fertilizer so the Haber process if very important to agriculture AcidBase Equilibria Acids and Bases have several different definitions according to different scientists the most commonly used definition is the Arrehenius definition which tells us that An Acid increases the level of H in a solution A Base increases the level of OH in a solution Strong Acids and Bases react to give a salt water which results in the net ionic equation H OH gt H20 Notice it is unidirectional because of 100 dissocitation Strong acids include HCl HBr Hl HClO4 HNOB H2804 Strong Bases include LiOH NaOH KOH RbOH CsOH CaOH2 SrOH2 BaOH2 Weak acids and Weak bases however do not fully dissociate We measure their strength by using Dissociation constants Ka and Kb Acid Dissociation Constant Ka AHHA Base Dissociation Constant Kb AOHAOH Most weak bases have N note that as the Ka of a certain acid increases its Kb will decrease We known that the Dissociation constant of water is 1OA14 so remember the following KaKbKw Kw10quot 14 Thus if we are given Ka or Kb of a certain acid or base we can find the other The p scales Remember that a p in front of something just means we are taking the negative log of it For example pH logH and pOH logOH Also remember that pHpOH14 On the pH scale Acid lt 7 lt Base This is reversed on the pOH scale The BronstedLowry Definition of Acids and Bases Acids are H donors Bases are H acceptors This leads to the concept of conjugate bases An acid has a conjugate base and a base has a conjugate acid For an Acid its conjugate base is the anion version with one less H Thus it is now capable of accepting an H making it a BL base For a Base its conjugate acid is the cation with one more H Thus it is now capable of donating an H making it a BL acid For example H28 NH3 ltgt HS NH4 H2S acid it donates an H HS is its conjugate base it can now accept an H NH3 base it accepts an H NH4 is its conjugate acid it can now accept an H We can predict the direction of a rxn using the Ka or Kb of an acid or base Reactions will move in the direction of equilibrium the pH at equilibrium is dependent on the reactants The reactants could be strong acid strong base 100 dissociation Neutral pH weak acid strong base pHgt7 more basic strong acid weak base pHlt7 more acidic weak acid weak base pH could be acidic or basic depending on Ka and Kb Using the Ka one can find the concentration of H ions and vice versa Given the pH or pOH one can find the H concentration To get the H from pH taken the antilog of the negative H 10quotH Use the ICE table and remember the equations from earlier Acid Dissociation Constant Ka AHHA Base Dissociation Constant Kb AOHAOH Approximations Because the change x is often negligible one can approximate and eliminate any x or xs from the equation avoiding the quadratic formula However this approximation must be tested Remember the test This test is used to calculate ionization if it is less than 5 the approx is good if xinitialx100 lt 5 than the approximation is ok if not then use the quadratic equat What is being calculated here Concentration dissociatedlnitial Concentrationx100 ionization Saltsaq Salts consist of cations and anions As is known some catanions have different charges electronegativity and etc Thus salts produce basic acidic or neutral solutions when dissolved Neutral solutions are only produced by a strong base cationstrong acid anion combo Strong base cations include Na K Li Rb Cs Ca2 Sr2 Ba2 Strong acid anions include Cl Br l N03 ClO4 There are three ways in which an Acidic solution can form 1 The anion of a strong acid and the cation of a weak base The anion will not interact with the water but the cation will increasing H 2 A complex ion this can increase H 3 Salts which contain H2PO4 it is a weak acid Basic solutions can only form in the opposite way of 1 from above weak acid anion strong base cation Cation doesn39t react with H20 anion is a weak base and increases OH Remeber the aciditybasicity of a solution is judged by KaKb lf Ka lt Kb then the solution is basic lf Ka gt Kb then the solution is acidic Polyprotic AcidsBases Poly many These AcidsBases can lose or pick up multiple H cations Each addition H adds to the Ka value and each additional H is more difficult check example in Powerpoint Acids and Bases Lewis Definition an acid can accept an electron pair a base can donate an electron pair Combing a Lewis acid and Lewis base forms a Lewis adduct Common Ion Effect As stated in Le Chatelier39s principle adding or removing a reactant or product will shift the equilibrium of a reaction In the case of acidsbases this changes the pH When given the molarity of an acid and a salt within the acid that has a common ion the H can be determined HF and NaF have a common ion of F If given the initial concentration of HF and and NaF one knows the initial concentration of F and can use this in the ICE table along with the initial concentration of HF This can be placed into the Ka equation to determine the H and then later used to determine the ooionization Buffers Info Will be added on 1026 email me if you would like the updated version N00895209 unfedu Andrew
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'