Chem 112 Exam , Av = 45.2, Med = 45, s = 17.1

Transcription

1 hem xam 3 07, Av = 45., Med = 45, s =

2 DO NOT OPN THIS XAM UNTIL YOU AR INSTRUTD TO DO SO Please print your name on the scantron o Last Name, First Name o That s all that s needed Sit in odd numbered seats. Books & Bags in the front of the room. No text entry calculators. Use the exams as scratch paper. Keep the exams when you are done. Turn in the scantrons. 00 total points. Questions -8 worth 5.5 points each. Question 9 worth point.

3 onstants R = 8.34 J/K-mol R = 0.08 l-atm/k-mol mole = 6.0 x 0 3 Faraday = 96,500 coulombs hem quations Gas quations (P+(n a/v ))(V nb)=nrt PV = nrt q = m s (T) u = 3RT M Pythagorean Theorem: a + b = c Volume of a cube: V = l 3 Henry s Law lausius-lapeyron quation S = khp H P vap P H vap ln b ln P R T T RT olligative Properties = MRT PA = PA 0 XA P = PA 0 XB Tb = Kbcm Tf = Kfcm hemical Kinetics ln[ ] kt ln[ A A t ] 0 [ ] A t kt [ A ] 0 Arrhenius quation k = A (e a RT) k ln k a R T T hemical quilibrium aa + bb = c + dd K c [ ] [ D] a [ A] [ B] d b K p K ( RT ) c n ph ph = - log [H + ] antilog(x) = 0 x px = - log X KaKb = Kw Henderson-Hasselbach qn ph pk a [ base] log [ acid ] Quadratic formula ax bx c 0 b x b 4ac a hemical Thermodynamics U q w w PV G H TS ln ( K ) = H 0 rxn ( ) G G 0 RT ln Q K R T T lectrochemistry cell cathode anode G 0 RT ln K Nersnt quation cell 0 cell RT ln Q nf G 0 nf cell At 98K cell 0 cell log Q n 3

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5 ] The equilibrium constant is given for two of the reactions below. Determine the value of the missing equilibrium constant. A(g) + B(g) AB(g) Kc =? AB(g) + B(g) AB(g) Kc = 6.4 A(g) + B(g) AB(g) Kc = 8. A).8 B) ) 0.58 D) 46 ).7 ] What is Δn for the following equation in relating Kc to Kp? A) 3 B) - ) - D) ) NO4(g) NO(g) 3] onsider the following reaction: H4(g) + HS(g) S(g) + 4 H(g) A reaction mixture initially contains 0.50 M H4 and 0.75 M HS. If the equilibrium concentration of H is 0.44 M, which of the following will allow you to find the equilibrium constant (Kc) for the reaction. 3 a] K c = b] K c = x(4x) 4 (0.50 x)(0.75 x) x(4x) 4 (0.50 x)(0.75 x) where x = 0.44 where x = 0. c] K c = x(4x) (0.50 x)(0.75 x) where x = 0. d] K c = e] K c = x(x) 4 (0.50 x)(0.75 x) x(x) 4 (0.50 x)(0.75 x) where x = 0.44 where x = 0. 5

6 4] onsider the following reaction at equilibrium. What effect will increasing the temperature have on the system? 4 3H8(g) + 5 O(g) 3 O(g) + 4 HO(l) ΔH = -0 kj A) The reaction will shift to the left in the direction of reactants. B) The reaction will shift to the right in the direction of products. ) The equilibrium constant will increase. D) The equilibrium constant will decrease. ) No effect will be observed. 5] Which of the following species is amphoteric? 5 A) O3 - B) HF ) NH4+ D) HPO4 - ) None of the above are amphoteric. 6] alculate the ph of a solution that contains M OH at 5. 6 A).8 B) 5. ).7 D) 8.89 ) ] Which of the following is a weak base? 7 A) NH(H3) B) N ) NaOH D) HH ) None of the above are weak bases. 8] alculate the ph of a buffer that is 0.5 M HH3O and 0.6 M KH3O. The Ka for HH3O is A) 4.89 B) 9. ) 4.60 D) 9.6 )

7 9] Which of the following will allow the calculation the ph when 5.0 ml of 0.00 M acetic acid (HA) is mixed with 5.0 ml of 0.00 M NaOH. Ka =.8 x a] (mol OH - added) = (mol acid) therefore ph = 7.00 b] (mol OH - added) = (mol acid) therefore use ph pk a [ base] log [ acid ] c] (mol OH - added) = (mol acid) therefore use A - + HO HA + OH - d] (mol OH - added) > (mol acid) the ph is pka e] (mol OH - added) < (mol acid) the ph is ½ pka. 0] If the solubility of AgrO4 in water is 6.3 x 0-5 M the Ksp for this compound is, 0 A).0 x 0 - B) 5.0 x 0 - ) 3.0 x 0-3 D).6 x 0-3 ) 9. x 0-7 ] If the pka of HHO is 3.74 and the ph of an HHO/NaHO solution is 3., which of the following is true? A) [HHO] < [NaHO] B) [HHO] = [NaHO] ) [HHO] << [NaHO] D) [HHO] > [NaHO] ) [HHO] = ½ [NaHO] ] Which of the following is true for a spontaneous process? A) Hsys > 0 & Suniv = Ssys + Ssurr = 0 B) Δuniv = Δsys + Δsurr = 0 & Suniv = Ssys + Ssurr > 0 ) Δuniv = Δsys + Δsurr > 0 & Suniv = Ssys + Ssurr > 0 D) Δuniv = Δsys + Δsurr > 0 & Suniv = Ssys + Ssurr = 0 ) Δuniv = Δsys + Δsurr = 0 & Suniv = Ssys + Ssurr < 0 7

8 3] is a thermodynamic function that increases with the number of energetically equivalent ways to arrange components of a system to achieve a particular state. 3 A) Heat of reaction B) Free energy ) ntropy D) nthalpy ) Molar equivalence 4] Place the following in order of increasing entropy at 98 K. 4 H6(g), Pb(s), Mg(s), H4(g) A) Mg, Pb, H6, H4 B) H6, H4, Pb, Mg ) Pb, Mg, H4, H6 D) Mg, Pb, H4, H6 ) Pb, Mg, H6, H4 5] For the following example, identify the following. 5 HO(l) HO(g) A) a negative ΔH and a negative ΔS B) a positive ΔH and a negative ΔS ) a negative ΔH and a positive ΔS D) It is not possible to determine without more information. ) a positive ΔH and a positive ΔS 6] Determine the equilibrium constant for the following reaction at 98 K. 6 l(g) + O3(g) lo(g) + O(g) ΔG = kj A). 06 B) ) D) )

9 7] onsider the following reaction at constant P. Use the information here to determine the value of ΔSsurr at 98 K. Predict whether or not this reaction will be spontaneous at this temperature. 7 N(g) + O(g) NO(g) ΔH = kj A) ΔSsurr = +3 J/K, reaction is not spontaneous B) ΔSsurr = -656 J/K, reaction is spontaneous ) ΔSsurr = -3 J/K, reaction is not spontaneous D) ΔSsurr = kj/k, reaction is not spontaneous ) ΔSsurr = J/K, it is not possible to predict the spontaneity of this reaction without more information. 8] Which Br nsted-lowry acid is not considered to be a strong acid in water? 8 A) HI B) HBr ) HSO3 D) H NO3 ) Hl 9] My recitation meets at a) :30 pm on Thursdays b) blank c) blank d) :30 pm on Thursdays 9

10 Answers 3 B Kc = A 5 D 6 D 7 A A x = 6.3e-5; (x)x = Ksp =.0e- D B 3 4 D 5 6 A 7 8 0