UMass Amherst CHEM 112 - New Material Final Exam Review (3 pages)

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New Material Final Exam Review



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New Material Final Exam Review

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3
School:
University of Massachusetts Amherst
Course:
Chem 112 - Gen Chem-Sci
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New Material Exam In any chemical process energy must be conserved This is a statement of the law of thermodynamics At what temperatures will a reaction be spontaneous if rH 60 9 kJ and rS 294 J K A Temperatures between 179 K and 235 K B The reaction will be spontaneous at any temperature C All temperatures below 207 K D All temperatures above 207 K E The reaction will never be spontaneous Which one of the following processes involves an increase in the entropy of the system A CaO s CO2 g CaCO3 s B 3 H2 g N2 g 2 NH3 g C 2 Na s Cl2 g 2 NaCl s D N2 g 2 O2 g 2 NO2 g E 2 Ag2O s 4 Ag s O2 g Thermodynamics can be used to determine all of the following EXCEPT A B C D E the temperature at which a reaction is spontaneous the entropy change of a reaction the extent to which a reaction occurs the rate of reaction the direction in which a reaction is spontaneous The standard free energy change for a chemical reaction is 13 3 kJ mol What is the equilibrium constant for the reaction at 117 C R 8 314 J K mol A 0 996 B 1 15E 6 C 1 66E 2 D 60 4 E 7 94E 5 Calculate r G for the reaction below at 25 0 C CS 2 g 3 Cl 2 g S 2 Cl 2 g CCl 4 g given r H 231 1 kJ mol rxn and r S 287 6 J K mol rxn A 145 3 kJ mol rxn B 56 5 kJ mol rxn C 316 9 kJ mol rxn D 518 7 kJ mol rxn E 56 5 kJ mol rxn The following anions can be separated by precipitation as silver salts Cl Br I CrO 4 2 If Ag is added to a solution containing the four anions each at a concentration of 0 10 M in what order will they precipitate Compound AgCl Ag 2 CrO4 AgBr AgI Ksp 1 8E 10 1 1E 12 5 4E 13 8 5E 17 A B C D E gCl Ag 2 CrO 4 AgBr AgI A AgI AgBr AgCl Ag 2 CrO 4 g 2 CrO 4 AgI AgBr AgCl A AgI AgBr Ag 2 CrO 4 AgCl Ag 2 CrO 4 AgCl AgBr AgI New Material Exam If a chemical reaction occurs in a direction that has a positive change in entropy then A the reaction must be exothermic B the change in enthalpy must be negative C heat goes from the system into the surroundings D the reaction must be spontaneous E the disorder of the system increases Assuming the following reaction proceeds in the forward direction 3 Sn 4 aq 2 Cr s 3 Sn 2 aq 2 Cr 3 aq A Sn 4 aq is the reducing agent and Sn 2 aq is the oxidizing agent B Sn 4 aq is the reducing agent and Cr s is the oxidizing agent C Cr s is the reducing agent and Cr 3 aq is the oxidizing agent D Cr s is the reducing agent and Sn 4 aq is the oxidizing agent E Cr s is the reducing agent and Sn 2 aq is the oxidizing agent Write a balanced half reaction for the reduction of CrO 4 2 aq to Cr OH 3 s in a basic solution A B C D E CrO 4 2 aq 4 H 2 O 3 e Cr OH 3 s 5 OH aq CrO 4 2 aq 3 H aq 3 e Cr OH 3 s CrO 4 2 aq 3 OH aq Cr OH 3 s 2 O 2 g CrO 4 2 aq 3 OH aq 3 e Cr OH 3 s 2 O 2 g CrO42 aq 3 H aq Cr OH 3 s 2 e The concentration of Pb 2 in an aqueous solution is 2 49E 3 M What concentration of SO 4 2 is required to begin precipitating PbSO 4 The K sp of PbSO 4 is 2 5E 8 A 1 20E 4 M B 1 00E 5 M C 8 37E 7 M D 9 96E 4 M E 3 17E 3 M Write a balanced chemical equation for the overall reaction represented by the cell notation below Zn s Zn 2 aq H aq H 2 g Pt s A H 2 g Zn s 2 H aq Zn 2 aq B 2H aq Zn s ZnH 2 s C 2H aq Zn s H 2 g Zn 2 aq D H 2 g Zn 2 aq 2 H aq Zn s E 2H aq Zn 2 aq H 2 g Zn s Use the following thermodynamic data Species fH kJ mol S J K mol Fe s 0 0 27 8 O 2 g 0 0 205 1 Fe 3 O 4 s 1118 4 146 4 New Material Exam to calculate S universe for the formation of Fe 3 O 4 s at 298 15 K 3 Fe s 2 O 2 g Fe 3 O 4 s A 3404 J K B 3404 J K C 561 2 J K D 7639 J K E 1162 J K Write a balanced half reaction for the reduction of NO 3 aq to NO g in an acidic solution A NO 3 aq 4 H aq 3 e NO g 2 H 2 O B NO 3 aq 4 H aq NO g 2 H 2 O C NO3 aq 4 e NO g O2 g D NO 3 aq 4 H aq NO g 2 H 2 O 2 e E NO 3 aq 3 e NO g O 2 g


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