PiQ Final Exam

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Chemistry

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Review Test Submission: Additional Practice Final Exam Remix (with feedback) Sp 2021 2021SP-22142-CHEM1332-Fundamentals of Chemistry 2 Course Content Folders Pace Incentive Quizzes (PiQ's) Review Test Submission: Additional Practice Final Exam Remix (with feedback) Sp 2021 User Course 2021SP-22142-CHEM1332-Fundamentals of Chemistry 2 Test Additional Practice Final Exam Remix (with feedback) Sp 2021 Started 5/2/21 11:30 PM Submitted 5/3/21 12:22 AM Status Completed Attempt Score 23.66666 out of 35 points Time Elapsed 52 minutes out of 1 hour and 43 minutes Instructions Results Displayed Submitted Answers, Correct Answers, Feedback If an image doesn't appear, try reloading the question. For multiple choice questions, select the best answer from those provided. Follow the rules of signiÑcant Ñgures in calculations; round to the correct number of sig Ñgs at the end unless the question speciÑes otherwise. NOTE: in questions where a logarithmic value (pH, POH, pKa, log, etc.) is calculated, express your answer with 2 decimal places. Some questions may ask you to put your answer in scientiÑc notation. This must be done as E-notation. Thus, 1321 would be entered as 1.321E3; 0.00123 would be 1.23E-3. WARNING: You must enter answers with exponents by using uppercase “E” rather than lowercase “e”; for example, 1.23E-22 rather than 1.23e-22. Your numerically correct answers might be marked as incorrect by Bb if you use lowercase “e”. proton mass = 1.67262 x 10 -27 kg or 1.00728 amu, neutron mass = 1.67493 x 10 -27 kg or 1.00866 amu, 1 amu = 1.66056 x 10 -27 kg = 931.5 MeV/c 2 Question 1 Library Writing Center Launch Home 1 out of 1 points

Selected Answer: Correct Answer: Response Feedback: Use VSEPR theory to predict the molecular geometry of XeF 4 . square planar square planar Practice Exam 2 1a Practice Exam 2 1a Question 2 Selected Answer: [None Given] Correct Answer: 6.82E2 ± 2% Response Feedback: A 252.9 mL sample of an aqueous solution at 25°C contains 78.3 mg of an unknown nonelectrolyte compound. If the solution has an osmotic pressure of 8.44 torr, what is the molar mass (in g/mol) of the unknown compound? Enter your value with three signiÑcant Ñgures . Recall that the equation for osmotic pressure looks very similar to the ideal gas equation. Π V=nRT . WIth the given information you can Ñrst solve for n to obtain the moles of the compound. Then since you know both the mass and the moles of the compound you can calculate the molar mass. Question 3 Selected Answer: Correct Answer: Response Feedback: Which one of the following substances would be the least soluble in cyclohexane, C 6 H 12 ? K 3 PO 4 K 3 PO 4 "Like prefers like. " Since cyclohexane, C 6 H 12 , is a nonpolar molecule, substances that are very polar will not dissolve. An ionic substance is extremely polar due to the charges associated with its cations and anions. Question 4 Experimental Initial A Initial B Initial rate Trial (M) (M) (M s -1 ) 1 0.15 0.30 0.000701 2 0.30 0.30 0.000701 3 0.15 0.15 0.000175 4 0.45 0.45 0.001578 Suppose you have measured the kinetics of the reaction, 2 A + B C + 2 D at room temperature using the method of initial rates. A table summarizing the results of four diÖerent experimental trials is shown below: First determine the orders of [A] and [B] in the rate law. Then based on these data and your rate law, what is the value of the rate constant k (in units of M -1 s -1 ). {Enter your value with three signiÑcant Ñgures.} 0 out of 1 points 1 out of 1 points 1 out of 1 points

Selected Answer: 0.00779 Correct Answer: 0.007794349 Answer range +/- 0.002 (0.005794349 - 0.009794349) Response Feedback: The rate law can be found to be rate = k [B] 2 , the known values in a trial can be substituted, and the value of k can be calculated. Question 5 SpeciÑed Answer for: a half SpeciÑed Answer for: b zero SpeciÑed Answer for: c second Correct Answers for: a Evaluation Method Correct Answer Case Sensitivity Exact Match half Exact Match square root Correct Answers for: b Evaluation Method Correct Answer Case Sensitivity Exact Match zero Exact Match zeroth Correct Answers for: c Evaluation Method Correct Answer Case Sensitivity Exact Match zero Exact Match zeroth Response Feedback: Given a mechanism consisting of the following two elementary steps: A (g) 2 B (g) fast equilibrium B (g) 2 C(g) slow step write the rate law of the rate determining step, and then use the equilibrium condition to eliminate any intermediates. Give the orders of the following substances which appear in the overall reaction: {A} is [a] order. {B} is [b] order. {C} is [c] order. For example, zero, half, Ñrst, second, third, etc. (If it is negative, you would write, negative Ñrst, negative second, etc) 1. Write rate law of slow step. 2. Write equilibrium expression and solve for intermediate (in this case B). 3. Substitute into rate law to remove B from Ñnal rate law. 4. Write orders of each substance. Question 6 Experimental Initial A Initial B Initial rate Trial (M) (M) (M s -1 ) 1 0.15 0.30 0.000857 2 0.30 0.30 0.001714 3 0.15 0.15 0.000428 4 0.45 0.45 0.003856 Suppose you have measured the kinetics of the reaction, 2 A + B C + 2 D at room temperature using the method of initial rates. A table summarizing the results of four diÖerent experimental trials is shown below: First determine the orders of [A] and [B] in the rate law. 0.66666 out of 1 points 1 out of 1 points

Selected Answer: 0.0190 Correct Answer: 0.019039615 Answer range +/- 0.002 (0.017039615 - 0.021039615) Response Feedback: Then based on these data and your rate law, what is the value of the rate constant k (in units of M -1 s -1 ). {Enter your value with three signiÑcant Ñgures.} The rate law can be found to be rate = k [A] [B], the known values in a trial can be substituted, and the value of k can be calculated. Question 7 Selected Answer: -7.80E2 Correct Answer: 7.80E2 ± 4 Response Feedback: The rate constant for a reaction is measured as a function of time. A plot is created by graphing ln(k) on the y-axis and 1/T on the x-axis, and a best Ñt line wit R= 8.314 J/(K mol) Enter your value with three signiÑcant Ñgures. (with R = 8.314 J/(K mol), E in J. Convert the Ñnal answer to kJ/mol. For additional help see: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical Question 8 The reaction energy diagram below represents a two step reaction mechanism. 0 out of 1 points 1 out of 1 points

SpeciÑed Answer for: z C SpeciÑed Answer for: x D Correct Answers for: z Evaluation Method Correct Answer Case Sensitivity Exact Match C Correct Answers for: x Evaluation Method Correct Answer Case Sensitivity Exact Match D Response Feedback: To determine the activation energy of the second step in the reaction , the energy of species [z] would be subtracted from the energy of species [x] . Enter the letter that represents the appropriate chemical species. The diÖerence D-C in this diagram represents the activation energy of the second step of the reaction. For further information see: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chem Question 9 Selected Answer: 1.71E-27 Correct Answer: 1.710000000000000000000000000E27 ± 2% Response Feedback: At a given temperature, the K eq for the equilibrium below is 4.14 × 10 13 . 2NO (g) + O 2 (g) 2NO 2 (g) What is the value of K eq at this temperature for the following reaction? 4NO (g) + 2O 2 (g) 4NO 2 (g) If you multiply an equation by a number, you raise the equilibrium constant the the power of that number. Question 10 Selected Answer: 6.42E-7 Correct Answer: 6.42E-7 ± 2% Response Feedback: The reaction below has a K p value of 4.2 x 10 -5 . What is the value of K c for this reaction at 797 K? 2 SO 3 (g) 2 SO 2 (g) + O 2 (g) , with R = 0.0821 atm L / (mol K) and T in K. Question 11 Selected Answer: B. Correct Answer: B. Response Feedback: A 10.0-g sample of solid NH 4 Cl is heated in a 5.00-L container to 900°C. At equilibrium the pressure of NH 3 ( g ) is 1.52 atm. NH 4 Cl( s ) NH 3 ( g ) + HCl( g ) The equilibrium constant, K p , for the reaction is: 2.31. 2.31. Notice the amount of solid does not enter the calculation since the equilibrium is heterogeous. Question 12 0 out of 1 points 1 out of 1 points 1 out of 1 points 1 out of 1 points

Selected Answer: E. Correct Answer: E. Response Feedback: I. Increasing the temperature II. Decreasing the temperature III. Increasing the volume IV. Decreasing the volume V. Removing some NH 3 VI. Adding some NH 3 VII. Removing some N 2 VIII. Adding some N 2 Consider the following system at equilibrium: N 2 ( g ) + 3H 2 ( g ) 2NH 3 ( g ) with ∆H= -92.94 kJ. Which of the following changes will shift the equilibrium to the right? II, IV, V, VIII II, IV, V, VIII I. Because the reaction is exothermic, when heat is added by increasing the temperature the reaction shifts left. II. Because the reaction is exothermic, when heat is removed by decreasing the temperature the reaction shifts right . III. Because there are more moles of reactants than products, increasing the volume favors the side with more moles of gas, which in this case shifts left. IV. Because there are more moles of reactants than products, decreasing the volume favors the side with fewer moles of gas, which in this case shifts right. V. Removing a product (NH 3 ) shifts the reaction right. VI. Adding a product (NH 3 ) shifts the reaction left. VII. Removing a reactant (N 2 ) shifts the reaction left. VIII. Adding a reactant ( N 2 ) shifts the reaction right. Question 13 Selected Answer: [None Given] Correct Answer: 8.09 ± 0.02 Response Feedback: At 25º C, what is the pH of a 0.111 M aqueous solution of potassium Òuoride (KF) given that the K a of hydroÒuoric acid (HF) is 7.24 x 10 -4 . Enter your answer in decimal format with two decimal places (value ± 0.02). Practice exam 2 9 Practice exam 2 9 Question 14 Use the following table of data in answering the question below the table: Acid Name Formula pK a pK b Conjugate Base Hydrofluoric acid HF 3.17 10.83 F - Nitrous acid HNO 2 3.25 10.75 NO 2 - 0 out of 1 points 0 out of 1 points

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