mccord exam 2 solutions

mccord exam 2 solutions - Version 142 Exam 2 McCord(52405...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Version 142 – Exam 2 – McCord – (52405) 1 This print-out should have 29 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. Make sure you are taking the right exam. This is Dr. McCord’s 10AM CH302 course with unique 52405. McCord 10am 001 10.0 points What happens to the concentration of NO(g) when the total pressure on the equilib- rium reaction 3 NO 2 (g) + H 2 O( ) 2 HNO 3 (aq) + NO(g) is increased (by compression)? 1. Unable to determine 2. decreases 3. increases correct 4. remains the same Explanation: Increasing the total pressure on the sys- tem by decreasing its volume will shift the equilibrium toward the side of the reaction with fewer numbers of moles of gaseous com- ponents. If the total number of moles of gas is the same on the product and reactant sides of the balanced chemical equation, then changing the pressure will have little or no ef- fect on the equilibrium distribution of species present. The amount and concentration of NO will increase. 002 10.0 points If Δ G rxn is positive, then the forward reaction is (spontaneous / nonspontaneous) and K is (less / greater) than one. 1. nonspontaneous; greater 2. spontaneous, less 3. spontaneous, greater 4. None of these; Δ G is not directly related to K . 5. nonspontaneous; less correct Explanation: A positive Δ G rxn (standard reaction free energy) denotes an endothermic reation, which is nonspontaneous. Also, Δ G rxn = - RT ln K , so a positive Δ G rxn would result in a K that is between the values of zero and one. 003 10.0 points A weak acid (HA) is found to ionize 17% when mixed at a concentration of 0 . 38 mol/L. What is the value of K a for this acid? 1. 0.00952941 2. 0.00994147 3. 0.0170042 4. 0.00967314 5. 0.0266667 6. 0.00935926 7. 0.00483024 8. 0.0132313 9. 0.00678571 10. 0.00555464 Correct answer: 0 . 0132313. Explanation: 0 . 17(0 . 38) = 0 . 0646 . You must also subtract that amount from the original concentration, too: 0 . 38 - 0 . 0646 = 0 . 3154 K a = (0 . 0646) 2 0 . 3154 = 0 . 0132313 . 004 10.0 points 100 mL of 0.50 M BaCl 2 is added to 100 mL of 0.50 M HCl. Which of the following equations is the correct charge balance for this system? 1. 2[Ba 2+ ] = [Cl ] 2. 2[Ba 2+ ] + [H + ] = 2[OH ] + 2[Cl ]
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Version 142 – Exam 2 – McCord – (52405) 2 3. 2[Ba 2+ ] + [H + ] = 2[OH ] + [Cl ] 4. [Ba 2+ ] + [H + ] = 3[Cl ] 5. 2[Ba 2+ ] + [H + ] = [OH ] + [Cl ] correct 6. [Ba 2+ ] = 2[OH ] 7. [Ba 2+ ] + [H + ] = [OH ] + [Cl ] Explanation: 005 10.0 points Consider the statements Z1) A 0.05 M HCl solution has the same pH as 0.05 M HCN. Z2) A 0.10 M solution of a weak acid has the same pH as a 0.10 M solution of a weak base that has the same ionization constant. Z3) A solution in which pH equals pOH must be neutral. Z4) An acidic solution contains H 3 O + but no OH , while a basic solution contains OH but no H 3 O + . Which response includes all the above statements that are true? 1. Z2 and Z4 only 2. None of these is correct. 3. Z1 and Z3 only 4. Z1 and Z4 only 5. Z3 only correct Explanation: HCl is a strong acid which completely disso- ciates in aqueous solution but HCN is a weak acid which only partially ionizes in solution.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern