Competitive Exams: Chemistry MCQs (Practice-Test 14 of 31)

  1. Consider the following standard reduction potentials, half reactionEo, V I3- (aq) + 2e____> 3I- (aq) 0.53 Cr3 + (aq) + e → Cr2 + (aq) -0.41

  2. Calculate Go (in kJ) for the following reaction at 25oC.

  3. Cr2 + (aq) + I3- (aq) → Cr3 + (aq) + I- (aq)

  4. In which of the following reactions does the oxidation number of the sulfur atom NOT CHANGE?

    1. 3S2- + 8H + + 2NO3- (nitrate ion) → 2NO + 3S + 4H2O

    2. 2SO2 (sulfur dioxide) + O2 → 2SO3 (sulfur trioxide)

    3. 2H2S + 3O2 → 2SO2 (sulfur dioxide) + 2H2O

    4. S8 + 8O2 → 8SO2 (sulfur dioxide)

    5. SO2 (sulfur dioxide) + H2O → H2SO3 (sulfurous acid)

  5. Which of the following reactions IS a reduction-oxidation reaction?

    1. NH3 (aq) + H2O (l) → NH4 + (aq) + OH- (aq)

    2. Cu2 + (aq) + 4NH3 (aq) → Cu (NH3) 42 + (aq)

    3. AgF (s) → Ag + (aq) + F- (aq)

    4. 2Cu + (aq) → Cu2 + (aq) + Cu (s)

    5. 2NO2 (g, nitrogen dioxide) → N2O4 (g, dinitrogen tetroxide)

  6. Which of the following statements explains why a definition of standard state conditions is needed in electrochemistry?

    1. Cell potentials vary with concentration.

    2. Cell potentials vary with temperature.

    3. Cell potentials vary with partial pressures of gases.

    4. Responses a and c are correct.

    5. Responses a, b and c are all correct.

  7. Consider the following reaction and standard cell potential, Ni2 + (aq) + 6NH3 (aq) → Ni (NH3) 62 + (aq), Eo = + 0.25 V Which of the following best describes what would happen in a solution that initially contains 1.0 M Ni2 +, 0.01 M NH3 and 6.0 M Ni (NH3) 62 + at 25oC (Assume that the number of moles of electrons transported in this reaction is equal to 2.)?

    1. The concentrations of both Ni2 + and NH3 would decrease and the concentration of Ni (NH3) 62 + would increase.

    2. The concentrations of both Ni2 + and NH3 would increase and the concentration of Ni (NH3) 62 + would decrease.

    3. The concentration of Ni (NH3) 62 + would decrease, the concentration of NH3 would increase and the concentration of Ni2 + would remain the same.

    4. The concentrations of Ni2 +, NH3 and Ni (NH3) 62 + would all remain the same.

    5. It is impossible to tell.

  8. Consider the following standard reduction potentials, half reactionEo, V Ca2 + + 2e____> Ca-2.76 Pb2 + + 2e → Pb-0.13 Cu2 + + 2e → Cu + 0.34 Hg22 + + 2e → Hg + 0.80 Pt2 + + 2e → Pt + 1.20

  9. Which of the following metals is the strongest REDUCING AGENT?

    1. Ca

    2. Pb

    3. Cu

    4. Hg

    5. Pt

  10. Consider the following standard reduction potentials, half reaction Eo, V Fe2 + + 2e____> Fe-0.4090, Ag + + e → Ag0.7996, O2 + 2H2O + 4e → 4OH- + 0.4010

    1. N/A

    2. N/A

    3. N/A

    4. N/A

  11. Which of the following statements best describes what would happen if a block of silver metal were connected to a buried iron pipe via a wire (i.e.. as in a cathodic protection process).

    1. The silver metal would corrode, a current would be produced in the wire, and O2 would be reduced on the surface of the iron pipe.

    2. The silver metal would corrode, a current would be produced in the wire, and Fe2 + would be reduced on the surface of the iron pipe.

    3. The iron pipe would corrode, a current would be produced in the wire, and Ag + would be reduced on the surface of the silver metal.

    4. The iron pipe would corrode, no current would be produced in the wire, and O2 would be reduced on the surface of the iron pipe.

    5. Neither the iron pipe nor the silver metal would be oxidized but O2 would be reduced.

  12. Consider the following reduction-oxidation reaction, Zn (s) + Cu2 + (aq) → Cu (s) + Zn2 + (aq), Eo = + 1.10 V When the components of the two half-reactions involved in this reaction are correctly separated, this reaction can be used to do electrical work and the change in internal energy of the system decreases. Which of the following statements best describes what will happen if Zn (s) is added to a solution containing Cu2 + (aq) at constant volume at 25oC?

    1. The reaction will occur and the temperature of the solution will increase.

    2. The reaction will occur and the temperature of the solution will decrease.

    3. The reaction will occur and the temperature of the solution will remain the same.

    4. The reaction will not occur and the temperature of the solution will remain the same.

    5. The reaction will not occur but the temperature of the solution will increase.

  13. Using the following standard reduction potentials, half reactionEo, V Cl2 + 2e____> 2Cl- + 1.36 Cr3 + + 3e → Cr-0.74

  14. calculate Go (in kJ) for the reaction, 3Cl2 + 2Cr → 6Cl- + 2Cr3 + Use the following information to answer the next four (4) questions.

    1. N/A

    2. N/A

    3. N/A

    4. N/A