Electrochemistry Questions and Answers PDF

1. What is a redox reaction? * A) A reaction where only oxidation occurs. * B) A reaction where only reduction occurs. * C) A reaction where both oxidation and reduction occur. * D) A reaction where no electron transfer occurs. 2. What is oxidation? * A) Gain of electrons * B) Loss of electrons * C...

1. What is a redox reaction? * A) A reaction where only oxidation occurs. * B) A reaction where only reduction occurs. * C) A reaction where both oxidation and reduction occur. * D) A reaction where no electron transfer occurs. 2. What is oxidation? * A) Gain of electrons * B) Loss of electrons * C) Gain of protons * D) Loss of protons 3. What is reduction? * A) Gain of electrons * B) Loss of electrons * C) Gain of protons * D) Loss of oxygen 4. What is an oxidising agent? * A) A species that donates electrons. * B) A species that accepts electrons. * C) A species that is oxidised. * D) A species that increases its oxidation state. 5. What is a reducing agent? * A) A species that accepts electrons. * B) A species that is reduced. * C) A species that donates electrons. * D) A species that decreases its oxidation state. 6. What is the oxidation state of oxygen in O2? * A) -2 * B) -1 * C) 0 * D) +2 7. What is the oxidation state of H in metal hydrides, for example NaH? * A) -2 * B) -1 * C) 0 * D) +1 8. What is the oxidation state of oxygen in peroxides (e.g., H2O2)? * A) -2 * B) -1 * C) 0 * D) +1 9. What is the oxidation state of Cl in ClF3? * A) -3 * B) -1 * C) +1 * D) +3 10. What are the standard conditions for measuring standard electrode potentials? * A) 273 K, 1 atm pressure, 1 mol dm-3 solutions * B) 298 K, 1 atm pressure, 1 mol dm-3 solutions * C) 298 K, 100 atm pressure, 1 mol dm-3 solutions * D) 273 K, 1 atm pressure, 0.1 mol dm-3 solutions 11. What is the standard electrode potential (E°) of the standard hydrogen electrode (SHE)? * A) -1.00 V * B) 0.00 V * C) +1.00 V * D) +2.00 V 12. What is the purpose of the platinum electrode in the SHE? * A) To act as a catalyst * B) To provide an inert surface for the reaction and conduct electricity * C) To react with the hydrogen gas * D) To react with the H+ ions 13. What is the purpose of the salt bridge in an electrochemical cell? * A) To allow the ow of electrons * B) To complete the circuit by allowing the ow of ions. * C) To prevent the two solutions from mixing * D) To provide a source of metal ions fl fl 14. Which of the following is commonly used as a salt bridge? * A) a strip of copper metal * B) a strip of lter paper * C) a solution of saturated potassium nitrate * D) Filter paper soaked in a saturated solution of potassium nitrate 15. In a conventional cell diagram, which half-cell is written on the left- hand side? * A) The half-cell with the more positive E° value * B) The half-cell with the more negative E° value (where oxidation occurs) * C) The half-cell where reduction occurs * D) It doesn't matter 16. What is the conventional representation of an electrochemical cell composed of a zinc electrode in zinc sulfate solution and a copper electrode in copper sulfate solution? * A) Zn2+ | Zn || Cu | Cu2+ * B) Cu2+ | Cu || Zn | Zn2+ * C) Zn | Zn2+ || Cu2+ | Cu * D) Cu | Cu2+ || Zn2+ | Zn 17. How is the standard cell potential (E°cell) calculated? * A) E°(positive electrode) + E°(negative electrode) * B) E°(negative electrode) - E°(positive electrode) * C) E°(positive electrode) - E°(negative electrode) * D) E°(negative electrode) / E°(positive electrode) 18. A spontaneous (feasible) redox reaction has: * A) A negative E°cell value * B) A positive E°cell value * C) An E°cell value of zero * D) It depends on the reaction 19. If E°cell is +0.76 V, what can be said about the feasibility of the overall reaction? * A) The reaction is not feasible. * B) The reaction is feasible. * C) The feasibility cannot be determined from E°cell. * D) The reaction is at equilibrium fi 20. The electrode potentials for two half-cells are: Cu2+ + 2e- -> Cu E° = +0.34 V Zn2+ + 2e- -> Zn E° = -0.76 V What is the standard cell potential (E°cell) for the cell? * A) -1.10 V * B) -0.42 V * C) +0.42 V * D) +1.10 V 21. In an electrochemical cell, where does oxidation occur? * A) At the anode * B) At the cathode * C) In the salt bridge * D) In the external circuit 22. In an electrochemical cell, electrons ow from: * A) Cathode to anode * B) Anode to cathode * C) Positive electrode to negative electrode * D) Solution to electrode 23. What is the electrolyte in a hydrogen fuel cell? * A) sulfuric acid * B) potassium hydroxide * C) sodium chloride * D) Can be an acid or alkali 24. What is the reaction at the negative electrode (anode) in a hydrogen fuel cell operating in *acidic* conditions? * A) O2 + 4H+ + 4e- -> 2H2O * B) H2 -> 2H+ + 2e- * C) 2H+ + 2e- -> H2 * D) 2H2O -> O2 + 4H+ + 4e- 25. What is the reaction at the positive electrode (cathode) in a hydrogen fuel cell operating in *acidic* conditions? * A) O2 + 4H+ + 4e- -> 2H2O * B) H2 -> 2H+ + 2e- * C) 2H+ + 2e- -> H2 * D) 2H2O -> O2 + 4H+ + 4e- fl 26. What is the reaction at the negative electrode (anode) in a hydrogen fuel cell operating in *alkaline* conditions? * A) O2 + 2H2O + 4e- --> 4OH- * B) 2H2O + 2e- --> H2 + 2OH- * C) H2 + 2OH- --> 2H2O + 2e- * D) 4OH- --> O2 + 2H2O + 4e- 27. What is the reaction at the positive electrode (cathode) in a hydrogen fuel cell operating in *alkaline* conditions? * A) O2 + 2H2O + 4e-  User con nue ti WJEC Okay, continuing with the remaining questions for Topic 3.1, REDOX & Electrode Potentials: 27. What is the reaction at the positive electrode (cathode) in a hydrogen fuel cell operating in *alkaline* conditions? * A) O2 + 2H2O + 4e- -> 4OH- * B) 2H2O + 2e- -> H2 + 2OH- * C) H2 + 2OH- -> 2H2O + 2e- * D) 4OH- -> O2 + 2H2O + 4e- 28. What is the overall reaction in a hydrogen fuel cell (in both acidic and alkaline conditions)? * A) 2H2 + O2 -> 2H2O * B) H2 + O2 -> H2O2 * C) H2 -> 2H+ + 2e- * D) O2 + 4H+ + 4e- -> 2H2O  29. What is a major advantage of hydrogen fuel cells over conventional combustion engines? * A) They are cheaper to produce. * B) They produce only water as a waste product (more environmentally friendly). * C) They are more powerful. * D) They use readily available fuels. 30. What is a disadvantage of using hydrogen fuel cells? * A) They produce harmful emissions. * B) Hydrogen gas is dif cult and dangerous to store and transport. * C) They are very inef cient. * D) The technology is very old. Answers and Explanations: 1. C) A reaction where both oxidation and reduction occur. - This is the de nition of a redox reaction. 2. B) Loss of electrons - Oxidation is loss (OIL RIG). 3. A) Gain of electrons - Reduction is gain (OIL RIG). 4. B) A species that accepts electrons. - An oxidising agent causes something else to be oxidised (and is itself reduced). 5. C) A species that donates electrons. - A reducing agent causes something else to be reduced (and is itself oxidised). 6. C) 0 - Elements in their elemental state have an oxidation state of 0. 7. B) -1 - Metals are more electropositive than hydrogen in these compounds. 8. B) -1 - The oxygen-oxygen bond in peroxides results in an oxidation state of -1 for each oxygen. 9. D) +3 - Fluorine is always -1; (3 x -1) + Cl = 0; Cl = +3 10. B) 298 K, 1 atm pressure, 1 mol dm-3 solutions - These are the fi fi fi standard conditions. 11. B) 0.00 V - The SHE is the reference point, de ned as 0.00 V. 12. B) To provide an inert surface for the reaction and conduct electricity - Platinum is unreactive and a good conductor. 13. B) To complete the circuit by allowing the ow of ions. - This maintains charge balance. 14. D) Filter paper soaked in a saturated solution of potassium nitrate Correct answer 15. B) The half-cell with the more negative E° value (where oxidation occurs) - The more negative E° is written on the left (the anode). 16. C) Zn | Zn2+ || Cu2+ | Cu - This is the correct conventional representation. 17. C) E°(positive electrode) - E°(negative electrode) - This is the correct formula. 18. B) A positive E°cell value - A positive E°cell indicates a spontaneous reaction. 19. B) The reaction is feasible. - A positive E°cell value means the reaction is feasible. 20. D) +1.10 V - E°cell = +0.34 V - (-0.76 V) = +1.10 V 21. A) At the anode - Oxidation always occurs at the anode (An Ox). 22. B) Anode to cathode - Electrons ow from where oxidation occurs (anode) to where reduction occurs (cathode). 23. D) Can be an acid or alkali Correct de nition. 24. B) H2 -> 2H+ + 2e- - Hydrogen is oxidised at the anode. 25. A) O2 + 4H+ + 4e- -> 2H2O - Oxygen is reduced at the cathode. fl fi fl fi 26. C) H2 + 2OH- --> 2H2O + 2e- Correct de nition 27. A) O2 + 2H2O + 4e- -> 4OH- - Oxygen is reduced, and water is involved in alkaline conditions. 28. A) 2H2 + O2 -> 2H2O - This is the overall reaction, regardless of the electrolyte. 29. B) They produce only water as a waste product (more environmentally friendly). - This is a key advantage. 30. B) Hydrogen gas is dif cult and dangerous to store and transport. - This is a signi cant challenge for widespread adoption. Powered by pmfm.ai Request Support fi fi fi