UNIT 9: Solutions and Gases Lesson 9.2: Redox Reactions By the end of today, you will have an answer to: How do we determine if a reaction is a redox reaction? Do Now: 1. Which compound has both ionic and covalent bonding? (1) CaCO 3 (2) CH 2Cl 2 (3) CH 3OH (4) C 6H 12O 6 2. Which statement describes the particles of an ideal gas based on the kinetic molecular theory? (1) The gas particles are arranged in a regular geometric pattern. (2) The gas particles are in random, constant, straight-line motion. (3) The gas particles are separated by very small distances, relative to their sizes. (4) The gas particles are strongly attracted to each other. 3. Under which conditions of temperature and pressure would a 1-liter sample of a real gas behave most like an ideal gas? (1) 100 K and 0.1 atm (2) 100 K and 10 atm (3) 500 K and 0.1 atm (4) 500 K and 10 atm 4. Which type of energy is associated with the random motion of the particles in a sample of gas? (1) Chemical energy (2) Electromagnetic energy (3) Nuclear energy (4) Thermal energy 5. The particles in which sample of LiCl(s) have the same average kinetic energy as the particles in a 2.0-mole sample of H 2O(l) at 25 C? (1) 1.0 mol at 75 C (2) 2.0 mol at 50 C (3) 3.0 mol at 25 C (4) 4.0 mole at 0 C 6. Which rigid cylinder contains the same number of gas molecules at STP as a 2.0-liter rigid cylinder containing H 2(g) at STP? (1) 1.0-L cylinder of O 2(g) (2) 2.0-L cylinder of CH 4(g) (3) 1.5-L cylinder of NH 3(g) (4) 4.0-L cylinder of He(g) LEO the lion says GER How do you identify a redox reaction? 1. Assign oxidation states to each atom 2. If oxidation states change from reactant to product, a redox reaction has occurred! Can oxidation occur without reduction??? Why?
Example 1: F2 + 2Cl - Cl2 + 2F - Step 1: Determine the oxidation state of each element on the reactant and product side. Step 2: Ask the following questions- 1. Did any of the oxidation states change from the reactant side to the product side? 2. Which element was reduced? 3. Which element was oxidized? 4. So, is this a REDOX reaction? 5. What is the half reaction for oxidation? Lose electrons oxidation 6. What is the half reaction for reduction? Gain electrons reduction New Terms: Reducing Agent Definition: In the example above: Oxidizing Agent Definition: In the example above: Example 2: 2H2 + O2 2H2O 6. What is the half reaction for oxidation? 7. What is the half reaction for reduction? Example 3: ZnBr 2 + 2 HCl ZnCl 2 + 2 HBr
9.2 Classwork: Redox Reactions Example 4: 2K + Ca 2+ Ca + 2K + 6. What is the half reaction for oxidation? 7. What is the half reaction for reduction? Example 5: Zn + 2HCl ZnCl 2 + H 2 6. What is the half reaction for oxidation? 7. What is the half reaction for reduction? REGENTS PRACTICE: 1. All redox reactions involve (1) the gain of electrons only (2) the loss of electrons only (3) both the gain and the loss of electrons (4) neither the gain nor the loss of electrons Is this a redox reaction? Why or why not? (Hint: Write down oxidation states for each atom) 2 Mg + O2 2MgO 3. Did any of the oxidation states change from the reactant side to the product side? a. 4. Which element was reduced? 5. Which element was oxidized? 6. What is the reducing agent? 2. A redox reaction is a reaction in which (1) only reduction occurs (2) only oxidation occurs (3) reduction and oxidation occur at the same time (4) reduction occurs first and then oxidation occurs 2Na + Br2 2NaBr 8. Is this a REDOX reaction? 9. What is being reduced? 10. What is being oxidized? 11. What is the reducing agent? 12. What is the oxidizing agent? 7. What is the oxidizing agent?
13. Co + Pb 2+ Co 2+ + Pb --Write the half reactions for oxidation: --Write the half reaction for reduction: 14. Ca + Co 2+ Co + Ca 2+ --Write the half reactions for oxidation: --Write the half reaction for reduction: 15. Li + NaCl Na + LiCl Redox? yes or no oxidation: reduction: oxidizing agent: reducing agent half reaction for oxidation: 16. NaCl + LiCl NaCl + LiCl Redox? yes or no oxidation: reduction: oxidizing agent: reducing agent half reaction for oxidation: half reaction for reduction: half reaction for reduction: Regents-Style Practice 17. Which balanced equation represents a redox reaction? 18. Given the balanced equation representing a redox reaction: 19. In a redox reaction, how does the total number of electrons lost by the oxidized substance compare to the total number of electrons gained by the reduced substance? (1) The number lost is always greater than the (2) The number lost is always equal to the number gained (3) The number lost is sometimes equal to the (4) The number lost is sometimes less than the 20. Given the balanced equation representing a reaction:
9.2 Homework: Redox Reactions More PART A Practice!