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Chemistry Mole Practice Questions & Oxidation-Reduction Rules

Practice balancing chemical equations using the mole concept. Understand oxidation and reduction rules for atoms and ions in compounds.

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Chemistry Mole Practice Questions & Oxidation-Reduction Rules

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  1. Warm Up What does LEO says GER stand for? What happens to the reactant side of a chemical equilibrium when the product side is decreased?

  2. Announcements • Final exam tomorrow! • Unit 10 quiz on Friday!

  3. Take 1

  4. How To Use The Mole: Balance the Equation to answer the questions! • __H2(g) + __O2(g) __H2O(l) • If you have 2 moles of H2, how many moles of H2O will you produce? • If you have 4 moles of H2, how many moles of H2O will you produce? • If you have 2 moles of O2, how many moles of H2O will you produce? • If you have 4 moles of O2, how many moles of H2O will you produce?

  5. How To Use The Mole: Balance the Equation to answer the questions! • __H2(g) + __O2(g) __H2O(l) • If you have 2 moles of H2, how many moles of H2O will you produce? • 2 moles • If you have 4 moles of H2, how many moles of H2O will you produce? • 4 • If you have 2 moles of O2, how many moles of H2O will you produce? • 4 • If you have 4 moles of O2, how many moles of H2O will you produce? • 8 2 1 2

  6. For the reaction: ___Ca(s) + ___O2(s) ___CaO(s) • If you have 2 moles of Ca(s), how many moles of CaO(s) will you produce? • If you have 4 moles of Ca(s), how many moles of CaO(s) will you produce? • If you have 2 moles of O2, how many moles of CaO(s) will you produce? • If you have 4 moles of O2, how many moles of CaO(s)will you produce?

  7. For the reaction: ___Ca(s) + ___O2(s) ___CaO(s) • If you have 2 moles of Ca(s), how many moles of CaO(s) will you produce? • 2 moles • If you have 4 moles of Ca(s), how many moles of CaO(s) will you produce? • 4 • If you have 2 moles of O2, how many moles of CaO(s) will you produce? • 4 • If you have 4 moles of O2, how many moles of CaO(s)will you produce? • 8 2 1 2

  8. For the reaction: __Mg(s) + __FeCl3(aq) __Fe(s) + __MgCl2(aq) • If you have 3 moles of Mg(s), how many moles of MgCl2(aq) will you produce? • If you have 3 moles of Mg(s), how many moles of Fe(s) will you produce? • If you have 2 moles of FeCl3(aq), how many moles of MgCl2(aq) will you produce? • If you have 4 moles of FeCl3(aq), how many moles of Fe(s) will you produce?

  9. For the reaction: __Mg(s) + __FeCl3(aq) __Fe(s) + __MgCl2(aq) • If you have 3 moles of Mg(s), how many moles of MgCl2(aq) will you produce? • 3 moles • If you have 3 moles of Mg(s), how many moles of Fe(s) will you produce? • 2 moles • If you have 2 moles of FeCl3(aq), how many moles of MgCl2(aq) will you produce? • 3 moles • If you have 4 moles of FeCl3(aq), how many moles of Fe(s) will you produce? • 4 moles 2 3 2 3

  10. Practice As a Group: • __C(s) + __H2(g) __CH4(g) • How many moles of CH4(g) are produced when you have: • 3 moles C(s)? • 4 moles C(s)? • __ Zn(s) + __ I2(s) __ ZnI2(s) • How many moles of ZnI2(s) are produced when you have: • 2 moles Zn(s)? • 3 moles I2(s)? • __ H2O2(aq) __ H2O(l) + __ O2(g) • How many moles of H2O(l) are produced when you have: • 2 moles H2O2(aq)? • 4 moles H2O2(aq)? • How many moles O2(g) are produced when you have: • 2 moles H2O2(aq)? • 4 moles H2O2(aq)?

  11. Practice As a Group: • __C(s) + __H2(g) __CH4(g) • How many moles of CH4(g) are produced when you have: • 3 moles C(s)? • 4 moles C(s)? • __ Zn(s) + __ I2(s) __ ZnI2(s) • How many moles of ZnI2(s) are produced when you have: • 2 moles Zn(s)? • 3 moles I2(s)? • __ H2O2(aq) __ H2O(l) + __ O2(g) • How many moles of H2O(l) are produced when you have: • 2 moles H2O2(aq)? • 4 moles H2O2(aq)? • How many moles O2(g) are produced when you have: • 2 moles H2O2(aq)? • 4 moles H2O2(aq)? 1 2 1 1 1 1 2 2 1

  12. Remember thatoxidation andreduction occurtogether…

  13. Rule 1 The oxidation # of an atom by itself is zero. Ex: Na – oxidation # of __. Ex: Cl2 – oxidation # of __. Ex: H2348 – oxidation # of __.

  14. Rule 1 The oxidation # of an atom by itself is zero. Ex: Na – oxidation # of 0. Ex: Cl2 – oxidation # of __. Ex: H2348 – oxidation # of __.

  15. Rule 1 The oxidation # of an atom by itself is zero. Ex: Na – oxidation # of 0. Ex: Cl2 – oxidation # of 0. Ex: H2348 – oxidation # of __.

  16. Rule 1 The oxidation # of an atom by itself is zero. Ex: Na – oxidation # of 0. Ex: Cl2 – oxidation # of 0. Ex: H2348 – oxidation # of 0.

  17. Rule 2 The oxidation # of any ion is the charge written. Ex: Na+ – oxidation # of __. Ex: Cl2- – oxidation # of __.

  18. Rule 2 The oxidation # of any ion is the charge written. Ex: Na+ – oxidation # of 1+. Ex: Cl2- – oxidation # of __.

  19. Rule 2 The oxidation # of any monatomic ion is the charge written. Ex: Na+ – oxidation # of 1+. Ex: Cl2- – oxidation # of 2-.

  20. Rule 3 The sum of the ox #s in a compound is zero. Ex: NaCl – Na+Cl- = 0

  21. Rule 3 The sum of the ox #s in a compound is zero. Ex: NaCl – Na+Cl- = 0 Ex: H2O – H2O-2 = 0. +

  22. Rule 4 The sum of the ox #s in a polyatomic ion is equal to the charge. Ex: (H2PO4)- – oxidation # of __.

  23. Rule 4 The sum of the ox #s in a polyatomic ion is equal to the charge. Ex: (H2PO4)- – oxidation # of 1-.

  24. Rule 5 Oxidation #s to remember: Elements in Group 1: always 1+ Elements in Group 2: always 2+ Aluminum: always 3+

  25. Rule 5 Oxidation #s to remember: • Fluorine: always 1- • Hydrogen: usually 1+ • Oxygen: usually 2-

  26. H3PO4

  27. Assign what you know first H3PO4

  28. Figure out missing ox# H3PO4 3+ 8-

  29. Figure out missing ox# H3PO4 3+ 5+ 8-

  30. Examples Na  Na+ (ox or red?) Cl2  2Cl- (ox or red?)

  31. Examples 0 1+ Na  Na+ (ox or red?) Cl2  2Cl- (ox or red?)

  32. Examples 0 1+ Na  Na+ (ox or red?) Up Cl2  2Cl- (ox or red?)

  33. Examples 0 1+ Na  Na+ (ox or red?) Up Lost e- Cl2  2Cl- (ox or red?)

  34. Examples 0 1+ Na  Na+ (ox or red?) Up Lost e- Oxidation Cl2  2Cl- (ox or red?)

  35. Examples Na  Na+ (ox or red?) Cl2  2Cl- (ox or red?) 0 1-

  36. Examples Na  Na+ (ox or red?) Cl2  2Cl- (ox or red?) Down 0 1-

  37. Examples Na  Na+ (ox or red?) Cl2  2Cl- (ox or red?) Down Gain e- 0 1-

  38. Examples Na  Na+ (ox or red?) Cl2  2Cl- (ox or red?) Down Gain e- Reduction 0 1-

  39. Examples Fe  Fe2+ (ox or red?) Cu2+  Cu (ox or red?)

  40. Examples What are the oxidation #’s: S in (H2SO4)- S in (SO3)2-

  41. Concentration of Reactants/Products • Remember: concentration is the amount of stuff in a space • If you add more reactants, the reaction will go [forward or backward] faster • The reaction will go forward faster • Equilibrium will shift to the right • 2NaCl + CaCO3 Na2CO3 + CaCl2 • Paper clipping

  42. Practice Problems • 2SO2(g) + O2(g) + heat  2SO3

  43. Temperature • Exothermic: heat_______ • Endo thermic: heat _______ • 2NaCl + CaCO3 Na2CO3 + CaCl2 + heat • 2SO2(g) + O2(g) + heat  2SO3 • Endothermic: heat is a reactant • Exothermic: heat is a product

  44. Temperature • If you add heat to an exothermic reaction, the equilibrium will shift left • And vice-versa: If you add heat to an endothermic reaction, the equilibrium will shift right • 2NaCl + CaCO3 Na2CO3 + CaCl2 + heat • 2SO2(g) + O2(g) + heat  2SO3

  45. Practice C (g) + O2 (g)  CO2 (g)+ heat Which direction would the reaction shift if I… • Increased the concentration of O2? • Increased the concentration of CO2? • Increased the concentration of O2? • Added heat? • Made it colder? • Put it on a hot plate?

  46. Ways of changing Equilibrium • Concentration • Done • Temperature • Done • Volume • Up next • Pressure • Right after

  47. Volume! • Only affects gases! • Gases expand to fill space given • Increase volume, reaction shifts to side with more moles of gas • Decrease volume, reaction shifts to side with fewer moles of gas • First Step! Count moles of gas- ignore rest! • To count, add coefficients of gas

  48. How many molecules? • C (g) + O2 (g)  CO2 (g)+ heat • 2SO2(g) + O2(g)  2SO3 (g) + heat • CO(g) + H2O (g) + heat  CO2(g) + H2(g) • Ca(s) + H2O (g) + heat  CaO(s) + H2(g)

  49. Volume Example • C + O2 (g) <-> 2CO (g) • C + O2 (g) <-> CO2 (g) • LiF + NaOH <-> LiOH + NaF

  50. More Practice • 2SO2(g) + O2(g)  2SO3 (g) + heat • CO(g) + H2O (g) + heat  CO2(g) + H2(g) • Ca(s) + H2O (g) + heat  CaO(s) + H2(g)

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