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Redox Reactions. Mindy Goho Tyler Walther. Oxidation vs Reduction. An important concept of redox reactions is the movement of electons If a molecule loses electrons it is OXIDIZING If a molecule gains electrons it is REDUCING. An Easy Way to Remember. LEO the lions says GER.
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Redox Reactions Mindy Goho Tyler Walther
Oxidation vs Reduction • An important concept of redox reactions is the movement of electons • If a molecule loses electrons it is OXIDIZING • If a molecule gains electrons it is REDUCING
An Easy Way to Remember LEO the lions says GER Loss of Electrons = Oxidation Gain of Electrons = Reduction
Agents • Oxidizing agents gain electrons. • Reducing agents lose electrons. OxidizingAgent 2 Mg+O2->2 MgO Reducing Agent
How to Solve a Redox Equation Steps: 1. Use oxidation numbers to decide what is oxidizing and what is reducing. (Review how to find oxidation numbers if necessary) 2. Separate the equation into half reactions. 3. Balance all non-H’s and O’s 4. Balance all oxygens with water (H2O) 5. Balance all H’s with hydrogens 6. Balance charges with electrons. 7. Make the electrons of both half reactions match. 8. Recombine the half reactions
0 +1 +5 -2 +6 -2 +1 -2 +2 -2 Sn + HNO3 SnO2 + H2 O + NO Step 1: Use oxidation numbers to decide what is reducing and oxidizing Sn is oxidizing and N is reducing Step 2: Write half reactions Oxidizing: Sn SnO2 Reducing: HNO3 NO Step 3: No non- H’s and O’s to balance
0 +1 +5 -2 +6 -2 +1 -2 +2 -2 • Sn + HNO3 SnO2 + H2 O + NO Step 4: Balance all oxygens with water Reducing: HNO3 NO + 2H2O Oxidizing: 2 H2O + Sn SnO2 Step 5: Balance all H’s with Hydrogen Oxidizing: 2 H2 O + Sn SnO2 + 4H+1 Reducing: 3H+1+ HNO3 NO + 2H2O Step 6: Balance all charges with electrons Reducing: 3e- + 3H+1+ HNO3 NO + 2H2O Oxidizing: 2 H2 O + Sn SnO2 + 4H+1+ 4e-
0 +1 +5 -2 +6 -2 +1 -2 +2 -2 • Sn + HNO3 SnO2 + H2 O + NO Step 7: Make the elecrtons of both half reactions match Oxidizing: (2 H2 O + Sn SnO2 + 4H+1+ 4e-) 3 Reducing: (3e-+ 3H+1+ HNO3 NO + 2H2O)4 Oxidizing: 6H2 O + 3Sn 3SnO2 + 12H+1+ 12e- Reducing: 12e-+ 12H+1+ 4HNO34NO+ 8H2O Step 8: Recombine half reactions (Remember that if you add something back in to one side you must add it to the other) 3Sn + 4HNO3 3SnO2 + 4NO + H2O
Quiz What is oxidizing? H Click screen to reveal answers! Mg What is reducing? HCl What is the reducing agent? What is the oxidizing agent? MgCl2
Quiz Identify the oxidizing/reducing agents. Click screen for answers. Reducing Agent Oxidizing Agent 2 Na + Cl2-> 2 NaCl Na Cl2 4 Li + O2-> 2 Li2O Li O2 2 K + 2 NH3-> 2 K+ + 2 NH2- + H2 K NH3 Click Screen to reveal answers!
Final Question! Balance this redox equation! Click the screen to reveal the answer to each step, after you try it on a sheet of paper! +1 -1 +1 +6 -2 0 +1 -2 +1 -2 HI + H2SO4 I 2 + H2S + H2O Step 1: Use oxidation number to determine what is oxidizing/reducing I is oxidizing and S is reducing Step 2: Write half reactions Oxidizing: HI I 2 Reducing: H2SO4 H2S
+1 -1 +1 +6 -2 0 +1 -2 +1 -2 HI + H2SO4 I 2 + H2S + H2O Step 3: Balance all non-H’s and O’s Oxidizing: 2HI I 2 Reducing: H2SO4 H2S Step 4: Balance all oxygens with water Oxidizing: 2HI I 2 Reducing: H2SO4 H2S + 4 H2O Step 5: Balance all H’s with Hydrogen Oxidizing: 2HI I 2 + 2H+ Reducing: 8H++ H2SO4 H2S + 4 H2O
+1 -1 +1 +6 -2 0 +1 -2 +1 -2 HI + H2SO4 I 2 + H2S + H2O Step 6: Balance all charges with electrons Oxidizing: 2HI I 2 + 2H+ +2e- Reducing: 8e-+8H+ + H2SO4 H2S + 4 H2O Step 7: Make the electrons of both half reactions match Oxidizing: (2HI I 2 + 2H+ +2e- ) 4 Reducing: 8e- +8H+ + H2SO4 H2S + 4 H2O Oxidizing: 8HI 4I2 + 8H+ +8e- Reducing: 8e- +8H+ + H2SO4 H2S + 4 H2O
+1 -1 +1 +6 -2 0 +1 -2 +1 -2 HI + H2SO4 I 2 + H2S + H2O Step 8: Recombine both half reactions Oxidizing: 8HI 4I 2 + 8H+ +8e- Reducing: 8e- +8H+ + H2SO4 H2S + 4 H2O 8HI + H2SO4 4 I 2 + H2S + 4H2O
You have successfully completed a redox equation! (And this tutorial!)