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The Breathalyzer

The Breathalyzer. The Breathalyzer. The Breathalyzer Reaction C 2 H 5 OH + Cr 2 O 7 2- + H + → CH 3 COOH + Cr 3+ + H 2 O Ethanol Orange Acid Acetic Acid Green Water If the orange colour decreases there is alcohol present.

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The Breathalyzer

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  1. The Breathalyzer

  2. The Breathalyzer

  3. The Breathalyzer Reaction C2H5OH + Cr2O72- + H+ → CH3COOH + Cr3+ + H2O EthanolOrange AcidAcetic AcidGreen Water If the orangecolour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mL Legal Limit New Driver0.00 mg/mL

  4. Test tubes each contain 5 mL 0.25 M K2Cr2O7 + 5 mL of 6.0 M H2SO4 + 1 drop of 0.10 M AgNO3 (catalyst) and 0, 1, 2, 3, 4, drops respectively of 10.0 % ethanol. 0.20 % 0.15 % 0.10 % 0.000 % 0.05 %

  5. Redox Titrations A redox titrationis the same as an acid-base titration except it involves a redox reaction. Reagents are chosen so that the reaction is spontaneous. Pick a suitable reagent for redox titration involving IO3- in acid solution. A F- B I- C SO42- D Cl-

  6. Pick the spontaneous reaction

  7. 6.75 mL of 0.100 M KMnO4 is required to titrate 25.0 mL of FeCl2. Calculate the [Fe2+]. MnO4- + 8H+ + 5Fe2+ → Mn2+ + 4H2O + 5Fe3+ 0.00675 L 0.0250L 0.100 M ? M x 0.100 mole 1 L x 5 moles Fe2+ 1 mole MnO4- 0.00675 L MnO4- [Fe2+] = 0.0250 L = 0.135 M

  8. Write the anode and cathode reactions. voltmeter NaNO3aq) Pt Pt Inert electrodes- look at the solution for the reactions MnO4- in acid H2O2(aq)

  9. Cathode Anode

  10. Cathode: MnO4- + 8H+ + 5e-→ Mn2+ + 4H2O Anode: H2O2→ O2 + 2H+ + 2e- What happens to the mass of the cathode? Constant What happens to the mass of the anode? Constant What happens to the pH of the cathode? Increases What happens to the pH of the anode? Decreases

  11. Non-Inert Electrodes The Cathode will stay inert A non-inertAnodemight oxidize DC Power - + Cu might oxidize - Cathode Reduction 2H2O + 2e-→H2 +2OH- -0.41 v Cu Cu K+ SO42- H2O K2SO4(aq)

  12. You must look at the possible oxidation of: SO42- H2O Cu Strongest Reducing Agent

  13. Non-Inert Electrodes The Cathode will stay inert A non-inertAnodemight oxidize DC Power - + Cu might oxidize Cu Cu K+ SO42- H2O - Cathode Reduction 2H2O + 2e-→H2 +2OH- -0.41 v + Anode Oxidation Cu(s)→ Cu2+ + 2e- -0.34 v K2SO4(aq)

  14. Review of Cells ElectrochemicalElectrolytic Is a power supplyRequires power supply Spontaneous (+)Nonspontaneous (-) Makes electricityMakes chemicals Reduction is highest on Chart Reduction is the –ve

  15. For all cells: Cations migrate to the cathode, which is the site of reduction. Anions migrate to the anode, which is the site of oxidation. Electrons travel through the wire from anode to cathode.

  16. Complete the Chart Electrochemical Cell: Zn, Zn(NO3)2 II Cu, CuSO4 Anode:Reaction: Cathode:Reaction: E0 = Zn Zn(s) → Zn2+ + 2e- 0.76 v 0.34 v Cu Cu2+ + 2e- → Cu(s) 1.10 v Higher on reduction Chart

  17. Electrolytic Cell: Molten AlCl3 Anode: Reaction: Cathode: Reaction: Al3+ Cl- C 2Cl- → Cl2(g) + 2e- -1.36 v Al3+ + 3e- → Al(s) -1.66 v C MTV = +3.02 v E0 = -3.02 v The anode and cathode are inert C or Pt Vowels: Anode Anion Oxidation Consonants: Cathode Cation Reduction

  18. Electrolytic Cell: KBr(aq) K+ Br- H2O Anode: Cathode: C C Anode Oxidation Anion or Water

  19. Oxidation of water

  20. Electrolytic Cell: KBr(aq) K+ Br- H2O Anode: 2Br- → Br2(g) + 2e--1.09 v Cathode: C C Anode Oxidation Anion or Water Cathode Reduction Cation or water

  21. Electrolytic Cell: KBr(aq) K+ Br- H2O Anode: 2Br- → Br2(g) + 2e--1.09 v Cathode: 2H2O+ 2e- → H2(g) + 2OH--0.41 v C C MTV = +1.50 v E0 = -1.50 v Anode Oxidation Anion or Water Cathode Reduction Cation or water

  22. Is Al a reactive or non-reactive metal? Look on page 8 Reactiveas Al is a relatively strong reducing agent. Why is Al used for boats, patio furniture, swing sets, and trucks boxes? Al makes a clear transparent Al2O3 paint like coating that prevents further oxidation.

  23. How to Fail a Breathalyzer Video 1 Breathalyzer Video 2 Drunks Jeff Dunham

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