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What is powering this clock ?

What is powering this clock ?. How much Voltage. You can see the battery is missing and the clips are attached to the terminals. What is the voltage required to run the clock?. Make a Battery.

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What is powering this clock ?

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  1. What is powering this clock?

  2. How much Voltage • You can see the battery is missing and the clips are attached to the terminals. • What is the voltage required to run the clock?

  3. Make a Battery Place a drop of Copper nitrate on one end of the paper. Place a piece of copper in the center of the wet spot

  4. Make a Battery On the other end place a drop of zinc nitrate and place a piece of zinc in the wet solution.

  5. Make a Battery Add a couple of drops of KNO3 in the middle of the two solutions to make a salt bridge.

  6. Make a Battery Touch the probe leads to the two metals as pictured here. Record the voltage. V

  7. What’s the sign? • If the reading is negative, switch the leads to the other metals. You want to get a positive voltage reading. • Record the metal that is at the red lead and the metal at the black lead.

  8. REDUCE RED CATS • This is the way I remember that reduction occurs at the cathode and it is at the red lead. • Reduction ? • Oxidation ?

  9. Look at the Standard Reduction Potential Table • Cu2+ • Cu • Zn2+ • Zn

  10. Find the voltage for each pair of metals you have. ?

  11. 1.1 volts Cu Zn Cu(NO3)2 Zn(NO3)2 • Cu2+ + 2 e- Cu 0.34 volts • Zn  Zn2+ + 2e- 0.76 volts • 1.10 volts

  12. 1.1 volts Cu Zn Cu(NO3)2 Zn(NO3)2 What is the purpose of the salt bridge?

  13. What is powering this clock?

  14. How much Voltage • You can see the battery is missing and the clips are attached to the terminals. • What is the voltage required to run the clock?

  15. After adding the phenolphthalein around the strip of magnesium a pink color is observed. • Also there are tiny bubbles all along the sides of the magnesium

  16. Lead Battery Anode:Pb(s) + HSO4-PbSO4(s) +H+(aq) 2 e- cathode: PbO2(s) + 3 H+ +HSO4 + 2e- PbSO4 + H2O 0.296 V 1.628 V 1.924 V

  17. Mercury Battery STEEL cathode HgO in KOH Zn(OH)2 Zn container anode Watches, pacemakers, calculators

  18. Rechargeable Nickel-cadmium anodeCd + OH- Cd(OH)2 + 2 e- cathodeNiO(OH)S + H2O Ni(OH)2 + OH- Recharge many times because the solid products adhere to the surface of the electrode renewing the battery.

  19. Corrosion • Corrosion is the oxidative deterioration of a metal such at rust. O2 from the air Drop of water O2 + 4H+ + 4 e-  2 H2O cathode Fe --> Fe2+ + 2 e-anode Rust

  20. How can you prevent corrosion? • Look at the equation and prevent the reaction from happening. What can you do?

  21. Electrochemical Cells • There are 2 types of cells • Galvanic also called voltaic is a spontaneous reaction that produces an electric current - Electrolytic requires an outside source to supply the current such as a battery or electrical outlet

  22. Electroplating • Example of an Electrolytic cell • Silverplated dinnerware - Silver is a soft metal what would happen if you used a solid silver fork?

  23. Battery Electrolysis Electrolysis Black lead cathode - Red lead + anode Graphite electrodes Na2SO4(aq)

  24. What is happening?? • Reduction: 2 H2O(l) + 2 - H2(g) + 2 H-(aq) -0.83 V 2 H+(aq) 3 e- H2(g) 0.00 V Na+(aq)+ e- Na(s) -2.71 V • Oxidation: 2 H2O  O2(g) + 4H+(aq) + 4e- -1.23 V 2 SO42-  S2O8 + 2 e- -2.00 V

  25. See bubbles? What is the clue? • Look at the data table again and see which reactions you think took place

  26. What is happening?? • Reduction: 2 H2O(l) + 2 - H2(g) + 2 H-(aq) -0.83 V 2 H+(aq) 3 e- H2(g) 0.00 V Na+(aq)+ e- Na(s) -2.71 V • Oxidation: 2 H2O  O2(g) + 4H+(aq) + 4e- -1.23 V 2 SO42-  S2O8 + 2 e- -2.00 V

  27. Answer • Reduction was water or Na+ • We know is must be water for 3 reasons - • 1. a gas was produced • 2. sodium reacts with water violently • 3. It became more basic 2H2O + 2 e- --> H2(g) + 2 OH- -.83V

  28. Oxidation was either water of sulfate ion Oxidation of water produces H+ and a gas. Do we have evidence of that? H2O --> O2(g) + 4 H+ + 4 e- -1.23 V

  29. Energy Involved 2H2O + 2 e- --> H2(g) + 2 OH- -.83V H2O --> O2(g) + 4 H+ + 4 e- -1.23 V - 2.06 V What does the negative sign mean?

  30. Battery Change the electrodes to Copper Black lead cathode - Red lead + anode Copper electrodes Na2SO4(aq)

  31. What is happening?? • Reduction: 2 H2O(l) + 2 - H2(g) + 2 H-(aq) -0.83 V 2 H+(aq) 3 e- H2(g) 0.00 V Na+(aq)+ e- Na(s) -2.71 V Cu2+ + 2 e-- Cu - 0.34 V Oxidation: 2 H2O  O2(g) + 4H+(aq) + 4e- -1.23 V 2 SO42-  S2O8 + 2 e- -2.00 V Cu(s)- Cu2+ + 2 e- +0.34 V

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