Presentation on theme: "Finish up redox Demo voltaic cell, then how does a re-charging battery work? Celebrate redox with nuclear chem soon enough Draw the standard 2 beaker voltaic."— Presentation transcript:
Finish up redox Demo voltaic cell, then how does a re-charging battery work? Celebrate redox with nuclear chem soon enough Draw the standard 2 beaker voltaic cell, with Iron in Fe(NO 3 ) 3(AQ) and then Copper with CuCl 2(AQ) solution. Use KCl (AQ) for the salt bridge
Look at the demo of this electrochemical cell. What 3 things run out when this battery dies? What is the difference between this voltaic cell and an electrolytic chemical cell? Do they both use Redox reactions? Then explain that? What is the difference between spontaneous and non-spontaneous?
How does a recharging car battery work? (All recharging batteries are the same, although they all use different anodes, cathodes, and different solutions). The redox forward and reverse is the same idea. The reactions are as follows: When the battery is fully charged the lead metal is in sulfuric acid. The oxidation reaction produces the electricity to start your car. A lot of electricity is produced quickly. The battery runs down quickly. Once the car engine is running (burning gas), the alternator reverses course, and the car engine produces electricity which is forced back into the battery, forcing the reverse redox reactions to happen. When this happens, the battery is recharged, ready to be used again, once the car is off. Cars do not use much electricity when running, if they do, its produced by the engine. The battery can be recharged over and over. Only when problems arise, reactions become incomplete, leaks of acid, cracks, etc. occur, will break a battery down. In theory it should recharge forever. Usually car batteries can last for many years, which is pretty good I think.
DISCHARGING Pb + PbO 2 + 2H 2 SO 4 2PbSO 4 + 2H 2 O RECHARGING In the morning, my battery is on the left. I turn the key, and connect the wires, and the battery makes electricity this way (only the lead changes around): Pb° + Pb +4 O 2 + 2H 2 SO 4 2Pb +2 SO 4 + 2H 2 O oxidation reduction Lead atoms become oxidized and release electrons to start my car. The Pb +4 cations pick up these electrons and get reduced at the same time.
Once my car is running, the reverse reactions occur, because my engine pumps electricity into the battery. That forces a redox that is not spontaneous but recharges the batteries. Pb° + Pb +4 O 2 + 2H 2 SO 4 2Pb +2 SO 4 + 2H 2 O Recharging means the Pb +2 cations oxidize (lose electrons) and form the Pb +4 cations. The reduction here (gaining electrons) has the Pb+2 cations reduce into Pb ° atoms. reduction oxidation
The half reactions for discharging (starting the car) are: ½ OX: Pb° Pb e -1 ½ RED: Pb e -1 Pb +2 The half reactions for re-charging the battery are: ½ OX: Pb +2 Pb e -1 ½ RED: Pb e -1 Pb°