Oxidation Numbers & Redox Reactions. How to Make Balancing Redox Reactions a Relatively Painless Process. What Do We Need to Consider?. Definitions Rules for Assigning Oxidation Numbers Balancing Redox Reactions. What are Oxidation Numbers?.
How to Make Balancing Redox Reactions a Relatively Painless Process
This cell produces 1.10 volts
The cell works because the valence electrons of zinc have a higher energy than the valence electrons of copper. This gives zinc a greater tendency to give up electrons than copper. In the external circuit, electrons will always move from the positive anode to the negative cathode.
A shorthand for representing the half-cell reaction is:
This cell operates because: Copper metal takes electrons away from zinc metal. These electrons move from the anode to the cathode through the external circuit. The newly formed Zn+2 go into solution. SO4-2 ions in solution move from the cathode to the anode through the salt bridge. The cell continues to operate as long as there is a potential energy difference between the half-cells. The shorthand for the zinc-copper cell is:Zn|Zn+2||Cu+2|Cu The anode (oxidation reaction) is always on your left. The cathode (reduction reaction) is always on your right. The two vertical lines between the half-cells represent the "salt bridge".
Dry cell - acid form
This is the source of power for an ordinary flashlight. Most "flashlight batteries" produce 1.5 volts. The case of the cell is zinc metal acting as the anode. At the center of the cell is a stick of graphite for the cathode. The graphite stick is surrounded by a paste of MnO2 and NH4Cl.
Anode - Zn (s) Zn+2 + 2e -
Cathode - 2NH4+ (aq) + 2MnO2 (s) + 2e - Mn2O3 (s) + 2NH3 (aq) + H2O (l)
Remember that the term "battery" refers to two or more cells connected together. The 9-volt transistor battery is a true battery. It contains six individual 1.5 volt cells connected in series to produce 9 volts.
The NH4Cl in the "acid form" cell is replaced by KOH and the zinc is in powder form rather than a solid piece of metal. The graphite cathode is eliminated and acid corrosion of the container does not occur. The alkaline cell is more efficient and can be miniaturized to fit more varied applications.
Your level of understanding of this material will determine your success with the electrochemistry concept. Study the information until you are comfortable with it. Write the answer for the following questions:
Fuel Cell Electrode DiagramThis picture contains active zones.Click and explore!
A diagram of one electrode pair is shown opposite. Hydrogen and oxygen are supplied to the cell as molecular gases which are dissociated by catalyst material on the electrodes. At the Anode (negative electrode) hydrogen gas is dissociated into two protons (H+) and twoelectrons (e_). The protons can travel throughthe polymeric proton exchange membrane:PEM (a solid electrolyte) and combine with oxygen ions generated at the Cathode (positive electrode) to form water.
TheFuel Cell Apparatus These pictures contains active zones. Click and explore!