Leclanche dry cells

The Leclanche dry cell with zinc replaced by magnesium offers considerable advantages. In the electromotive series, magnesium occupies a more basic position as compared to zinc ( n = -0.76 V / g = -2.38 V), and this means that the voltage of a magnesium cell is greater than that of a similar zinc cell. 

FIGURE 17.6 In a Leclanche dry cell, electrons are released to an external circuit at the anode and enter the cell again at the cathode, where the reduction of Mn02 occurs. 

Alkaline dry cells are similar to Leclanche dry cells except that (1) the electrolyte is basic (alkaline) because it contains KOH, and (2) the interior surface of the Zn container is rough this gives a larger surface area. Alkaline cells have a longer shelf life than ordinary dry cells, and they stand up better under heavy use. The voltage of an alkaline cell is about 1.5 volts. During discharge, the alkaline dry cell reactions are... 

The nickel-cadmium (nicad) cell has gained widespread popularity because it can be recharged. It thus has a much longer useful life than ordinary (Leclanche) dry cells. Nicad batteries are used in electronic wristwatches, calculators, and photographic equipment. 

Sketch and describe the operation of (a) the Leclanche dry cell, (b) the lead storage battery, and (c) the hydrogen-oxygen fuel cell. 

The inexpensive flashlight batteries sold in retail stores use a design called a Leclanche dry cell, diagrammed in Figure 14-4. The body of the battery is made of zinc, which acts as the anode. The zinc is oxidized according to the following reaction ... 

Use chemical equations to describe a Leclanche dry cell or inexpensive battery. How do alkaline batteries differ ... 

We commonly use voltaic cells as convenient, portable sources of energy. Flashlights and radios are examples of devices that are often powered by the zinc-carbon, or Leclanche, dry cell (Figure 20.9). This voltaic cell has a zinc can as the anode a graphite rod in the center, surrounded by a paste of manganese dioxide, ammonium and zinc chlorides, and carbon black, is the cathode. The electrode reactions are complicated but are approximately these ... 

Nernst equation (20.7) zinc-carbon (Leclanche) dry cell (20.8) alkaline dry cell (20.8) lithium-iodine battery (20.8) lead storage cell (20.8) nickel-cadmium cell (20.8)... 

Describe the zinc—carbon, or Leclanche, dry cell and the lead storage battery. 

Alkaline dry cell a voltaic cell that is similar to the Leclanche dry cell but uses potassium hydroxide in place of ammonium chloride. (20.8)... 

Table 54.1 Union Carbide carbon-zinc Eveready Leclanche dry cells and batteries...

Table 54.2 Estimated average service life at 21 °C for a selection of Union Carbide Eveready carbon- zinc Leclanche dry cells and batteries, voltage range 1.5-9V... 

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