voltaic cell
Technically, any redox reaction can be set up to make a voltaic cell. In modern society, however, only certain redox reactions are put to practical use. A portable voltaic cell that generates electricity to power devices for our convenience is called a battery. All batteries are based on redox reactions. The first battery called a voltaic pile was constructed by the Italian scientist Alessandro Volta in 1800 and was based on the copper/zinc reaction depicted in - ball-ch14_s03_f01. Unfortunately, it was messy, requiring quantities of copper and zinc salts dissolved in water. In 1866, the French scientist Georges Leclanché invented the dry cell, a precursor to todays modern battery. A schematic of a dry cell is shown in - ball-ch14_s03_f02. The zinc case and the central carbon rod serve as the anode and cathode, respectively. The other reactants are combined into a moist paste that minimizes free liquid, so the battery is less messy hence the name dry cell . The actual redox reaction is complex but can be represented by the following redox reaction: + 2+ Zn + 2MnO2 + 2NH4 Zn + Mn2O3 + 2NH3 + H2O A dry cell has a voltage of about 1.56 V. While common and useful, dry cells have relatively short lifetimes and contain acidic components. They also cannot be recharged, so they are one-use only. Batteries that can be used only once are calledprimary batteries. Figure 14.2 Dry Cells.