Reactions in electrochemical cells

The electron transfer processes that occur In respiration and photosynthesis can 

In an electrochemical cell, the electronic conductor and its surrounding electrolyte is an electrode. The physical structure contcuning them is called an electrode compartment. The two electrodes may shcue the Scune compartment (Fig. 5.3). If the electrolytes are different, then the two compcutments may be joined by a salt bridge, which is an electrolyte solution that completes the electrical circuit by permitting ions to move between the compartments (Fig. 5.4). Alternatively, the two solutions may be in direct physical contact (for example, through a porous membrane) and form a liquid junction. However, a liquid junction introduces complications to the interpretation of measurements, cuid we shall not consider it further. 

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In some cases, as in reactions in electrochemical cells or other reactions involving oxidation-reduction, the half reactions of the ions are useful. Consider the Daniell cell, which consists of a zinc electrode in a zinc sulfate solution, and a copper electrode in a copper solution, the two solutions being separated by a porous partition. The half reactions are... 

Why is it that half-reactions in electrochemical cells proceed spontaneously in one direction and furnish current ... 

Faraday (1791-1867) was bom in England, a child of a poor blacksmith. At the age of 14 he was apprenticed to a bookbinder who gave him time to read and to attend lectures. In 1812 he became an assistant in Humphry Davy s laboratory at the Royal Institution. He succeeded Davy as the most famous and influential scientist in England, making an amazing number of important discoveries, including his formulation of the quantitative relationships between electrical current and the extent of chemical reaction in electrochemical cells. 

Electrochemical reactions in electrochemical cells can be described in terms of electrical variables (electrode potential, electrical current or... 

Earlier techniques are used to help students learn to balance chemical reactions in electrochemical cells. Knowledge of oxidation and reduction processes from earlier chapters helps students gain a better ability to recognize these processes in electrochemical cells. 

There are two types of electrochemical cells. A galvanic or voltaic cell produces electric current from a spontaneous reaction, whereas an electrolytic cell has an external current source, such as a battery, to drive a nonspontaneous reaction. Reactions in electrochemical cells are redox reactions since they involve a transfer of electrons from a reducing agent to an oxidizing agent. The reduction reaction withdraws electrons from one electrode, the positive electrode or cathode. The oxidation reaction supplies electrons to the other electrode, the negative electrode or anode. Current flows via an external circuit from the anode to the cathode. 

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