4541 CHEMISTRY Chapter 6 C Analysing Voltaic Cell // Chemical Cell A chemical cell that produces electrical energy when chemical reactions occur in it. (I) Simple cell 1. Produced when two different metals are immersed in an electrolyte and are connected by an external circuit. 2. The voltage of chemical cell depends on the distance between the two metals in the Electrochemical Series : the further the distancebetween them, the higher is the voltage. Example : Simple cell using magnesium and copper strips as electrodes and copper(II) sulphate solution as electrolyte. Chapter 6 Electrochemistry 31 Position of magnesium is higher than copper in the Electrochemistry Series. A magnesium atom release electrons more easily than a copper atom. Mg → Mg 2 + + 2e The Mg 2 + ions are released into the CuSO 4 solution while the electrons that are released flow through the external circuit toward the copper plate. At the copper electrode, the electrons are accepted by the Cu 2 + ions. Cu 2 + + 2e → Cu The copper atoms are formed. Brown solid is deposited at cathode. Cathode becomes thicker. The size of the cathode becomes bigger. The mass of the cathode increases. Magnesium CopperCopper(II) sulphate solution Electron flow Electron flow Electrical current produced is detected by the voltmeter/galvanometer[Chemicalenergy →Electricalenergy] Positive terminal : Less electropositive metal. The electrons that flow from the external circuit are received by the positive ion in the electrolyte through this terminal. Metallic ion becomes metal atom(becomes thicker). Negative terminal : More electropositive metal. Metal atom will release electrons that will flow through the external circuit. Metal atom becomes metallic ion (becomes thinner). v + -
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