Electrochemical Cells - Chemistry - Class12 Physics Wallah Notes

1. Electrochemical Cells - Chemistry - Class12 Physics Wallah Notes Electrochemistry of Class 12 Electrochemical cells are cells in which chemical energy is converted into electrical energy. This means that chemical reactions produce an electric current. Chemical energy is transformed into electrical energy in electrochemical cells. This implies that electrical current is created by chemical reactions. Two electrodes (metallic conductors) in contact with an electrolyte and an ionic conductor make up an electrochemical cell (which may be a solution, a liquid, or a solid). An electrode and its electrolyte compose an electrode compartment. The electrolyte between the two electrodes can be the same. The many varieties of electrodes are summarised in the following table and represented in the accompanying graphic. Can also view the Chemical Properties of Acid class 10

2. Different Types Of Electrodes S. No. Electrode type Designation Half-reaction (a) Metal−metal ion M+(aq) | M(s) M+(aq)+e− → M(s) X+(aq) | X2(g)⏐ Pt(s) (b) Gas−ion electrode X+(aq)+e− → ½X2(g) X−(aq ) ⏐X2(g ) | Pt(s) ½X2(g)+e− → X−(aq) X−(aq) | MX(s)⏐M(s) (c) Metal−insoluble salt−anion MX(s)+e−→M(s)+X−(a q) (d) Redox electrode M2+ (aq) ,M+(aq) | Pt(s) M2+ (aq)+e− → M+ (aq) (a) (b)

3. (c) (d) In a given electrochemical cell, a combination of any of the two electrodes can be used. The cell may even contain the same types of electrodes with different concentrations of electrolytes. For example, Pt(s) | X2 ( 1 atm) | X+ (c1 M) || X+ (c2 M) | X2 ( 1 atm) | Pt(s) When an ‘inert metal’ is part of the cell, it is present to act as a source of electrons, but takes no other part in the reaction other than acting as a catalyst for it. If the electrolytes are different, the two compartments may be joined by a salt bridge, which is a concentrated electrolyte solution in agar−agar jelly that completes the electrical circuit and enables the cell to function. A galvanic cell is an electrochemical cell that produces electricity as a result of the spontaneous reaction occurring inside it. One of the simplest electrochemical cells, called the Daniel cell is shown in the given figure. It consists of two redox couples such as Cu2+ | Cu at one end and Zn2+ | Zn at the other end. Since Zn has a higher oxidation potential than Cu, it gets oxidized to Zn2+at anode. At the same time, Cu2+ gets reduced to Cu at the cathode. The salt bridge contains a highly soluble electrolyte (like KCl, NH4NO3, NH4Cl, KNO3, etc) in which ionic mobilities of cation and anion are of comparable order. The zinc rod which has the electron left by the zinc (that got oxidized) becomes negatively charged

4. while the Cu rod which lost the electrons to Cu2+ becomes positively charged. As these two half cells are connected through connecting wires and an ammeter, electric current flows which is indicated by a deflection in the ammeter showing that a chemical reaction is occurring in the cell. During the course of the reaction, the zinc rod gets dissolved and copper is deposited on the copper rod. Thus the concentration of the anode solution increases while that of the cathode solution decreases. The flow of electrons occurs from the zinc rod to the copper rod in the external circuit. The current flow is continuous as long as the electrical connections and the salt bridge are maintained and a sufficient amount of reactant solution remains. Original source: https://www.pw.live/chapter-electrochemistry/electrochemical-cells