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    Radhika Sarawagi
    Electrochemical cells can convert either chemical energy to electrical energy (voltaic cell) or electrical energy to chemical energy (electrolytic cell). There are two main types: voltaic cells, where oxidation occurs at the anode and reduction at the cathode spontaneously, and electrolytic cells, where a non-spontaneous reaction is driven by an external voltage source. Voltaic cells contain two half-cells with different electrode materials separated by a salt bridge, allowing ion flow but not electron flow. Common voltaic cell electrodes include metal/metal ion combinations like zinc/zinc ion, with the more reactive metal oxidizing. Electrolytic cells contain an electrolyte, two electrodes, and a battery

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    9 2

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    Radhika Sarawagi
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    Electrochemical cells can convert either chemical energy to electrical energy (voltaic cell) or electrical energy to chemical energy (electrolytic cell). There are two main types: voltaic cells, where oxidation occurs at the anode and reduction at the cathode spontaneously, and electrolytic cells, where a non-spontaneous reaction is driven by an external voltage source. Voltaic cells contain two half-cells with different electrode materials separated by a salt bridge, allowing ion flow but not electron flow. Common voltaic cell electrodes include metal/metal ion combinations like zinc/zinc ion, with the more reactive metal oxidizing. Electrolytic cells contain an electrolyte, two electrodes, and a battery

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    Chem 9.2 notes ib

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    9.2

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    Electrochemical cells can convert either chemical energy to electrical energy (voltaic cell) or electrical energy to chemical energy (electrolytic cell). There are two main types: voltaic cells, where oxidation occurs at the anode and reduction at the cathode spontaneously, and electrolytic cells, where a non-spontaneous reaction is driven by an external voltage source. Voltaic cells contain two half-cells with different electrode materials separated by a salt bridge, allowing ion flow but not electron flow. Common voltaic cell electrodes include metal/metal ion combinations like zinc/zinc ion, with the more reactive metal oxidizing. Electrolytic cells contain an electrolyte, two electrodes, and a battery

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    40 views4 pages

    9 2

    Uploaded by

    Radhika Sarawagi
    Electrochemical cells can convert either chemical energy to electrical energy (voltaic cell) or electrical energy to chemical energy (electrolytic cell). There are two main types: voltaic cells, where oxidation occurs at the anode and reduction at the cathode spontaneously, and electrolytic cells, where a non-spontaneous reaction is driven by an external voltage source. Voltaic cells contain two half-cells with different electrode materials separated by a salt bridge, allowing ion flow but not electron flow. Common voltaic cell electrodes include metal/metal ion combinations like zinc/zinc ion, with the more reactive metal oxidizing. Electrolytic cells contain an electrolyte, two electrodes, and a battery

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    of 4

    ​9.

    2 Electrochemical cells 
    Electrochemical Cells 
    ● In an electrochemical cell, there can either be a conversion of chemical energy to 
    electrical energy, or the other way around 
    ● There are two main types of electrochemical cells 

    Voltaic Cells   Electrolytic Cell  

    Chemical to electrical   Electrical to chemical  

    Spontaneous   Non-spontaneous  

    AnOX and CatRed  AnOX and CatRed 

    LOAN   ANODE POSITIVE  


    - Left Oxidation ANODE NEGATIVE   CATHODE NEGATIVE 
    - CATHODE POSITIVE   - Anions (-ve ions) go to ANODE   
    - Exothermic 
     
    Electrodes 
    ● An ​electrode​ is a conductor of electricity used to make contact with a non-metallic 
    part of a circuit, such as the solution in a cell ​(electrolyte) 
    ● Electrochemical cells contain two electrodes, ​anode​ and the ​cathode 
    Cell Diagram 
    ● Cell Diagrams​ are used as shorthand notation to represent a voltaic cell. By 
    convention, anode is always of left, and cathode on right. The salt bridge is 
    represented by two parallel lines 
    ● Zn​(s)​|Zn​2+​(aq)​||Cu​2+​(aq)​|Cu​(s) 
     
     
     
     
     
     
     
     
    Types of Cells 
    1. Voltaic (Galvanic) Cells 
    ○ Consists of two half-cells. These two are separated, connected only by 
    a salt bride. Oxidation occurs at one half-cell (anode), reduction occurs 
    at on half-cell (cathode) 
    ○ There are different types of electrodes used in voltaic cells, most 
    common one is​ metal/metal ion electrode 
    ○ Metal/metal ion electrode 
    ■ Consists of a bar of metal placed in a solution containing 
    cations of the same metal. Examples include: 
    1. Zn​(s)​|Zn​2+​(aq) 
    2. Cu​(s)​|Cu​2+​(aq) 

    3.  

    ■ The vertical line represents a​ phase boundary 


    (junction) 
    ■ Salt bridge ​which connects both electrodes has multiple 
    functions: 
    1. Provides physical separation of reduction 
    and oxidation processes 
    2. Provides electrical continuity for anions 
    and cations 
    3. Reduces the ​liquid-junction potential. 
    This is the voltage generated when two 
    different solutions come into contact with 
    each other 
    ■ Salt bridge ​contains a concentrated solution of a strong 
    electrolyte. The high concentration allows ions to diffuse 
    out of it. The ions in a salt bridge must be inert 
    ■ To determine which metal will be oxidized, or which will 
    be reduced, refer to the activity series. Zinc is higher up 
    on series than copper thus it is more easily oxidized. The 
    zinc half-cell acts as the anode. 
    ○ Voltaic Cell example:

     
    2. Electrolytic Cells 
    ○ Electrolytic cells consist of a container of electrolyte, two electrodes, 
    and a battery which is considered an electron pump 
    ○ There are many types of electrolytic cells, most common one is ​molten 
    salt​ cell 
    ○ Molten Salt Electrolysis 
    1. Identify all species 
    2. Identify species attracted to cathode (negative 
    electrode) and anode (positive electrode) 
    3. Deduce the two half-reactions taking place at each 
    electrode, and overall cell reaction 
    4. Draw and annotate electrolytic cell and show direction 
    of electrons and of ions 
    5. State what would be observed at each electrode 
    ○ Electrolytic Cell example: 
     

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