Presentation on theme: "Electrochemical & Voltaic Cells"— Presentation transcript:
1Electrochemical & Voltaic Cells Notes: (21.1)An electrochemical cell is a device that either changes chemical energy to electrical energy or electrical energy into chemical energy. The change in driven by oxidation/reduction reactions (redox) which follows the activity series of metals.
2Voltage Voltage is the measure of energy available to move electrons. Sometimes called potential difference (electrical PE)Measured in volts (V) (1Joule/coulomb)The higher the voltage, the more energy each electron carriesIn order for there to be voltage there must be a continuous replacement of charge. (battery, power plant, electrochemical cell)
3Voltaic CellsA voltaic cell operates as redox reactions spontaneously occur between two different materials (usually metals).Provides a steady electric current from chemical energy.the reaction is driven by the cell (electron) potentialthe difference in the amount of electrons (charge) within each cell connected by a conductormeasured in volts (V)voltage is the measure of the potential size or force of the charge (also known as potential difference)can be determined by the difference in the half-cell reduction potentials
4Voltaic Cells – Reduction Potential can be determined by the difference in the half-cell reduction potentialsmeasured at standard conditions; 1M, 25oC, and 1 atmanode (oxidation ) is represented by a negative numberelectrons are produced - charge on the element becomes more positiveZn(s) g Zn2+(aq)+ 2e-cathode (reduction ) is represented by a positive numberelectrons are consumedcharge on the element becomes more positiveCu2+(aq) + 2e- g Cu(s)the greater the absolute value between the two potentials, the greater the voltage that is generated0.35 – (-0.76) = 1.1V
5Half Cell Reactions Anode Cathode The zinc is broken (oxidized) down to release ions (Zn2+) in the electrolyte solution (ZnSO4)Zn(s) g Zn2+(aq) + 2e-CathodeThe copper is built up (reduced) absorbing ions from the electrolyte solution (CuSO4)Cu2+(aq) + 2e- g Cu(s)Each ½ cell is connected through a conductorThe excess electrons then flow from the anode (negative zinc terminal) through the conductor to the cathode (positive copper terminal) and then back through the electrolyte solution to the zinc terminal.The salt bridge is created to separate the two metalsdifferentially allows ions and electrons to travel from one compartment to another while keeping the metals separateseparates the two half-cells of the batteryeach half-cell contains ~ the same ratio of + & - ions as long as the circuit is connected