Electrochemistry

• In an electrochemical cell, oxidation occurs at the anode and reduction occurs at the cathode.
• Electrochemistry studies the conversion of chemical to electrical energy and vice versa
• It deals with oxidation/reduction reactions that either produce or utilize electrical energy
• Oxidation and Reduction occur simultaneously
• Oxidation is the process of electron loss
• Reduction is the process of electron gain
• Oxidation leads to an increase in oxidation number
• Reduction leads to a decrease in oxidation number
• An oxidising agent is an acceptor of electrons
• A reducing agent is a donor of electrons
• An oxidising agent is reduced
• A reducing agent is oxidised
• A redox reaction is the sum of two half reactions - a reduction and an oxidation
• In a reduction half reaction, electrons are gained
• In an oxidation half reaction, electrons are lost
• The reduced and oxidised species in a half reaction form a redox couple
• A redox couple is denoted Ox/Red
• Oxidation Is Loss of electrons (OIL)
• Reduction Is Gain of electrons (RIG)
• Electrolysis is the decomposition of a compound by passing an electric current
• In electrolysis, electrical energy is used to produce chemical change
• Reduction occurs at the cathode while oxidation occurs at the anode
• Cations (positive ions) migrate to the cathode while anions (negative ions) move to the anode
• The electrode is the metal strip or wire where reduction or oxidation occurs
• The anode is the negative electrode where oxidation occurs
• The cathode is the positive electrode where reduction occurs
• Electrons flow from anode to cathode
• An electrolyte is a solution or molten that can conduct electric current
• A salt bridge connects the electrolytes; ensuring electrical contact between them
• It is made up of a gel permeated with the solution of an inert electrolyte
• It prevents the electrolytes from mixing
• It maintains the electrical neutrality of the half-cells as ions flow into and out of it
• Spontaneous oxidation/reduction reactions generate electric currents in a galvanic or voltaic cell
• The processes in galvanic cells are the reverse of those in electrolytic cells
• A battery has one or more galvanic cells, which convert chemical energy into electrical energy
• Single-cell batteries contain one galvanic cell
• Multi-cell batteries consist of several galvanic cells linked in series to obtain the desired voltage
• In a galvanic (or voltaic) cell, the cathode is positive whereas the anode is negative
• Types of batteries:

  • Lead Storage Battery
  • Zinc Dry Cell
  • Alkaline Dry Cell
  • Mercury Dry Cell
  • Nickel-Cadmium Battery
  • Nickel-Metal-Hydride (NiMH)
  • Lithium Ion (Li-ion) Battery
• Lead Storage Battery (Car battery) consists of six individual cells connected in series