Title 1. ELECTROCHEMISTRY (1-102).pmd.pdf ✅

X–Chemistry (Vol–I) 2 Narayana Group of Schools Olympiad Class Work Book Michael Faraday [1791 – 1867] Electro chemistry Michael Faraday was an English scientist who contributed to the study of electromagnetism and electro chemistry. His main discoveries include the principles underlying electromag- netic induction, diamagnetism and electrolysis. As a chemist, Faraday discovered benzene, investigated the clathrate hydrate of chlorine, invented an early form of the Bunsen burner and the system of oxidation numbers, and popularised terminology such as "anode", "cathode", "electrode" and "ion". Faraday ultimately became the first and foremost Fullerian Professor of Chemistry at the Royal Institution, a lifetime position.
X – Chemistry (Vol – I) Olympiad Text Book 3 Narayana Group of Schools Olympiad Class Work Book ELECTRO CHEMISTRY Introduction: Electro chemistry is a branch of physical chemistry which deals with the relationship between chemical energy and electrical energy and how one can be converted into another. (OR) The branch of science which deals with the production of electricity from energy released during spontaneous chemical reactions and the use of electrical energy to bring about nonspontaneous chemical transformations is called “Electro Chemistry”.  It is broadly divided into two types i)Production of chemical change by electrical energy (Phenomenon of electrolysis) ii)Conversion of chemical energy into electrical energy (i.e generation of electricity) by spontaneous redox reactions.  The basis of above two processes are Redox reactions i.e. these processes involve transfer of electrons. Electric current : Electric current is considered as “the flow of electrons or flow of electrical charges (ions) through a conducting medium”. Substances Electrical Conductors [Allows passage of current through them] Electronic Conductors (OR) Metallic Conductors Electrolytic Conductors Insulators [Don’t allow passage of current]  All substances do not conduct electric current. Conductors : The substances which allow the passage of electric current through them are called “ Electrical conductors” or simply “conductors”.
X–Chemistry (Vol–I) 4 Narayana Group of Schools Olympiad Class Work Book Example: Aqueous solutions and molten (fused) state of salts , acids, bases and metallic conductors like (Cu, Zn, Al). Insulators : The substances which does not allow the passage of electric current through them are called “Insulators” . Example: Rubber, glass, ceramics, non-metals (except graphite), plastics. Types of electrical conductors :  Electrical conductors are of two types (i) Electronic conductors (or) Metallic conductors  These substances which allow the electricity to pass through them without undergoing any chemical change are known as electronic or metallic conductors.  The flow of electric current through metallic conductors is due to the flow of electrons. Example:(a) Metals and their alloys (b) Non metals like Carbon black, graphite. (c) Organic polymers like poly aniline, poly pyrrole, polythiophene, poly acetylene when exposed to vapours of Iodine. (d) Salts like CdS, CuS (Electronic conduction of CdS and CuS is due to crystal defect or interstitial defect).  Metals and their alloys, at very low temperatures (0 to 15K) were known to be- have as “super conductors”.  Ceramic materials and mixed oxides also show super conductivity at temperature as high as 150K. Super conductivity : The ability of certain materials to conduct electric current with practically zero resistance at low temperature, This is first time observed by H.K onnes in 1911 , a Dutch physicist. Example: Hg, Pb, Alloys (Nb-Ti, Ge-Nb) Niobium nitride, Ceramics MgB2 and Organic materials like Fullerene C60  , carbon Nano tubes. Ceramic materials used to make super conductors are a class of materials called perovskites composition of (Y) (Ba) (Cu) acts as superconductor at 90K. Electronic conductance depends on : (a) The nature and structure of the metal (b) The number of valence electrons per atom (c) Temperature (it decreases with increase of temperature) (ii) Electrolytic conductors (Ionic conductance)  The substances which allow the electricity to pass through them by undergoing chemical decomposition are known as electrolytic conductors or electrolytes.  The conductance of electrolytic conductors is due to flow (or movement) of ions towards oppositely charged electrodes. Therefore it is also known as Ionic conductance.