S1 B.Tech Group A&B Chemistry for Information & Electrical Science - Franklin's lectures PDF

CHEMISTRY FOR INFORMATION AND ELECTRICAL SCIENCE Group A & B CHEMISTRY FOR INFORMATION AND ELECTRICAL SCIENCE Group A & B Module 1 ? What is galvanic series? How is galvanic series advantageous over electrochemical series in corrosion chemistry?  G...

CHEMISTRY FOR INFORMATION AND ELECTRICAL SCIENCE Group A & B CHEMISTRY FOR INFORMATION AND ELECTRICAL SCIENCE Group A & B Module 1 ? What is galvanic series? How is galvanic series advantageous over electrochemical series in corrosion chemistry?  Galvanic Series The electrochemical series gives useful information regarding the reactivity - - of - metals, but it does not provide sufficient information in predicting the - corrosion behavior. - In electrochemical series, the metals having lower reduction potential in the - - series are more anodic and undergo corrosion faster. - Lowt Oxid" > Anode R4 Reduction > Cathode R P Hish = -. 2) Galvanic series is a series in which the metals and alloys are - 3 arranged in the order of their corrosion tendencies. - A metal high in the series is more anodic and undergo -- corrosion faster - Comparison between electrochemical series and galvanic series T Electrochemical series Galvanic series O O E is measured for metals and non- - E is measured for metals and alloys - - - metals - D ⑧ E is measured by dipping pure E is measured by dipping metals metals in their 1M salt solution. and alloys in unpolluted sea water. - SHE is used as reference electrode - Calomel electrode is used as - reference electrode Position of a metal is fixed. Position of metal and alloy may - change - - It predicts the relative It predicts the relative corrosion - displacement tendencies tendencies - & ? Why full charging is not allowed in Li-ion cell? O Li-ion cell - In lithium ion cell, the positive electrode is made by using a - - - crystalline mixed oxide LiCoO2, or Li2O.Co2O3. - - - -- The negative terminal is made of graphite. - - A solid electrolyteseparator (SEI) separate the anode and cathode - - - - compartments - Nasar nuae Li -cit.  Charging: - During charging the cell act as an electrolytic cell, the electrical energy is - 2 converted into chemical energy O - Lio , Y Anode (+) LiCo02 → ↳ + + ne E - - Li , On t 2  Here x < 1 mole, say 0.9 (or 90 percentage) - = ie, some Li+ ions get removed from the crystal lattice, In the respective lattice sites Co3+ ion get oxidized to Co4+and. electrical neutrality is maintained in the lattice Cathode (-) The Li ion produced at the anode get migrated through the electrolyte and --- get reduced to lithium atom at the graphite electrode. -- CG + x Li+ + xe → LixCG se- Lia(a Gastuci +  Li atoms are inserted between the layers of carbon atoms. This so called lithiated graphite is written as LixCG, containing no Li metal as such. This is why Li-ion battery is not called as Li battery.  When Lithium ion cells are allowed to charge completely (x=1) - - anodic material becomes Li1-1CoO2 or CoO2, which is an --- F - explosive material (due to liberation of O2 gas on decomposition). - Therefore automatic built-in circuit breakers are there inside - -- battery which allows charging only up to 90 percentage (x= 0.9) ? How is electroless copper plating done? Write the reactions -- involved? - Electroless Copper plating Electroless copper plating is used to deposit a layer of copper on a - substrate - without the use of electrical energy. It is commonly used for making printed circuit boards. - The object to be plated is degreased using organic solvent followed - -- by acid treatment. ① - This object is then immersed in plating bath containing cupric salt, - - - = reducing agents, buffer and complexing agent - - -- - - - Process of electroless plating: The process of electroless plating involves the following steps. G 1. Preparation of the surface to be plated 2. Preparation of plating bath 1. Preparation of the surface to be plated: - In this step the surface is activated by following ways - 1. Etching- Removal of impurities by acid treatment - - 2. Electroplating - A thin layer of the metal to be plated or any other - suitable metal is coated on the surface of the object. - 3. - Chemical Treatment 2.Preparation of plating bath: - The plating bath should include the following -cupric salt reducing agents - Cncno) buffer - complexing agent - Anode Coxiat - = () Acro thou > - 200 + 12 +210 e 2 - = Base formaldehyde = = +0. 056V = = - Cathode = Creduction) + ( Electroless copper solutions:- - Utilizing formaldehyde as reducing agent - - - - - Employ high pH, above 12 (typical NaOH concentration is > 0.1N) - - - - = - - Applications of electroless copper plating - This type of coating is mainly used in double or multilayered printed - - circuit boards in which plating through holes is required. - This is used as base coating for subsequent electroplating - ? Explain Fuel cell with an example O Fuel Cells cremia Electo A fuel cell is a galvanic cell in which the chemical energy of a fuel is - - directly converted to electrical energy. - It differs from ordinary electrochemical cell in the sense that, here the - - reactants are supplied from outside rather than forming an integral part of -- the cell and the energy should be withdrawn indefinitely from a fuel cell as - -- long as the outside supply of the fuel is maintained. - Hydrogen-Oxygen Fuel Cell (acid electrolyte) - Hydrogen-oxygen fuel cell produces electricity based on the following - exothermic reaction - - 2H2(g) + 02(g) → 2H20(l) + Ener - F =  Here hydrogen acts as the fuel and oxygen acts as the - - oxidant. Il - It consists of two electrodes made up of porous graphite, - - soaked with metal catalysts such as platinum. : - Arhhenius acid like phosphoric acid is generally employed - - - - as the electrolyte. - -  Hydrogen and oxygen gas under pressure (50 atm) are - - -- continuously passed through the anodic and cathodic - - chambers respectively. - The cell operates at about a temperature of 150 - 200°C, - since the ionic conductivity of phosphoric acid is very low at - - - low temperatures. - Heat is generated during the reaction of hydrogen with oxygen, and so cooling plates are used to maintain a cell - - > - & operating temperature of about 200°C. - m (50th) (Sort) At anode: - - Hydrogen is oxidized to H+ ions at the anode and the electrons formed will flow through the external circuit to the cathode. 212- 4hT +He E = o E H2  At cathode:.H+ ions from the electrolyte are transported to the oxygen compartment and combines with oxygen gas and electrons to form water. H+ ion deficiency at the electrolyte side is balanced by the - - n H+ ion formed at the anode. - Water formed is drained out through the oxygen compartment side - 82 +qut + He > 2120 - E= 1. 23Y P Anode reaction Coxid") an - > u ++ (e E = o Cathode reaction E 25 tunt 1 nee =. > ~ - + Net reaction 1 23 E : -> 2120 = Out 21 - - Advantages of hydrogen - oxygen fuel cell - The fuel cell has high efficiency and can convert about 80% - of available chemical energy to electrical energy. It does not cause any pollution since the only byproduct is - water and they are free of noise, vibration, heat transfer etc - -  Used in space craft due to its light weight and the byproduct water is used for - - drinking in space stations. - It can supply energy continuously as long as the reactants are fed. - - The concentration of the electrolyte remains unchanged. - It is simple and easy to operate - Disadvantages of hydrogen - oxygen fuel cell - There is difficulty in getting a suitable electro- -- catalyst which can function efficiently for long periods - - without getting contaminated - Gaseous fuels are difficult to store and handle. - The electrolyte used is highly corrosive. - Fuels used must be extremely pure. - The technology is expensive. -  B 2 ? Explain the construction and working of a calomel electrode as a - - - reference electrode -  Calomel Electrode - Calomel electrode is a secondary reference electrode. - This is a commonly used reference electrode since it is difficult to set up and - maintain SHE. - - This is an example of metal-metal insoluble metal salt electrode and a solution of its common ion (mercury-mercurous chloride electrode, KC1). Construction: - It consists of a glass tube at the bottom of which a small amount of Hg is placed. -- This is covered with a paste of solid mercurous chloride (Hg2Cl2 or calomel) = - - which is further in contact with a solution of KCI. O - A Pt wire dipped into the Hg layer is used for making electrical contact. = -- - The side tube is used for making electrical contact with a salt bridge. The electrode may be represented as G Hg(Ng2/kC - The electrode reaction is given by -2g - My + ze + 2(1gy (Red") => Cathode  ⑭ & KCl concentration = O 0.1N (DNCE) D 1N (NCE) SATURATED (SCE) Electrode potential (V) O 0.3335 - = 0.2810 0.2422  The potential of the calomel electrode varies with the concentration of the - KCl solution. - Saturated calome electrode is generally used, since it is easy to setup and - - - - its emf will not change with chemical reaction. - Working : = The calomel electrode can act as anode or cathode depending on the electrode - - - potential of the coupled electrode. - If the electrode potential of the coupled electrode is lower than the calomel - = - electrode, then calomel electrode undergoes reduction and act as cathode. => 192C , ->gas ~ untze Ange E Calmel P MallCT 24g(s R Auch) - + (2) Oxid or  If the potential of the coupled electrode is greater, calomel electrode will undergo Wy oxidation and the reverse reaction takes place. te Palomel Rephip R P. ↓ Ced") Loxid) Anode eathode =  logs = noge - The Nernst equation of this electrode at 25°C is given by I Econ = Ece-59 by Ecal = Ecol-oloy Ecl = Eco-log