16379.DOC-SKEngineeringAcademy.doc

UNIT I – ELECTROCHEMISTRY (PART A) What are the conditions for a cell to be reversible? A cell will be reversible if it satisfies the following conditions, i) If Eappl =Ecell , no chemical reaction takes place ii) If Eappl Ecell , chemical reaction will take place in reverse direction Define standard electrode potential. The measure of tendency of a metallic electrode to lose or gain electrons when in contact with a solution of its own salt of 1M concentration at 25 ° C . Give the Nernst equation. For an electrode reaction, Mn+ (aq) + n e- ( M (s) The Nernst’s equation is , E Mn+/ M = E0 Mn+/ M +2.303RT/nF log [ Mn+ ] Significance of Nernst equation? i. Used to calculate the single electrode potential. ii. Polarity of the electrode in an electrochemical cell can be determined. What are conductometric titrations? A method of estimation of strength or the endpoint with the measurement of change in conductance of the solution is called conductometric titration. The conductance depends on the number and mobility of the ions. Distinguish between reference electrode and indicator electrode. Reference electrode Indicator electrode It is a standard half cell used to measure single electrode potential of various metals placed in electrolytes. Its electrode potential is zero. It responds rapidly and reproducibly to change in the concentration of electrolyte Eg. Standard hydrogen electrode. Glass electrode. What are the advantages of glass electrode used in pH determination? i) It can be used in any solutions with pH = 0 to 10 ii) A small quantity of solution is sufficient for the determination of pH. Calculate the reduction potential of Cu/Cu2+ (0.5 M) at 25oC. given that Eo= 0.337: (Cu 2+= 0.5M) E=Eo + log [Cu2+] ; E=0.337 + ; E= 0.3281 V Differentiate between electrolytic cells and galvanic cells? (Nov. 2005), (May 2003) Sl No Electrolytic cells Electrochemical cell 1 Electrical energy is converted into chemical energy. E