Shaillee Kaushal is teaching live on Unacademy Plus
Electrochemistry - V XII - 03
Electrochemical cell:- An electrochemical cell is a system or arrangement in which electrodes are fitted in the same electrolyteor in two different electrolytes joined by a salt bridge It is of two types: (a) Electrolytic cell: Electrolysis is caried out by passing electricty In this the reactions are non-spontaneous. Electrical energy is converted into chemical energy b) Galvanic or voltaic cell: In this redox reaction is used to convert chemical energy to electrical The chemical reaction is responsible for production of electricity takes place in two energy separate compartments The compartments containing the electrodes and the solution of the electrolyte are called half cells.
Daniel Cell Flow of electrons Zinc Copper Cutrent flow (Anode Zinc sulphate solutior ZnSO Cathode Copper () Salt bridge solution Cotton wool plug Anion movement Cation movement
Difference in electrolytic cell and galvanic cell: Electrolytic cell (1) Electrical energy is converted into chemical energy Galvanic cell (1) Chemical energy is converted into electrical energy (2) Anode is positively charged and cathode is negatively charged. 2.Anode is negatively charged and cathode is positively charged (3) Ions are discharged on both the electodes 3.Ions are discharged only on the cathode (4) Both the electodes can be fitted in the 4.The electodes are fitted in different comparments. same compartment
Salt Bridge and its significance:- Salt Bridge is usually an inverted U-tube with concentrated solution of inert electolytes ike KCI, KNO3, NH,NO3 etc >For the preparation of salt bridge, gelatin or agar-agar is dissolved in wet concentrated solution of aqueous solution of inert electolyte and the solution is filled in the U tube. The and of the U tube are plugged with cotton wool as to minimise diffusion
Significance ofsalt Bridge: (i) It connects the solutions of two halt cells and complete the cell circuit. (ii It prevents transference or diffusion of the solutions from one half cell to the other. (iii It keeps the solution in two half cells electrically neutral (iv) It prevents liquid-liquid junction-potential i.e the potential difference which arises between two solutions when in contact with each other.
Representation of an electrochemical cell: The Daniel cell is represented as 2+ Cu