A. In Daniel cell of Cu2+ and Zn2+ ions, E(cell) increases with increase in the concentration of Cu2+ ions and decreases with increase in the concentration of Zn2+ ions. The electrode potential for any given concentration of Zn2+ ions is given as E(Zn2+/Zn) = Eo(Zn2+/Zn) -RT/2Fln1/[Zn2+(aq)]. The reaction at anode with lower value of Eo is preferred and therefore, water should get oxidised in preference to Cl– (aq). [NCERT Exemplar] Answer/Explanation. E(cell) depends on the concentration of both Cu2+ and Zn2+ ions. which corrodes itself but saves the other object. The reaction with higher value of E0 is preferred. Reason : For weak electrolytes degree of dissociation increases with dilution of solution. The charge on 1g of Mn4+ ion is 3.85 × 105 C. Charge on one ion of Mn4+ = 4 × 1.6 × 10-19 C Thus, charge on one g ion of Mn4- = 4 × 1.6 10-19 × 6.02 × 1023 = 3.85 × 105 C. The cell potential is the difference between the electrode potentials of the cathode and anode and is called the cell electromotive force of the cell, when no current is drawn through the cell. It cannot be unity. Chemistry MCQs for Class 12 Chapter Wise with Answers PDF Download was Prepared Based on Latest Exam Pattern. An electrochemical method is to provide a sacrificial electrode of another metal (like Mg, Zn, etc.) The conductivity of pure water is 3.5 × 10-5 Sm-1. It is also known as redox couples. Assertion: Am for weak electrolytes shows a sharp increase when the electrolytic solution is diluted. The cation Na+ is reduced at the cathode Na+ + e– → Na and one anion Cl– is oxidised at the anode Cl–→ ½Cl2+e– to give sodium metal and chlorine gas. This is Faraday's first law of electrolysis. With the increase in dilution, the degree of dissociation increases and as a result molar conductance increases. Besides Na+ and Cl– ions, we also have H+ and OH– ions along with the solvent molecules, H2O in aqueous sodium chloride solution electrolyses to give the products NaOH, Cl2 and H2. Depending on the magnitude of conductivity, the materials are classified in to conductors (metals), insulators (glass, ceramics), semiconductors (silicon, doped silicon) and super conductors (ceramic material, mixed oxides). The limiting value of molar conductance corresponds to degree of dissociation equal to 1 i.e., the whole of the electrolyte dissociates. Solution : In weak electrolyte the degree of dissociation is very small. One mole of Mg2+ requires 2 moles of electron that is 2 Faraday. Inert electrodes do not participate in the reaction but provide their surface for oxidation or reduction reactions and for the conduction of electrons. 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Electrical conductance through metals is called metallic or electronic conductance and is due to the movement of electrons. The cell reaction for the given cell can be written as: 2Al(s) + 3Fe2+ →2Al3+ + 3Fe(s) 6 moles of electrons are involved in the process. The two different portions of the Daniell cell on which the two half reactions occurs are called as half-cells. The degree of dissociation of week electrolyte increases as_____? For the transfer of 1 mole of electrons, the quantity of electricity flowing = 1F then, For the transfer of n mole of electrons, the quantity of electricity flowing = nF. The change in molar conductivity for weak electrolytes with dilution is due to increase in degree of dissociation. Chemistry MCQs for Class 12 Chapter Wise Your email address will not be published. Faraday published his results during 1833-34 in the form of Faraday’s two laws of electrolysis. Acetic acid is an example of a weak electrolyte. Gold is also used as inert electrode. Free PDF Download of CBSE Chemistry Multiple Choice Questions for Class 12 with Answers Chapter 3 Electrochemistry. During the electrolysis of aqueous sodium chloride solution, the products are NaOH, Cl2 and H2. The other half-cell in which reduction takes place is called cathode and it has a positive potential with respect to the solution. The number of mole of electrons required for the reduction of one mole of Mg2+ ions are 2e-. However, on account of over-potential of oxygen, reaction Cl- (aq) → 1/2Cl2 (g) + e- is preferred. 0 votes . The cell potential is given by Eo = EoR - EoL As EoL for standard hydrogen electrode is zero, Eo = EoR – 0 = EoR. During the electrolysis of aqueous sodium chloride, oxidation of chloride ion is preferred at anode due to over-potential of oxygen. Thus, there exists a potential difference between the electrodes. It is also represented as emf. Bisphenol is commonly used to prevent corrosion in the cans used for storage of food and beverages. 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