Q. 265.0( 1 Vote )

(a) A cell is pre

Answer :

(a) The Ecell decreases.


Explanation:


As we know the Ecell of a cell is calculated by the Nerst equation:
E(Zn2+/Zn) = E0(Zn2+/Zn) -


This is the equation for the cell given above:


Therefore ecell here is inversely proportional to the concentration of Zn2 + ions as we see.


Clearly, if the concentration is increased, Ecell will decrease.


(b) At the Anode: Chlorine gas is evolved.


At the Cathode: Hydrogen gas is evolved


Explanation:


in the electrolysis of aqueous NaCl,


the ions produced will be –


Na+,Cl- ,H+ and OH- released by the dissociation of NaCl and H2O respectively.


At the Cathode:
Na+ (aq) + e-
Na (s), E0(cell) = - 2.71V
H+ (aq) + e-
1/2 H2 (s), E0(cell) = 0.00 V


As the reaction with high Ecell is preferred,His released at cathode


At the anode:
Cl- (aq) 1/2 Cl2 (g), E0(cell) = - 2.71V


Chlorine gets oxidized at anode to give chlorine at the anode.


(c) The overall cell - reaction is –


Cu2 + (aq) + Ni (s) Ni2 + (aq) + Cu(s)


FORMULA TO FIND E0CELL


E0cell = E0cathode - E0anode


E0cell = 0. 34 - ( - 0. 25)


E0 = 0. 59V


FORMULA TO FIND ECELL


Ecell = E0cell - log OR Ecell = E0cell - log


Where,


n = the no. of exchanged electrons


r = gas constant


T = absolute temperature 298K


F = Faradays’s constant


Ecell = 0. 59 - log [n = 2]


Ecell = 0. 6195V


CONCLUSION


Ecell of the given cell is = 0. 6195V


OR


(a) If an electrolyte on dissociation gives cations and anions,then its limiting molar conductivity is given by,



For calcium chloride,



(b) The conductivity of the NaCl solution decreases on dilution as the number of ions per unit volume decreases.


The molar conductivity of NaCl increases on dilution as on dilution the inter - ionic interactions are overcome and ions are free to move about. This is also clearly seen in the data given above.


(c) Given,


Resistance = 100 ohms


C = 0. 1M


Cell constant G* = 1. 29 cm - 1


G* = K . R


K = = 0. 0129 S cm - 1


Formula to calculate limiting molar conductivity is =



= 129 S cm2 mol – 1


Conclusion:


The molar conductivity of the KCl solution is 129 S cm2 mol - 1


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