The potential difference across the terminals of a battery of emf 12 V and internal resistance 2 Ω drops to 10 V when its is connected to a silver voltmeter. Find the silver deposited at the cathode in half an hour. Atomic weight of silver is 107.9 g mol–1.


Let the current through the circuit i be.



Emf of battery, E = 12 V



Voltage drop across the voltmeter, V = 10 V



Internal resistance of the battery, r = 2 Ω



Applying Kirchhoff’s Law, the algebraic sum of voltage and voltage drop in the circuit is zero,


we get



Where, E = battery emf


V=voltage drop


r=internal resistance


I = current through the circuit





Using the formula, from faraday’s law of electrolysis –



where,


m = the mass of the substance deposited on the electrode


z=electrochemical equivalence


i=current passing


t=time taken




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