Q2 of 37 Page 1

Read the given passage and answer the questions

A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2SO4 falls to 1.139 g mL-1. (20% H2SO4 by mass)


How much electricity in terms of Faraday is required to carry out the reduction of one mole of PbO2?



Pb has the oxidation state of +4 in PbO2 and it reduces to PbSO4 where oxidation state is +2. Thus, 2 electrons (+4 - +2) electrons are required for this reduction reaction to take place.



Since 2 electrons are accepted are used up in this reduction process, so by Faraday’s law of electrolysis,


1 mole of Pb requires 2F electricity to carry out the reduction.


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1

Read the given passage and answer the question

A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2SO4 falls to 1.139 g mL-1. (20% H2SO4 by mass)


Write the reaction taking place at the cathode when the battery is in use.


 3

Read the given passage and answer the questions

A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2SO4 falls to 1.139 g mL-1. (20% H2SO4 by mass)


What is the molarity of sulphuric acid before discharge?


 4

Read the given passage and answer the questions

A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2SO4 falls to 1.139 g mL-1. (20% H2SO4 by mass)


The lead storage battery is considered a secondary cell. Why?


 5

Read the given passage and answer the question

A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2SO4 falls to 1.139 g mL-1. (20% H2SO4 by mass)


Write the products of electrolysis when dilute sulphuric acid is electrolysed using Platinum electrodes.