electrolysis

Question 1

why is silica crucible used as an electrolytic cell in the electrolysis of molten lead bromide?

Answer 1

i) it is non-reactive
ii) almost a non-conductor of electricity
iii) can withstand high temperatures

Question 2

why is molten lead bromide used as the electrolyte in the electrolysis of molten lead bromide?

Answer 2

i) solid lead bromide has ions held together by strong electrostatic forces of attraction thus it is a non-conductor of electricity
ii) in molten lead bromide the ions become free easily making it a good conductor of electricity
iii) crucible is heated from the outside to keep lead bromide in the molten state

Question 3

why is graphite used as an inert electrode in the electrolysis of molten lead bromide?

Answer 3

i) graphite electrode is an inert electrode which is used so that it doesn’t react with the products during electrolysis
ii) graphite electrodes are used over platinum electrodes because the platinum electrodes react with the bromine vapours evolved at the anode

Question 4

what is the temperature of the electrolyte in the process of electrolysis of molten lead bromide?

Answer 4

temperature is above 380 degrees Celcius

Question 5

why is the temperature of electrolyte in the process of electrolysis of molten lead bromide kept so?

Answer 5

this is because already fused PbBr2 has a tendency to solidify

Question 6

how much electricity is supplied to electrolysis of molten lead bromide

Answer 6

12v and 3 amps

Question 7

what is the product formed at the cathode in the case electrolysis of molten lead bromide

Answer 7

i) molten lead metal around the cathode is silvery grey
ii) the molten lead metal settles down at the base of the crucible as it is heavier than the lead bromide and is in liquid state

Question 8

what is the product formed at the anode in the case electrolysis of molten lead bromide

Answer 8

i) reddish brown bromine vapours are formed at the anode

ii) the bromine vapours are formed at a high temperature of about 380 degrees celcius

Question 9

what is the elecrolytic cell used in the electrolysis of acidulated water using platinum electrodes

Answer 9

Hoffman’s voltameter

Question 10

why is hoffman’s voltameter used in the electrolysis of acidulated water using platinum electrodes

Answer 10

i) it consists of 3 tubes

the first tube is used to supply acidulated water
the side tubes are used for collecting the products of electrolysis

Question 11

what is the electrolyte used in the electrolysis of acidulated water using platinum electrodes

Answer 11

distilled water containing a small amount of sulphuric acid

Question 12

why is distilled water containing a small amount of sulphuric acid used in the electrolysis of acidulated water using platinum electrodes

Answer 12

i) pure water is a very weak electrolyte and the addition of sulphuric acid helps in the ionisation of water molecules making it a good conductor of electricity
ii) dilute sulphuric acid is preffered to nitric acid as nitric acid is very volatile and interfers with the electrolytic reaction

Question 13

why are inert platinum electrodes used in the electrolysis of acidulated water using platinum electrodes

Answer 13

they are used so that they dont react with the products formed during electrolysis