1.

8.2 xx 10^(12) litres of water is available in a lake. A power reactor using the electrolysis of water in the lake produces electricity at the rate of 2 xx 10^6 Cs^(-1) at an appropriate voltage. How many years would it like to completely electrolyse the water in the lake. Assume that there is no loss of water except due to electrolysis.

Answer»

Solution :Hydrolysis of water:
At anode: `2H_2O to 4H^+ + O_2 + 4E^(-) "" …………..(1)`
At cathode: `2H_2O + 2e^(-) to H_2 + 2OH^(-)`
Overall reaction : `6H_2O to 4H^+ + 4OH^(-) + 2H_2 + O_2`
(or)
Equation `(1) + (2) xx 2 implies 2H_2O to 2H_2 + O_2`
`:.` ACCORDING to Faraday.s Law of electrolysis, to electrolyse two mole of Water
`(36g ~= 36 mL " of " H_2O)`, 4F charge is required alternatively, when 36 mL of water is electrolysed,the charge generated = `4 xx 96500 C`.
`:.` When the whole water which is avialable on the lake is completely electrolysed the amount of charge generated is equal to
`(4 xx 96500 C)/(36 mL) xx 9 xx 10^(12)L = (4 xx 96500 xx 9 xx 10^(12))/(36 xx 10^(-3)) C = 96500 xx 10^(15) C`
`:.` Given that in 1 second, `2 xx 10^(6) C` is generated therefore, the TIME required to generate
`96500 xx 10^(15) C is = (1S)/(2 xx 10^6C) xx 96500 xx 10^(15) C = 48250 xx 10^9S`
`:. ` Number of years = `(48250 xx 10^9)/(365 xx 24 xx 60 xx 60) "1 year= 365 years "`
`= 1.5299 xx 10^(6) "years" = 365 xx 24` hours
`"" = 365 xx 24 xx 60` min
`"" = 365 xx 24 xx 60 xx 60 `sec.


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