1.

8.2 times 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 times 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_(2)O rarr 4H^(+)+O_(2)+4e^(-) "...(1)"`
At cathode:
`2H_(2)O+2e^(-) rarr H_(2)+2OH^(-)`
Overall REACTION
`6H_(2)O rarr 4H^(+)+4OH^(-)+2H_(2)+O_(2)`
`""`(or)
Equation (1) + `(2) times 2 rArr 2H_(2)O rarr 2H_(2)+O_(2)`
`therefore` According to Faradays Law of electrolysis, to electrolyse two mole of Water `(36gcong36mL " of "H_(2)O)`, 4F charge is required alternatively, when 36 mL of water is electrolysed, the charge generated `=4 times 96500 C`.
`therefore` When the whole water which is available on the lake is completely electrolysed the amount of charge generated is equal to
`""=(4 times 96500C)/(36mL) times 9 times 10^(12)L`
`""=(4 times 96500 times 9 times 10^(12))/(36 times 10^(-3))C`
`""=96500 times 10^(15)C`
`therefore` Given that in 1 second, `2 times 10^(6)` C is generated therefore, the time required to generate
`96500 times 10^(15)C " is " =(1S)/(2 times 10^(6) times C) times 96500 times 10^(15)C`
`""=48250 times 10^(9)S`
`therefore` NUMBER of years `=(48250 times 10^(9))/(365 times 24 times 60 times 60)`
`""=1.5299 times 10^(6) years`
1 year = 365 days
`""=365 times 24` hours
`""=365 times 24 times 60` min
`""=365 times 24 times 60 times 60` sec.


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