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CBSE Class 12-science Answered

Cr metal can be placed out from an acidic solution containing CrO subscript 3 left parenthesis aq right parenthesis space plus space 6 straight H to the power of plus left parenthesis aq right parenthesis space plus space 6 straight e with minus on top space rightwards arrow Cr left parenthesis straight s right parenthesis space plus space 3 straight H subscript 2 straight O Calculate (i) how many grams of Cr will be plated out by 24000 C?                 (ii) how long will it take to plate out 1.5g of Cr by using 12.5 A current?  
Asked by sunil2791 | 19 Jan, 2018, 12:21: PM
answered-by-expert Expert Answer
left parenthesis straight i right parenthesis CrO subscript 3 space plus space 6 straight H to the power of plus space plus space 6 straight e to the power of minus space rightwards arrow space Cr space plus space 3 straight H subscript 2 straight O space The space straight n space factor space equation space is comma space straight Q space equals space space left parenthesis straight n asterisk times space nf right parenthesis straight F space straight Q space equals space Amount space of space charge space required space straight n space equals space no. space of space moles space of space the space species space nf space equals space straight n space factor space straight F space equals space 96500 space straight C therefore space 24000 over 96500 space equals space straight n to the power of asterisk times space 6 For space Cr space straight n space factor space is space 6. therefore space straight n space equals 0.0414 space mol Molar space mass space of space Cr equals space 52 space therefore space 52 cross times 0.0414 space equals space 2.15 space straight g CrO subscript 3 space plus space 6 straight H to the power of plus space plus space 6 straight e to the power of minus space rightwards arrow space Cr space plus space 3 straight H subscript 2 straight O space The space straight n space factor space equation space is comma space straight Q space equals space space left parenthesis straight n asterisk times space nf right parenthesis straight F space straight Q space equals space Amount space of space charge space required space straight n space equals space no. space of space moles space of space the space species space nf space equals space straight n space factor space straight F space equals space 96500 space straight C therefore space 24000 over 96500 space equals space straight n to the power of asterisk times space 6 For space Cr space straight n space factor space is space 6. therefore space straight n space equals 0.0414 space mol Molar space mass space of space Cr equals space 52 space therefore space 52 cross times 0.0414 space equals space 2.15 space straight g left parenthesis ii right parenthesis Charge space equals space current space cross times space Time space therefore space 12.5 space left parenthesis straight t right parenthesis equals space fraction numerator 1.5 over denominator 52 end fraction cross times 6 cross times 96500 space space space space space space space space space space space space space space space space space space straight t space equals space 1336.15 space sec
Answered by Varsha | 20 Jan, 2018, 02:21: PM

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