How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane?
(Atomic weight of B = 10.8 u)

Options

A. 6.4 hours
B. 0.8 hours
C. 3.2 hours
D. 1.6 hours

Answer

C

Explanation

`B_(2) H_(6) + 3 O_(2) to B_(2) O_(3) + 3H_(2) O`
`27.66` g of `B_(2) H_(6)` (1 mole) requires 3 moles of oxygen `(O_(2))` for complete burning .
Required `O_(2)` (3 moles) is obtained by electrolysis of 6 moles of `H_(2)O`
On electrolysis : `6 H_(2) O to 6 H_(2) + 3 O_(2)`
Number of Faradays = 12 = Amount of charge
`12 xx 96500 = i xx t`
`12 xx 96500 = 100 xx t`
`t = (12 xx 96500)/(100)` second = `(12 xx 96500)/(100 xx 3600)` hour
= 3.2 hours