Question

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

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

Answer 1

The correct option is D 3.2 hours

$B_2{H}_6+3O_2\to B_2{O}_3+3H_{2}O$
According to the balanced equation, 27.66 g of $B_2{H}_6$ i.e., 1 mol of $B_2{H}_6$ require 3 mol of $O_2$, which is obtained by the electrolysis of water.

On electrolysis of water,
$2H_{2}O\to O_2+4H^{+}+4e^{-}$
1 mol of $O_2$ is produced by 4F charge.
Then, 3 mol of $O_2$ will require 12 F charge.
Now applying,
$Q=It$
$12\times 96500=100\times t\left(s\right)$
$\Rightarrow t=\frac{12\times 96500}{100\times 3600}$
$\Rightarrow t=3.2hours$