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Electrochemistry

Question
CBSEENCH12010986

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)

  • 1.6 hours

  • 6.4 hours

  • 0.8 hours

  • 3.2 hours

Solution

D.

3.2 hours

B2H6 + 3O2    B2O3 + 3H2O

According to the balanced equation:

27.66 g B2H6 i.e. 1 mole B2H6 requires 3 moles of O2. Now, this oxygen is produced by electrolysis of water.

2H2O 4F 2H2 + O2

1 mole O2 is produced by 4 F charge
therefore, 3 mole O2 will be produced by 12 F charge

hence, Now applying

Q = It
12 x 96500 C = 100 x t (s)

t = 12 x 96500100 x 3600 hours

t = 3.2