The water is decomposed into oxygen (O2) and hydrogen gas (H2) due to the flow of current in the water.
The current is 3A, and the process lasts 36 hours.
We should calculate the number of moles of electrons of the water.
These relations help:
Amperes x time= Coulomb
1 Faraday=96.485 Couloms
1 Farady= 1 mole of electron
1 mole of electron= 9.11 X 10^-31 Kg
So, the number of moles of electrons of the water that is decomposed is:
3 A x 129600 seconds
And the weight is: 3 A x 129600 seconds x 9.11 X 10^-31 Kg