Question

1g equivalent of na metal is formed from electrolysis of fused nacl find no. of moles of al from fused na3alf6

Answer 1

NaCl is electrolysed to form Na+ and Cl- ions given by the equation:

Na+ + Cl- ----> NaCl

We know that 96,500 coulombs of electricity is required to liberate 1 mol of Na+ or 23 gm equivalents of Na+.
Therefore, 1 gm equivalent of Na+ would be liberated by 96500/23 Coulombs of electricity = 4195 Coulombs

Now, the amount of electricity used is the same in the electrolysis of Na3AlF6.
No. of moles of electrons = 4195 coulombs X One mole of electrons / 96, 500 Coulombs= 0.0434 moles of e-

We know that 1 Al3+ takes 3 e-  --> to form Al metal
So, 0.0434 moles of e- X 1 mole Al / 3 mole e- = 0.0145 moles of Al