Question

What mass of Ni2+ is produced in solution by passing a current of 67.0 A for a period of 12.0 h , assuming the cell is 87.0 % efficient?

Answer 1

the electrolysis expression is:

Ni2+ + 2e- ------> Ni

1 mol of Ni requires 2 mol of electron

1 mol of electron = 96485 C

So,1 mol of Ni requires 192970 C

let us calculate the charge passed:

t = 12.0 hr = 12.0*3600 s = 43200 s

time, t = 43200s

Q = I*t

= 67A * 43200s

= 2894400 C

mol of Ni plated = 2894400/192970 = 14.99922 mol

Molar mass of Ni = 58.69 g/mol

mass of Ni = number of mol * molar mass

= 14.99922 * 58.69

= 880.3 g

This is mass formed assuming it is 100 % efficient

Now use:

efficiency = actual mass * 100 / theoretical mass

87.0 = actual mass * 100 / 880.3

actual mass = 766 g

Answer = 766 g