Question

What mass of Ni2+ is produced in solution by passing a current of 67.0 A for a period of 14.0 h , assuming the cell is 87.0 % efficient?

Answer 1

Electrolysis equation 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 = 14.0 hr = 14.0*3600 s = 5.04*10^4 s

time, t = 5.04*10^4s

Q = I*t

= 67A * 5.04*10^4s

= 3.377*10^6 C

mol of Ni plated = 3.377*10^6/192970 = 17.5 mol

Molar mass of Ni = 58.69 g/mol

mass of Ni = number of mol * molar mass

= 17.5 * 58.69

= 1.027*10^3 g

This is theoretical mass

Now use:

% yield = actual mass * 100 / theoretical mass

87.0 = actual mass * 100 / 1.027*10^3 g

actual mass = 893 g

Answer: 893 g