Question

A current of 5.66 A is passed through a Cr(NO3)2 solution for 1.20 hours. How much chromium is plated out of the solution?

____g

Answer 1

the electrolysis expression is:

Cr2+ + 2e- ------> Cr

1 mol of Cr requires 2 mol of electron

1 mol of electron = 96485 C

So,1 mol of Cr requires 192970 C

let us calculate the charge passed:

t = 1.2 hr = 1.2*3600 s = 4320 s

time, t = 4320s

Q = I*t

= 5.66A * 4320s

= 24451.2 C

mol of Cr plated = 24451.2/192970 = 0.12671 mol

Molar mass of Cr = 52 g/mol

mass of Cr = number of mol * molar mass

= 0.12671 * 52

= 6.59 g

Answer = 6.59 g