Question

How many minutes will it take to plate out 2.19 g of chromium metal from a solution of Cr³⁺ using a current of 35.2 amps in an electrolyte cell?

Answer 1

the electrolysis expression is:

Cr3+ + 3e- ------> Cr

1 mol of Cr requires 3 mol of electron

1 mol of electron = 96485 C

So,1 mol of Cr requires 289455 C

let us calculate mol of element deposited:

we have below equation to be used:

number of mol, n = mass/molar mass

= 2.19/52

= 0.04212 mol

total charge = mol of element deposited * charge required for 1 mol

= 0.04212*289455

= 12190.5087 C

we have below equation to be used:

time = Q/i

= 12190.5087/35.2

= 346.3213 seconds

= 346.3213/60 min

= 5.77 min

Answer: 5.77 min