Question

A Cr3+(aq) solution is electrolyzed, using a current of 7.40 A .

What mass of Cr(s) is plated out after 2.50 days?

What amperage is required to plate out 0.210 mol Cr from a Cr3+ solution in a period of 8.40 h ?

Answer 1

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 the charge passed:

t = 2.5 days = 2.5*24*3600 s = 216000 s

time, t = 216000s

Q = I*t

= 7.4A * 216000s

= 1598400 C

mol of Cr plated = 1598400/289455 = 5.5221 mol

Molar mass of Cr = 52 g/mol

mass of Cr = number of mol * molar mass

= 5.5221 * 52

= 287 g

Answer = 287 g

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