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Chromium metal can be electroplated from an acidic solution of (CrO4)-2 a.      Write the half reaction...

Chromium metal can be electroplated from an acidic solution of (CrO4)-2

a.      Write the half reaction

b.     Determine the equivalent weight of Cr.

c.      What mass of Cr, in grams, will be deposited by a current of 98.54 C?

d.     What mass of Cr, in grams, will be deposited by a current of 3.0 amps passing for 4 minutes?

e.      How many minutes will it take for 1.5 grams of Cr to be deposited by a current of 1.2 amps?

f.      How many Faradays of electricity are required to deposit 52 grams of Cr.?

Solutions

Expert Solution

CrO4^-2 oxidation state of Cr = +6

CrO4-2 + 8H+ + 6e- -----------------------> Cr (s) + 4H2O

(a) half -reaction :

CrO4-2 + 8H+ + 6e- -----------------------> Cr (s) + 4H2O

(b) equivalent weight = molar mass / 6

                                    = 51.996 /6

                                     = 8.666 g

(c)

    What mass of Cr, in grams, will be deposited by a current of 98.54 C?

q = 98.54 C

Faraday law

W = E x i x t / F

     = E x q / F

W = 8.666 x 98.54 / 96500

W = 0.0088g

mass of Cr = 0.0088g

(d)

   What mass of Cr, in grams, will be deposited by a current of 3.0 amps passing for 4 minutes

W = E x i x t / 96500

      = 8.666 x 3 x 4 x 60 / 96500

       = 0.0647 g

weight of Cr = 0.0647 g

e.) How many minutes will it take for 1.5 grams of Cr to be deposited by a current of 1.2 amps?

W = E x i x t / 96500

1.5 = 8.666 x 1.2 x t / 96500

t = 13919.339 seconds

t = 232 minutes

f. ) How many Faradays of electricity are required to deposit 52 grams of Cr.

6 Faradays   are needed

queen_honey_blossom answered 1 year ago
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