1:21 PM ooooo Verizon session masteringchemistry.com Exercise 20.127 Mastering C

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1:21 PM ooooo Verizon session masteringchemistry.com Exercise 20.127 Mastering Chemistry 13 of 16 Exercise 20.127 A thin layer of gold can be applied to another material by an electrolytic process. The surface area of an object to be gold plated is 49.9cm and the density of gold is 19.3 g/cm A current of 3.20 A is applied to a solution that contains gold in the +3 oxidation state. Part A Calculate the time required to deposit an even layer of gold I.00x 10-3cm thick on the object. Give Up Submit Continue

Explanation / Answer

Q = I X t = (nFw)/M   GIven i=3.20 A

also Q = (n X Fx W)/M        n---># of electrons =3 since +3 is the oxidation state of gold (Au)

      => t=Q/I                                      F---> Faraday 96500 coloumbs,W--> wt of gold deposited

                                                          M= molecular wt of Au= 196.97g/mole

since density =mass/volume => mass = D X V =>19.3 g/Cm^3 X (49.9 cm^2 x 1.00 x 10^-3 cm)

      => mass of au = 0.96307 g

Au3+ (aq) +3e- ------> Au (s) hence n = 3 and F = 96500C

Q= (3 x 96500 x0.96307) /196.97=14154.88

since t = Q/I =14154.88/ 3.20 =4423.4sec

the answer is 4423.4 sec

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