Hard chrome plating is achieved by plating chromium atoms onto a metal surface s
ID: 868540 • Letter: H
Question
Hard chrome plating is achieved by plating chromium atoms onto a metal surface such as steel. The hard chrome protects the steel from rust, and it is much harder than the steel making it wear longer especially for moving parts. The pertinent reduction reaction for hard chrome plating is as follows. Cr6+(aq) + 6e- Cr(s) The oxidation is done through a nonsoluble electrode, so the balanced redox reaction uses 6 electrons. You want to plate a piece of steel that has a surface area of 1 ft^2 = 0.093 m^2. You want the thickness of the chromium layer to be 500 mu m. The density of chromium is 7.14 g/cm^3 If the current is 50 amps, how long would the electrolysis need to be run to create the desired thickness of the hard chrome coating?Explanation / Answer
Answer: Hence we know that Faraday's first law :
W = Z Q
here w is mass deposited , Z is equivalet constant = E/96500 ( here E is equivalent mass = molecular mass/valency factor) , and Q is charge = I T [here I is current and T is time in sec.]
Now according to question we have given the surface area and also the thickness
Hence the volume = surface area * thickness
volume = 0.093 * 500 * 10-6 m3 [ hence to convert micrometer in meter we have to multiply by 10-6]
volume = 4.65 * 10-5 m3 = 46.5 cm
And now in question we have given the density
so we know that density = mass / volume
mass = density * volume = 7.14 * 46.5 = 332.01 gram
hence the mass deposied [W] is equal to = 332.01 gram
and also the molecular mass of Cr = 52 g
now using W = Z Q
W = m.m * I * T /96500 * Valency factor { In the given equation valency factor = 6]
now putting all thevalues and calculate for T we get
332.01 = 52 * 50 * T / 96500 * 6
T = 73936.073 seconds means ,
T = 20.5378 hours
Hence the required answer is 20.5378 h
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