Plastic articles can be chromium-plated by coating them with thin layer of graphite paste,placing them in a bath of aqueous chromium(III) sulphate and electroplating.
a)Suggest a reason why the article is first coated with graphite.
b)what substance could be used for the other electrode in the electroplating cell/
c)Draw a diagram of the electrical circuit for the electroplating.
d)If a current of 0.5 A were passed through the cell for 300 sec,what would be the increase in mass due to the chromium plating?
e)why is it not possible to coat articles with zinc by this method?
The plastic article must be one of the electrodes but it doesn't conduct electricity. Therefore, the graphite coasting serves that purpose.
I would think a graphite rod or carbon rod would serve as the other electrode.
amp x seconds = coulombs
0.5A x 300 s = 150 coulombs,
96,485 coulombs will deposit 52.0/3 = 17.33 g Cr.
g Cr plated = 17.33 x 150/96,485 = ? g Cr.
Graphite is an inner electrode is no involved in the reactions
a) Well, coating the article with graphite is just a fancy way of saying that it's time to get artsy. You see, when you coat the plastic article with graphite, it's like giving it a little black dress. It's all about fashion, darling! But seriously, the purpose of the graphite is to provide a conductive surface that allows for the electroplating process to occur smoothly.
b) Now, let's talk about the other electrode in the electroplating cell. You know, the one that brings the spark to the party. Well, my friend, in this case, we would typically use a metal electrode, like titanium or stainless steel. It's like having a charismatic dance partner to create a magical electroplating routine. They make a great team!
c) Ah, the electrical circuit for electroplating. Picture this: a circle of electrical fun! You've got your power source, like a battery, connected to the graphite-coated plastic article (the anode) and the metal electrode (the cathode) in the electroplating bath. It's like a little party where the current flows from the anode to the cathode, making the magic of electroplating happen. And don't forget those trusty wires connecting everything together in a lovely circle. Voilà, your very own electroplating circuit!
d) Now, let's calculate the increase in mass due to the chromium plating. If a current of 0.5 A is passed through the cell for 300 seconds, we take that current and multiply it by the time (0.5 A * 300 seconds = 150 Coulombs). Then, we need to convert Coulombs to grams using some high-level math (well, maybe not that high). The increase in mass will depend on the charge-to-mass ratio, which is specific to the metal being electroplated. Without that information, my calculations will remain as elusive as my missing sock.
e) Oh, zinc, how you complicate things! Unfortunately, my dear friend, zinc cannot be coated using this method. You see, zinc is just too finicky to play well with graphite and the electroplating bath. It prefers other methods, like hot-dip galvanizing or zinc spraying. Maybe it's just camera shy and doesn't want to be electroplated. Who can blame it? We all have our moments!
a) The article is first coated with graphite because graphite is a good conductor of electricity. It allows for the flow of electrical current during the electroplating process.
b) The other electrode in the electroplating cell could be made of chromium or any other material that can serve as a source of chromium ions for deposition.
c) Here is a diagram of the electrical circuit for the electroplating:
[Power Source (+) terminal] --- [Anode (+)] --- [Electroplating Bath] --- [Cathode (-)] --- [Power Source (-) terminal]
d) To calculate the increase in mass due to chromium plating, we need to know the Faraday's constant and the molar mass of chromium. Using Faraday's law of electrolysis, the equation is:
Mass (g) = (Current (A) * Time (s) * Molar Mass (g/mol)) / (Faraday's Constant (C/mol))
e) It is not possible to coat articles with zinc by this method because zinc requires a different electroplating bath and conditions. Zinc electroplating typically involves a bath of zinc sulfate or zinc chloride solution and a separate zinc anode. Chromium electroplating, on the other hand, uses a bath of chromium(III) sulfate and a chromium anode. The specific chemistry and electroplating conditions are different for each metal.
a) The article is first coated with graphite because graphite is a good conductor of electricity. It acts as a barrier between the plastic article and the electroplating bath, ensuring a uniform and smooth flow of electricity during the electroplating process.
b) The other electrode in the electroplating cell can be made of a material that is compatible with the electroplating bath and can act as a source of the metal ions to be plated. In this case, it could be a metal plate or rod made of chromium or a similar material.
c) Here is a diagram of the electrical circuit for the electroplating process:
Graphite-coated plastic article (cathode) —— Electroplating bath (containing chromium(III) sulphate) —— Chromium electrode (anode)
d) To calculate the increase in mass due to chromium plating, you need to know the Faraday's constant, which represents the charge required to deposit one mole of the metal, and the molar mass of chromium. The equation that relates these values is:
Increase in mass = (Current × Time) / (Faraday's constant × Molar mass of chromium)
Plug in the given values: Current = 0.5 A, Time = 300 sec
e) It is not possible to coat articles with zinc by this method because zinc's electroplating process involves a different electrolyte compared to chromium. Zinc electroplating usually uses an electrolyte containing zinc cyanide or zinc chloride. Additionally, zinc electrodeposition requires specific electrode materials and operating conditions that are incompatible with the use of graphite-coated plastic articles.