Electroplating - Online Tutor, Practice Problems & Exam Prep

Electroplating involves using an electrical current to deposit metal cations onto an electrode. The electrical current, measured in amperes (A), is the flow of electrons between electrodes at a rate of one coulomb per second. Electrochemical stoichiometry calculations in electrochemical cells require converting the given time to seconds, using the current to find the charge, and then applying Faraday's constant (96,485 coulombs per mole of electrons) to determine moles of electrons. A mole-to-electron comparison using balanced chemical equation coefficients allows conversion to moles of the plated element. From there, moles can be converted into various units such as grams or molecules. When starting with mass, the process involves going from grams to moles using atomic mass, then to moles of electrons, charge, and finally, using the current to find the time for the electroplating process.

Electrical Current (A)

Now electroplating is the use of electrical current to coat metal cations onto a metal electrode. Now here when we say electrical current, this is the rate at which electrons move from electrode to electrode in a closed complete circuit. So we're talking about electrons traveling from the anode to the cathode.

Now here remember when we say rate, rate is just amount of something over changing time. Now here the SI unit for electrical current is amperes or amps, which uses capital A. And what's important here is that one ampere is equal to 1 C/s. So this is going to be an important conversion factor when we're talking about the calculations involved with typical electroplating questions.

Electroplating Example

Here it says determine the electrical current produced if a charge of 4.14 * 10 to the three coulomb passes through a wire for 15 minutes. All right, so remember electrical current is in amps, and remember that one amp is equal to 1 coulomb per second. So what we need to do here is we need to find units of coulombs and units of seconds, combine them together to find our amps which is equal to our current.

Alright, so here we already have the Coulomb's which is 4.14×103 C. All we have to do at this point is figure out from 15 minutes how many seconds do we have. So we have 15 minutes. Remember, one minute is equal to 60 seconds. Minutes cancel out here and we're going to have 900 seconds.

Take those 900 seconds, plug it here on the bottom. So that's going to give me 4.6 C/s or 4.6 amps. This would be our electrical current.

Electrochemical Stoichiometry

Now electrochemical stoichiometry deals with calculations in a metrochemical cells that involve current and charge. Now we're going to say this version is used when the given amount is in units of time, so hours, days, seconds, what have you. Now here they're going to give you units of time. So we start out with seconds of given. So if they give it to you in any other type of units of time, you have to convert them to seconds.

Once you have seconds of given, we'll utilize current with this. Remember current is the same thing as amperes which is Coulomb's per second. We would utilize seconds with current and that will help us isolate charge. So we have charge of given charge. Here we just use Coulombs as its units. From this point we interact with Faraday's constant. Remember Faraday's constant is 96,045 coulombs per moles of electrons. Interacting with this would then give us moles of electrons given.

At this point we need to go for moles of electrons and we need to make a jump to an area where we don't know as much. We're going to go to an area of unknown. This kind of a leap of faith. This jump will take us from moles of electrons to moles of unknown. Now here when we make this jump we actually have to do a mole to electron comparison. In this step we have to use the coefficients in the balance equation. So for example, one mole of your particular element has a transferring of three moles of electrons. So it would be 1 mole of element per three moles of electrons. This is the mole to electron comparison you'd have to do.

And then at this point, if you know the moles of your substance, we all know how to do different types of conversions. You can change those moles into grams, you could change them into molecules, you could change them into ions, you could change them into kilograms. But this is the setup that you utilize when they're giving you in the beginning units of time.

Electroplating Example

Here we're told that gold can be plated out of a solution containing gold 3 ion based on the following half reaction. Half reaction here is that says that for every one mole of gold 3 ion we absorb 3 moles of electrons to give us one mole of gold solid. Now here it says what mass of gold is plated by a 41 minute flow of 6.8 amps in terms of current.

Now here they're giving us units of time. In the beginning it's up to us first to change these minutes of giving into seconds of giving. So we're going to start out by saying we have 41 minutes. We need to convert it into seconds of given for everyone minute. It's 60 seconds right? Now that we have seconds, we're going to introduce current. Now remember current or AMS SO1 amp is equal to 1 coulomb per one second. So when I give me 6.8 amps here, it's equal to 6.8 coulombs per one second.

We want seconds to cancel slots, so we're going to put the one seconds on the bottom, 6.8 Coulomb's on the top. Now that we have Coulombs, we're going to have to go from seconds of given to charging given, and that's what we just did here. Next, we're going to go from charge a given to moles of electrons of given by utilizing Faraday's constant 96,045 coulombs per one mole of electrons.

Now that we have moles of electrons given, we're going to make the jump to moles of unknown. So we have to look at the coefficients in the balance equation and it is for everyone mole of my solid. I have 3 moles of electrons, so it's 3 moles of electrons for every one mole of gold. So moles of electrons can't slap. Now I have moles of gold here. We want mass, so we're going to end at grand.

So last thing is we're going to say for everyone mole of gold. According to my periodic table, we're going to say the atomic mass of gold is 196.967g of gold. So here, when we work this out, we're going to get 11.383 grams of gold. If we want to do it in terms of sick figs, this has two sig figs. This has two sig figs. So you can round to just 11 grams of gold. So here this will be our final answer.

Stoichiometric Chart and time.

Here we're going to say when the initial mass for half reaction is given, we can utilize the mass version of the stoichiometric chart to find time. So here we're going to say this version is used when the given amount is in units of mass.

Here we're going to start out with grams of given and with these grams are given. We know how to go from grams to moles. We use the atomic mass of the oven. Now we're going from moles of Gibbon to moles of electrons. Given this requires us to do a jump when we do this jump, in actuality what we're doing is a mole of your element to moles of electrons transferred. So it's a mole to electrons comparison.

Here we'd have to use the coefficients in the balance equation. Now once we know the moles of electrons, we can utilize Faraday's constant and this will help us find the charge of our unknown. And once you know the charge of your unknown, you can use current which will then help you find seconds of unknown. So this is the chart we utilize when given our mass initially.

Electroplating Example

How much time in hours would it take to play out 42.1 grams of nickel using a current of 3.08 amps. So here we have one mole of nickel 2 plus ion reacting with two moles of electrons to give us one mole of nickel solid. Here we're going to start out with grams of given 42.1 grams of nickel, and we're going to change those grams of giving it to moles of given grams go on the bottom so they can cancel out. One mole of nickel goes on top here.

If we look at the periodic table, we'll find the atomic mass of nickel that comes out to 58.693. We now have moles of given. So next step is to get moles of electrons of given. To do that, we look at the coefficients in the balanced equation. Wherever one mole of nickel solid, there's two moles of electrons involved. So for every one mole of nickel, there's two moles of electrons. So moles of nickel are gone.

Now we need to go from moles of electrons of given to charge of unknown. We do this by utilizing faradays constant. So for every one mole of electrons it's 96,045 coulomb's. Now that we have charge of unknown we can find here. Let's see from this we can utilize our current and that'll help me find seconds involved. Remember amps is equal to 3.08 here coulombs per second. So we put the 3.08 coulombs on the bottom, one second on the top.

We have seconds now. So now it just becomes converting seconds into minutes and then into hours. So we're going to say we have 60 seconds for everyone minute we have here. One hour is equal to 60 minutes. Everything here cancels out, so at the end we're going to get 12.483 hours. Here are numbers in the question. Have three sig figs so I'm going to round this to 12.5 hours O this would be our final answer.

Cu²⁺ is reduced to Cu(s) at an electrode. If a current of 1.25 A is passed for 72 hours, what mass of copper is deposited at the electrode? (MW of Cu: 63.55 g/mol)

• A. 91.5 g
• B. 55.8 g
• C. 83.1 g
• D. 110 g

A solution of Mn⁺⁵ is used to plate out Mn in an electrochemical cell. If a total of 1.13 g of Mn is plated out in a total time of 1600 seconds, what was the electrical current used? (MW of Mn is 54.94 g/mol)

• A. 3.5 A
• B. 6.2 A
• C. 1,8 A
• D. 7.7 A

Here’s what students ask on this topic:

What is electroplating?

Electroplating is a process used to coat the surface of an object with a thin layer of metal through an electrochemical reaction. Essentially, it involves submerging the object you want to plate, known as the substrate, into a solution containing the plating metal, such as gold, silver, or copper. This solution is known as an electrolyte.

The object to be plated is connected to the negative terminal of a power supply, becoming the cathode. A piece of the plating metal is connected to the positive terminal, becoming the anode. When electricity is applied, the metal ions from the electrolyte solution are attracted to the negatively charged substrate. They deposit onto the surface, forming a new metal coating.

Electroplating is used for various purposes, including corrosion resistance, aesthetic enhancement, increasing surface hardness, and improving electrical conductivity. It's a common technique in manufacturing, jewelry making, and electronics.

How does electroplating work?

Electroplating is a process that uses electrical current to coat an electrically conductive object with a thin layer of metal. Here's a simplified explanation of how it works:

1. Preparation: The object to be plated, known as the substrate, is thoroughly cleaned to remove any dirt, grease, or oxides that might interfere with the plating process.
2. Setup: The substrate is then placed into an electrolyte solution, which contains the metal ions of the metal you want to plate with. The substrate acts as the cathode (negative electrode), and an anode (positive electrode) made of the plating metal is also placed in the solution.
3. Electroplating: When an electrical current is applied, the metal ions in the solution are attracted to the negatively charged substrate. They gain electrons (reduction) and deposit onto the substrate's surface as a thin layer.
4. Result: The thickness of the metal coating can be controlled by adjusting the time the substrate is left in the solution and the intensity of the electrical current.

Through electroplating, objects can be coated for various purposes, including corrosion resistance, aesthetic appeal, increased strength, or to improve electrical conductivity.

What is electroplating?

Electroplating is a process that uses electrical current to coat an electrically conductive object with a thin layer of metal. This is achieved by immersing the object to be plated, known as the substrate, along with a piece of the metal to be deposited, into an electrolyte solution. The substrate acts as the cathode (negative electrode), and the metal acts as the anode (positive electrode).

When an electrical current is applied, positively charged metal ions in the solution are attracted to the negatively charged substrate. These ions undergo a reduction reaction, changing from their ionic state to a solid state, and deposit onto the surface of the substrate, creating a new layer of metal. This process can be used for various purposes, such as improving corrosion resistance, enhancing appearance, increasing thickness, or to impart desired surface properties to the substrate.

What is electroplating used for?

Electroplating is a process used to coat the surface of a metal or other conductive material with a thin layer of another metal. This is achieved by using an electrical current to reduce dissolved metal cations so that they form a coherent metal coating on an electrode. The primary purposes of electroplating are to improve a material's properties, such as corrosion resistance, abrasion resistance, aesthetic qualities, and electrical conductivity. For example, chrome plating is often used for its shiny, reflective finish and rust resistance, while gold plating is used in electronics for its excellent conductivity and resistance to corrosion. Additionally, electroplating can be used to build up thickness on undersized parts, create uniformity in surface texture, or to coat objects for decorative purposes.