Electrolysis
Electrolysis involves passing an electric current through either a moltensalt or an ionic solution. The ions are "forced" to undergo eitheroxidation (at the anode) or reduction (at the cathode). Most electrolysisproblems are really stoichiometry problems with the addition of an amountof electric current. The quantities of substances produced or consumedby the electrolysis process is dependent upon the following:
- electric current measured in amperes or amps
- time measured in seconds
- the number of electrons required to produce or consume 1 mole of the substance
- Amps, time, Coulombs, Faradays, and moles of electrons
- Calculating the quantity of substance producedor consumed
- Calculating the time required
- Calculating the current required
Amps, Time, Coulombs,Faradays, and Moles of ElectronsThree equations relate these quantities:
- amperes x time = Coulombs
- 96,485 coulombs = 1 Faraday
- 1 Faraday = 1 mole of electrons
The thought process for interconverting between amperes and moles of electronsis:
amps & timeCoulombsFaradaysmoles of electrons
Use of these equations are illustrated in the following sections.
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Calculatingthe Quantity of Substance Produced or Consumed
To determine the quantity of substance either produced or consumed duringelectrolysis given the time a known current flowed::
- Write the balanced half-reactions involved.
- Calculate the number of moles of electrons that were transferred.
- Calculate the number of moles of substance that was produced/consumed atthe electrode.
- Convert the moles of substance to desired units of measure.
Example: A 40.0 amp current flowed through molten iron(III)chloride for 10.0 hours (36,000 s). Determine the mass of iron andthe volume of chlorine gas (measured at 25
oC and 1 atm) thatis produced during this time.
- Write the half-reactions that take place at the anode and at the cathode.
anode (oxidation): 2 Cl-Cl2(g)+ 2 e-cathode (reduction) Fe3+ + 3 e- Fe(s)
- Calculate the number of moles of electrons.
- Calculate the moles of iron and of chlorine produced using the number ofmoles of electrons calculated and the stoichiometries from the balancedhalf-reactions. According to the equations, three moles of electronsproduce one mole of iron and 2 moles of electrons produce 1 mole of chlorinegas.
- Calculate the mass of iron using the molar mass and calculate the volumeof chlorine gas using the ideal gas law (PV = nRT).
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Calculatingthe Time Required
To determine the quantity of time required to produce a known quantityof a substance given the amount of current that flowed:
- Find the quantity of substance produced/consumed in moles.
- Write the balanced half-reaction involved.
- Calculate the number of moles of electrons required.
- Convert the moles of electrons into coulombs.
- Calculate the time required.
Example: How long must a 20.0 amp current flow through a solutionof ZnSO
4 in order to produce 25.00 g of Zn metal.
- Convert the mass of Zn produced into moles using the molar mass of Zn.
- Write the half-reaction for the production of Zn at the cathode.
Zn2+(aq) + 2 e-Zn(s)
- Calculate the moles of e- required to produce the moles of Znusing the stoichiometry of the balanced half-reaction. Accordingto the equation 2 moles of electrons will produce one mole of zinc.
- Convert the moles of electrons into coulombs of charge using Faraday'sconstant.
- Calculate the time using the current and the coulombs of charge.
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Calculatingthe Current Required
To determine the amount of current necessary to produce a known quantityof substance in a given amount of time:
- Find the quantity of substance produced/or consumed in moles.
- Write the equation for the half-reaction taking place.
- Calculate the number of moles of electrons required.
- Convert the moles of electrons into coulombs of charge.
- Calculate the current required.
Example: What current is required to produce 400.0 L of hydrogengas, measured at STP, from the electrolysis of water in 1 hour (3600 s)?
- Calculate the number of moles of H2. (Remember, at STP, 1 moleof any gas occupies 22.4 L.)
- Write the equation for the half-reaction that takes place.
Hydrogen is produced during the reduction of water at the cathode.The equation for this half-reaction is:
4 e- + 4 H2O(l)2 H2(g) + 4OH-(aq)
- Calculate the number of moles of electrons. According to the stoichiometryof the equation, 4 mole of e- are required to produce 2 molesof hydrogen gas, or 2 moles of e-'s for every one mole of hydrogengas.
- Convert the moles of electrons into coulombs of charge.
- Calculate the current required.
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FAQs
Yes. Unlike other hair removal methods that offer a temporary solution, Electrolysis is permanent and is the only FDA approved method of permanent hair removal.
What is the electrolysis process? ›
electrolysis, process by which electric current is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction).
What is a downside to electrolysis? ›
Electrolysis Cons
It's a time-consuming procedure requiring multiple sessions. Skin discoloration is a possibility. The electricity in the device can actually destroy the capillaries in the surrounding areas. It can be very painful. It is not recommended for people with rosacea since the skin is so easily irritated.
How painful is electrolysis? ›
You'll feel a sharp sting or temporary warmth as each hair follicle is treated. How much the process hurts depends on how you react to pain and the area being treated.
Is electrolysis cheaper than laser? ›
Costs. Electrolysis is cheaper on a per session basis, but because the number of treatments is greater, the costs tend to even out. While paying less per session may appeal to many, most laser treatment centers offer financing, so cost tends to be a non-factor.
Why is electrolysis hair removal so expensive? ›
Electrolysis tends to be more expensive than laser hair removal because it requires more sessions to see full results. And treating larger areas of the body with electrolysis will add up quickly.
How many sessions of electrolysis do you need? ›
“On average, between 10 and 14 treatments are needed for extensive electrolysis in a particular area,” says Green. Each electrolysis session is typically done every four to six weeks. Therefore, the completion of electrolysis treatments can take a minimum of one year.
Is electrolysis covered by insurance? ›
One common question that often arises is whether electrolysis hair removal is covered by insurance. In general, health insurance companies will not reimburse for electrolysis treatments under any circ*mstances, as excessive hair growth is considered a cosmetic problem.
Why is electrolysis not popular? ›
Electrolysis is not as popular as laser hair removal for a few reasons: Longer Treatment Time: As mentioned, treating each hair follicle one by one makes electrolysis a much lengthier process. Discomfort: The procedure can be more uncomfortable, which deters some people from opting for it.
Who should avoid electrolysis? ›
Absolute Contra-Indications – Requires a Doctor's Note: Diabetes, heart condition, hemophilia, pacemaker, seizures, transplant, surgery.
Electrolysis is very safe. Very slight risks of infection (from an unsterile needle) or scarring exist if the electrolysis is not done correctly. These risks are very low if you choose a certified, professional electrolysis practice. You may have a slight reddening of the skin during or right after treatment.
Do you shave for electrolysis? ›
Please don't shave the area prior to your appointment
We're often asked if you need to shave or trim your hair before electrolysis (as you might before a laser treatment). The answer is no – in fact, as you'll read in the next tip, we ask that you don't shave the area at least 3 days before your treatment.
What does your face look like after electrolysis? ›
After treatment, your skin may be red, swollen (inflamed), and tender. These are temporary side effects. Redness and swelling should disappear in a few days.
How much hair can electrolysis remove in an hour? ›
Your electrologist removes individual hairs from the body one by one, approximately 200-800 hairs per hour. Laser covers large areas and can treat thousands of hairs.
Can hair grow back after electrolysis? ›
The Greek translation of electrolysis is "to break up by electricity." So electrolysis procedure works by destroying the roots and the follicle of unwanted hairs with an electric current. The end result is that the unwanted hairs do not grow back.
How many electrolysis sessions are needed for permanent hair removal? ›
You'll also need to factor in the thickness and density of the hair. The more hair follicles, the more sessions you'll need to remove them. In addition, most hair follicles will need to be targeted at least twice to have a permanent effect. Expect to go through around eight to twelve sessions for a permanent result.
Is electrolysis completely permanent? ›
Unlike other hair removal options, professionally performed electrolysis eliminates unwanted hair, permanently, with unsurpassed results. Moreover, it does so for the largest variety of skin and hair types. Waxing, threading and tweezing are alike. With all of these, ingrown hairs and discoloration may result.
Does electrolysis ever end? ›
Remember, this is a permanent treatment so while it may seem lengthy at first at least there is an end in sight.
Coulombs
Cl2(g)+ 2 e-
