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Faraday Constant is the value that represents the amount or magnitude of electric charge carried by one mole of electrons. It was named after Michael Faraday and is denoted by the symbol F. And the unit used to measure the constant is Coulombs per mole (C/mol). One common use of the Faraday constant is in electrolysis calculations.
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Key Terms: Faraday constant, Electrolysis, Capacitance, Coulomb, Electric charge, Electron, magnitude, Mole, Avogadro constant
Faraday Constant Value
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The value of the Faraday constant accepted universally is:
| Faraday Constant (F) = 96485.33289 C/ mol or 6.022140857 × 1023 electrons |
Other Common Units
The value of Faraday constant in other units is:
| Value of Constant | Units |
|---|---|
| 96485 | Joule per volt gram equivalent |
| 23.061 | Kilo cal per volt gram equivalent |
| 26.801 | A. h/ mol |
Formula for Faraday Constant
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The formula that can be used to calculate faraday’s constant is:
| F = eNA |
Where e is the charge of electron = 1.60217662 × 10-19 Coulombs
NA is the Avogadro constant = 6.022141 × 1023 per mole
Faraday Constant and Faraday Unit
The faraday symbolizes the magnitude of the charge of one mole of electrons. It can be inferred that one faraday is equivalent to the faraday constant.
| 1 farad = 1 Coulomb per each volt |
This faraday is also the unit of capacitance. When Michael Faraday was carrying out the electrolysis the amount of charge F was discovered in the year 1833.
Electrolysis
| Frequently Asked Questions Ques. What is the unit of Faraday? Ans. In the International System of Units (SI), the coulomb (C) is the preferred unit of electric charge quantity. It is equivalent to one ampere-second (1 A.s) and represents approximately 6.24∗1018 electric charge carriers. To convert from coulombs to faradays, multiply by 1.04∗10−5. Ques. What is 1 faraday=? Ans. The Faraday constant, denoted by the symbol F and named after Michael Faraday, is the magnitude of electric charge per mole of electrons. It has the accepted value of 96485.34 coulombs in round figure 96500 coulombs. Ques. What is Faraday Constant Unit? Ans. The Faraday constant represents the amount of electric charge carried by one mole, or Avogadro's number, of electrons. It is an important constant in chemistry, physics, and electronics and is commonly symbolized by the italic uppercase letter F. It is expressed in coulombs per mole (C/mol). |
Faraday Constant and Faraday’s Law of Electrolysis
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During the process of Electrolysis, some amount of charge is required to deposit one mole of ions. Due to the electric conduction, the anions on the anode and the cations on the cathode always remain constant irrespective of the types of ions used.
Therefore, Faraday's law of electrolysis states that the mass of substance deposited or released is directly proportional to the electric charge passed in the process.
| m = Z. Q |
Where Q = charge in coulombs
Z = Proportionality in g/C
This Proportionality can also be expressed as the electrochemical equivalent(E). It means the mass consumed by the electrodes per unit charge
| Z = E / 96845 |
We already know that Q = I. t
Substituting the value of Z in m
| m = E. I. t / F = M. I. t / F. z |
Where M is the molar mass of substance in g/mol
- I is the current in ampere
- t is time in seconds
- F is the faraday constant
- Z is number of monovalent ions per substance
| Frequently Asked Questions on Faraday Law of Electrolysis Ques. What is Faraday's 1st and 2nd law of electrolysis? Ans. The laws state that: (1) the amount of chemical change produced by current at an electrode-electrolyte boundary is proportional to the quantity of electricity used. (2) the amounts of chemical changes produced by the same quantity of electricity in different substances are proportional to their equivalent weights. Ques. What is the formula of Faraday? Ans. Faraday Law says, m = Z ×Q or m = Z I t. When one coulomb corresponds to one electrochemical equivalent mass (Z) of the substance, one equivalent (or mole) of electrons flowing per second, will correspond to 96485 Equivalents mass. Ques. What is Faraday number? Ans. Faraday's constant can be derived by dividing the Avogadro constant, or the number of electrons per mole, by the number of electrons per coulomb. The former is equal to approximately 6.02 x 10 23, and the latter is approximately 6.24 x 10 18. Thus F = (6.02 x 1023) / (6.24 x 1018) |
Applications of Faraday Constant
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- It is commonly used in the process of electrolysis.
- The moles of oxidized elements can be calculated by dividing the electric charge in coulombs.
- Faraday’s Law is the mechanism behind electric generators, credit cards, metal detectors, computer hard drives, etc.
- Faraday's Laws of Electrolysis are applicable in electroplating, corrosion of metals, electrowinning, electrolytic removal of metal ions from solution, and the generation of redox species.
- A real-life application of Faraday's law is cooking using an induction hob, where a pan is heated by electrical induction, rather than via thermal conduction from a flame or electrical hotplate. Induction hobs generate heat within the pan itself, making this cooking method more efficient.
Calculation of Faraday Constant
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The accuracy of Faraday Constant is undergoing constant research to date. It was initially determined using Faraday’s Law of Electrolysis. For an electrochemical reaction, the value of current is determined to pass for a certain time. Furthermore, the value of F is calculated by measuring the amount of deposited silver.
Also Read:
| Related Articles | ||
|---|---|---|
| Electromagnetic Induction | Inductance | Lenz’s Law and Conservation of Energy |
| AC Generator | Electromagnetism | Uses of Inductor |
| Eddy Currents | Solenoid Engine | Magnetic Induction Formula |
Things to Remember
- Faraday constant is the value of electric charge carried by one mole of electrons.
- The formula that can be used to calculate the Faraday's constant is F = eNA.
- The value universally accepted is F = 96485.33289 C/ mol.
- One faraday is equal to one coulomb.
- The faraday is also the unit of capacitance.
- This faraday constant is generally used in the process of electrolysis and can be used to calculate the moles of oxidized elements.
Faraday Law Experiment
Sample Questions
Ques. What is meant by Faraday constant? (3 Marks)
Ans. Faraday’s constant is equivalent to the magnitude of electric charge carried by one mole of electrons. It is generally used in Chemistry and Physics symbolized by F. This constant was named after Michael Faraday and is denoted by the symbol F. And the unit used to measure the constant is Coulombs per mole(C/mol).
The value of faraday constant accepted universally is:
Faraday Constant(F) = 96485.33289 C/ mol or 6.022140857 × 1023 electrons
Ques. What are the applications of Faraday’s constant? (3 Marks)
Ans. Faraday's constant is generally used in Physics, Chemistry, and Electronics. Quite often it is used in the electrolysis process to calculate the moles of oxidized elements. Besides, it is also used to understand the oxygen flow rate, charge transfer, fuel cells, and enthalpy changes.
It is also used for the study of electrochemical reactions and is equal to the amount of electric charge emitted by one gram of ion from an electrolytic solution.
Ques. In Faraday's constant, F equals: (3 Marks)
(A) 96,500 C
(B) 96,500 C kg-1
(C) 96,500 kg C-1
(D) 96,500 C mol-1
Ans. Four options are given with the same magnitude of the result but with different units of results. Hence, we will apply the unit of result.
Since, 1 Faraday is the charge on NA electrons, where NA the Avogadro's number is the number of molecules in 1 gm mole of the substance, so the unit of Faraday should be coulomb /mole.
Hence only option D has such a unit. So correct answer would be D.
Ques. How long would it take to deposit 0.635 g of copper at the cathode during the electrolysis of copper(II) sulphate solution if you use a current of 0.200 amp. (4 Marks)
Ans. F = 9.65 × 104 C mol-1 (or 96500 C mol-1).
Ar of Cu = 63.5.
The electrode equation is
Cu2+ + 2e- = 2Cu
2 mol of electrons give 1 mol of copper, Cu.
Now put the numbers in. 1 mol of electrons is 1 faraday.
2 × 96500 coulombs give 63.5 g of copper.
You need to work out how many coulombs give 0.635 g of copper.
Number of coulombs = 0.635/ 63.5 × 2 × 96500 = 1930
Number of coulombs = current in amps × time in seconds
1930 = 0.200 × t
t = 1930/0.200 = 9650 seconds.
Ques. Calculate the mass of silver deposited at the cathode during the electrolysis of silver nitrate solution if you use a current of 0.10 amps for 10 minutes. (5 Marks)
Ans. F = 9.65 × 104 C mol-1 (or 96500 C mol-1 if you prefer).
Ar of Ag = 108.
The first thing to do is to work out how many coulombs of electricity flowed during the electrolysis.
Number of coulombs = current in amps × time in seconds
Number of coulombs = 0.10 × 10 × 60 = 60
Equation for the reaction at the cathode:
Ag+ + e- = Ag
1 mol of electrons gives 1 mol of silver, Ag.
Now put the numbers in. 1 mol of electrons is 1 faraday.
96500 coulombs give 108 g of silver.
So, if 96500 coulombs give 108 g of silver, all you have to do is to work out what mass of silver would be produced by 60 coulombs. Mass of silver = 60/96500 × 108 g = 0.067 g
Ques. Calculate the volume of hydrogen produced (measured at room temperature and pressure - rtp) during the electrolysis of dilute sulphuric acid if you use a current of 1.0 amp for 15 minutes. (5 Marks)
Ans. F = 9.65 × 104 C mol-1 (or 96500 C mol-1).
The molar volume of a gas at rtp = 24 dm3 mol-1.
Start by working out how many coulombs of electricity flowed during the electrolysis.
Number of coulombs = current in amps × time in seconds
Number of coulombs = 1.0 × 15 × 60 = 900
Now look at the equation for the reaction at the cathode:
2H+ + 2e- = H2
Write down the essential bits in words:
2 mol of electrons give 1 mol of hydrogen, H2.
Now put the numbers in. Two moles of electrons is 2 faradays.
2 × 96500 coulombs give 24 dm3 H2 at rtp.
So, if 2 × 96500 coulombs give 24 dm3 H2, work out what volume of hydrogen would be produced by 900 coulombs.
Volume of hydrogen = 900/(2 × 96500) × 24 dm3 = 0.11 dm3
Ques. An ammeter and a copper voltameter are connected in series through which a constant current flows. The ammeter shows 0.52 ampere. If 0.635 g of copper is deposited in one hour, what is the percentage error of the ammeter? (At. mass of copper = 63.5) (4 Marks)
Ans. The electrode reaction is:
Cu2+ + 2e- \(\rightarrow\) Cu
1 mole 2 × 96500 C
63.5 g of copper deposited by passing charge = 2 × 96500 Coulomb
0.635 g of copper deposited by passing charge
=(2×96500)/63.5×0.653 coulomb
= 2 × 965 coulomb
= 1930 coulomb
We know that Q = l × t
1930 = I × 60 × 60
I= 1930/3600=0.536 ampere
Percentage error = ((0.536-0.52))/0.536×100=2.985
Ques. How do you solve Faraday's constant? (2 Marks)
Ans. The Faraday constant is defined as F = I ∙t n.
The volume of hydrogen generated is converted to a number of moles using the ideal gas equation.
Ques. What is Z in Faraday's Law? (2 Marks)
Ans. Z is the electrochemical equivalent mass of the one-coulomb charge. One coulomb of charge corresponds to a mass of one equivalent.
Electric current and Charge (Q) Electric current is measured in ampere and it is the charges flowing per unit time (seconds).
Ques. How many Faraday of electricity is required for the reduction of 1 mole of mg2+ ions? (2 Marks)
Ans. Since to deposit 1 mol Mg, two moles of electrons are required,
Therefore, to plate one mole Mg, 2 Faradays of electricity will be required.
Ques. How many faradays are required to reduce 1 mole of bro3- to br-? (3 Marks)
Ans. 1 mol contains 6.023*1023 atoms.
The charge required to reduce 1 mol Br3+ to Br is 3*6.023*1023*1.602*10-19=3*96500 Coulombs.
We know 96500 Coulombs which is equal to 1 Faraday.
The number of Faradays required is \(\frac{3*96500}{96500} =3\;Faradays\)
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