Understanding Coulometry: A Quantitative Analytical Technique Utilizing Faraday’s Laws of Electrolysis

Define coulometry and give the relationship between the experimentally measurable variables: moles of substance (mol), current (l), time (t), and moles of electrons (n). Be sure to include Faraday’s constant, F, in its proper place.

Coulometry is a quantitative analytical technique used to determine the amount of substance in a sample by measuring the quantity of electricity passed through it during an electrolysis process

Coulometry is a quantitative analytical technique used to determine the amount of substance in a sample by measuring the quantity of electricity passed through it during an electrolysis process. This method relies on Faraday’s laws of electrolysis, which state that the amount of a substance produced or consumed during electrolysis is directly proportional to the amount of electricity passed through the system.

In coulometry, the experimentally measurable variables are moles of substance (mol), current (I), time (t), and moles of electrons (n). The relationship between these variables can be derived using Faraday’s constant, denoted as F, which is defined as the charge of one mole of electrons.

The relationship can be expressed using Faraday’s laws:

1. Faraday’s First Law: The amount of a substance produced or consumed during electrolysis is directly proportional to the amount of electric charge passed through it.

Mathematically, this is represented as:
m = nF

Where:
m = moles of substance produced or consumed
n = moles of electrons transferred (also known as stoichiometric coefficient)
F = Faraday’s constant (approximately 96,485 C/mol)

2. Faraday’s Second Law: The quantity of electric current passing through a substance is directly proportional to the amount of substance produced or consumed.

Mathematically, this is represented as:
I = nF / t

Where:
I = current (in amperes)
n = moles of electrons transferred
F = Faraday’s constant
t = time (in seconds)

Combining both Faraday’s laws, we can relate the moles of substance (m), current (I), time (t), and moles of electrons (n) as follows:

m = (I * t) / F

This equation allows us to calculate the moles of substance produced or consumed in a coulometric experiment, given the current and time. Conversely, by measuring the moles of substance and the current, we can determine the time required for the electrolysis process.

It is important to note that the Faraday’s constant (F) is a fundamental physical constant and represents the charge of one mole of electrons, which is approximately equal to 96,485 C/mol.

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