The degree of dissociation (α) is defined as the fraction of electrolyte molecules that dissociate into ions, calculated using the formula α = (Kd/C)^(0.5), where Kd is the dissociation constant and C is the total concentration of the electrolyte in mol/L. The discussion clarifies that Kd is considered unit-less, while C has units of mol/L. Therefore, α is dimensionless and represents a percentage of dissociation. This understanding is crucial for accurately interpreting electrochemical reactions and their measurements.
PREREQUISITESChemistry students, electrochemists, and researchers involved in studying electrolyte behavior and dissociation in solutions.
Nader AbdlGhani said:What's the unit used to measure α ? if α=(Kd/C)0.5 where Kd is the dissociation constant and C is the total concentration of electrolyte .
I've already done that , but before I did so , my teacher had told me it's unit-less , he said that according to our school textbook , according to this idea , concentration is measured in mol/Litre and Kd doesn't have a unit as it's a ratio between two constants , therefore the unit of measuring alpha should be Litre/mol ,which sounds a little bit weirdBorek said:Why don't you plug units into the formula and see what you get? What is the unit of the concentration? What is the unit of Kd?
Nader AbdlGhani said:Kd doesn't have a unit
I'm sorry but what formula you want me to write ? and what do you mean the formula for alpha looks odd ? thanks .Borek said:Sure it does. Please write the formula.
Besides, I just realized your formula for α looks odd.
If ##\mathbf{AB \leftrightarrow A^+ + B^-}## then ##\mathbf{K_d=\frac{[A^+][B^-]}{[AB]}}##Borek said:Write the formula for Kd, to see what are Kd units.
α is just the dissociation percentage (fraction), I don't see how it can be calculated using formula you gave in the opening post.