Good observation. The equations are definitely similar. The equations describe very different things (equilibrium surface coverage vs reaction rate). But the similarity isn't entirely coincidental. Both models describe a phenomenon that starts out small (no adsorption when the pressure is zero; no reaction when the substrate is absent). The process happens proportionally to some other thing (empty surface sites or substrate). And it increases to a limiting, plateau value (full surface coverage or v_max reaction rate). So the result turns out to be similar, mathematically.
The pressure could, indeed, change over time. But in this case we're solving for the equilibrium case where the forward rate and backward rate are equal. When that is true, the pressure is constant.
First thank you a lot. Is the rate at which the degree of coverage changes due to adsorption proportional to the partial pressure p of the adsorbent A? Because we multiply the pressure
For a gas molecule to adsorb onto the surface, two things are needed: an empty site, and a molecule in the gas phase. These are like the "reactants" in the adsorption reaction. So, for an elementary reaction step, the rate is proportional to the amount of both reactants. The (1-θ)M terms is the number of empty surface sites, and the P terms is (proportional to) the number of gas molecules.
@@mimi2100 Yes, exactly. The amount of each reactant can be measured as concentration, when we are talking about solutions, or as surface coverage, when we are talking about adsorption.
these are unbeliviblely beautifull...
I'm glad you appreciate the beauty of the topic!
how is this guy ? I love him. Thank you a lot for these video series
Thank you so much, and you're welcome!
Reminds me of the Michaelis- Menten equation, is there any relation?
Good observation. The equations are definitely similar.
The equations describe very different things (equilibrium surface coverage vs reaction rate). But the similarity isn't entirely coincidental. Both models describe a phenomenon that starts out small (no adsorption when the pressure is zero; no reaction when the substrate is absent). The process happens proportionally to some other thing (empty surface sites or substrate). And it increases to a limiting, plateau value (full surface coverage or v_max reaction rate). So the result turns out to be similar, mathematically.
Is pressure not a function of time? I thought because the partial pressure of the gas should decrease as molecules bind to the surface. Am I wrong?
The pressure could, indeed, change over time. But in this case we're solving for the equilibrium case where the forward rate and backward rate are equal. When that is true, the pressure is constant.
First thank you a lot. Is the rate at which the degree of coverage changes due to adsorption proportional to the partial pressure p of the adsorbent A? Because we multiply the pressure
Yes, that's right. If there is twice as much of species A in the gas phase, it will collide with the surface twice as often, and adsorb twice as fast.
Why do you need to multiply by the pressure?
For a gas molecule to adsorb onto the surface, two things are needed: an empty site, and a molecule in the gas phase. These are like the "reactants" in the adsorption reaction. So, for an elementary reaction step, the rate is proportional to the amount of both reactants. The (1-θ)M terms is the number of empty surface sites, and the P terms is (proportional to) the number of gas molecules.
@@PhysicalChemistry So essentially, we can regard (1-θ)M term and P term as the [A] and [B] (concentration) in a chemical rate equation?
@@mimi2100 Yes, exactly. The amount of each reactant can be measured as concentration, when we are talking about solutions, or as surface coverage, when we are talking about adsorption.
Thanks a lot
You're quite welcome