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In most of the chemical laws of chemistry involving concentration of products or reactants like equilibrium constant, reaction quotient, Henry's law, Nernst equation etc, I often see a similar note stating concentration of gas to be taken as partial pressures of that gas or something similar to that. So, Why is the concentration of gases denoted in form of partial pressure ?

Does it have any relation with Dalton's law?

I don't know why this equation has been closed and it is not the duplicate of this question Please review again.

  • My guess would be that pressure is much easier to measure for a gas. Of course once you have the pressure, temperature and ideal gas equation would give you the concentration too. Also, concentration term, if replaced by partial pressure, will give you $\ce{K_p}$, not $\ce{K_c}$. Both terms are different. – TRC Jul 12 '21 at 09:36
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    Considering gas pressure is much more common than gas concentration. There is the relation for ideal gases $p=cRT$. The point is, many gas behaviour quantitatively depends rather on partial pressure than on concentration. – Poutnik Jul 12 '21 at 10:22
  • In addition to what TRC states, it can be mentioned that, in thermodynamics, concentration is not a fundamental parameter. Pressure is fundamental : it exists in the definition of the work, which is the very beginning of thermodynamics. $K_\mathrm{p}$ can be directly obtained , and has the correct dimension. On the contrary,$K_ \mathrm{c}$ is indirectly obtained, and the concentration have to be divided by a reference value of concentration – Maurice Jul 12 '21 at 10:22
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    Your question is based on a false premise that concentrations and partial pressures are interchangeable or identical entities, which is not true. Fundamentally different physical quantities cannot "take form" of one another. The question I marked as a dupe is not a literal duplicate, but it explicitly reveals this flaw and the accepted answer by Martin can be used to answer this question of yours as well. – andselisk Jul 12 '21 at 10:29
  • Are you familiar with the derivation of the equation for the equilibrium constant of an ideal gas phase reaction in terms of the standard change in Gibbs free energy? – Chet Miller Jul 13 '21 at 21:11

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