Why does the equilibrium constant vary only with temperature?

[quantumlight]

why does the equilibrium constant vary only with temperature?

and why is pure substances like solids and liquids not count toward the equilibirum equation?

why do you have to have a reference pressure of 1 atm? (i know this is to take away the units but does this hav a logical function other than that? how does this affect the equation?)

can noble gases affect the equilibrium? (i think it shouldn't since the partial pressure of the original reactants would still be the same)

 

[GCT]

The policy here at PF is that you show your approach to the question before any of us are allowed to help you. However, the questions you have asked in particular are commonly asked by students outside their homework endeavors and thus I shall offer an brief explanation. An appropriate explanation for all of these questions entails several mathematical derivations and the related assumptions, all of this can be found in a standard Physical Chemistry text e.g. Physical Chemistry by Atkins.

Your text should offer a short explanation on why the equilibrium constants of some reactions in water is altered by temperature, in short, all of it stems from the relative changes in the forward and reverse rate constants for a simple reaction mechanism. Also, the rate constants are thermodynamically based, as it is associated with the activations energies for the forward and reverse reactions respectively.

Liquids and solids technically do count, to a very small degree, towards the rate equations, however they are mathematically insignificant in influencing the rate parameters.

1 atm is the standard condition.

The presence of any gas would affect the collision frequency of the analyte and thus would affect the rate dynamics.

 

[Blueshift5]

The equilibrium constant, K, is a measure of the ratio of products to reactants at equilibrium. It is a constant value at a given temperature, but can change with changes in temperature. This is because temperature affects the energy of the reactants and products, which in turn affects their rates of reaction. This can lead to a shift in the equilibrium position, resulting in a change in the equilibrium constant.

Pure substances like solids and liquids do not affect the equilibrium equation because they are not included in the equilibrium expression. This is because their concentrations do not change significantly during a reaction, and therefore do not have an impact on the equilibrium position.

The reference pressure of 1 atm is used to take away the units in the equilibrium constant expression, as you mentioned. However, it also has a logical function in that it is a standardized pressure that is commonly used in laboratory experiments. This allows for easier comparison and communication of results between different experiments.

Noble gases do not affect the equilibrium because they do not participate in the reaction. Their presence in the system does not change the partial pressures of the original reactants, as you mentioned. Therefore, they do not have an impact on the equilibrium position or the equilibrium constant.