K with relation to change in pressure/volume/temperature

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martha-1I
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Joined: Fri Sep 26, 2014 2:02 pm

K with relation to change in pressure/volume/temperature

Postby martha-1I » Sat Nov 22, 2014 12:31 am

Why is it that K does not change when there is a change in pressure or volume, but does change when there is a change in temperature?
I know that when the concentration of reactants and products does not change the reaction has reached equilibrium and that K is the relationship between the concentration of reactants and products. Does this mean that when there is a change in pressure or volume, the reaction remains at equilibrium and when there is a change in temperature, the reaction shifts from equilibrium?

Chem_Mod
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Re: K with relation to change in pressure/volume/temperature

Postby Chem_Mod » Sat Nov 22, 2014 5:40 pm

A reaction will temporary be out of equilibrium while a reactant or product is added, and when it comes back to equilibrium it will have the same value for K that it had before the reactant or product was added.

Anything that changes the concentration of any species will be the same as above.
For a gas phase reaction changing the volume is changing the concentration of reactants and products, and if the moles of reactants and products in the balanced equation are not the same then the reaction will not be at equilibrium when the volume change occurs.

Temperature permanently changes the value of K. See my Friday class lecture (Nov 21, 2014) and demo. Students at the end of my lecture 4 said my lecture was particularly clear and the demo helpful.

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

Re: K with relation to change in pressure/volume/temperature

Postby martha-1I » Sun Nov 23, 2014 11:16 am

Yes the demo did help me visualize it, but I was still a bit confused after it. Thanks for the clarification here!


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