Shifts vs Different K values

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Jessica Castellanos
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Shifts vs Different K values

Postby Jessica Castellanos » Mon Jan 20, 2020 11:52 am

When discussing the shifts in equilibrium from Le Chatelier's Principle, does this simply mean that the concentration will revert to the same K value or will it obtain a different K value?

Hiba Alnajjar_2C
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Joined: Fri Aug 09, 2019 12:17 am

Re: Shifts vs Different K values

Postby Hiba Alnajjar_2C » Mon Jan 20, 2020 12:10 pm

Changes in concentration do not result in a different K value. When we discuss the reaction shifting, this means that the concentration of either the reactants/products will change in order to minimize the effect of a change in concentration. The concentrations of the reactants and products will be different, but the ratio of products to reactants (aka the value of K) will not be. Hope this helps!

sarahforman_Dis2I
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Re: Shifts vs Different K values

Postby sarahforman_Dis2I » Mon Jan 20, 2020 12:15 pm

Jessica Castellanos wrote:When discussing the shifts in equilibrium from Le Chatelier's Principle, does this simply mean that the concentration will revert to the same K value or will it obtain a different K value?


It is important to note that the only reason that the actual value of K can change is through a change in temperature. Changing the temperature will change K. Any other change to the system (eg. change in volume or concentration) will cause the equilibrium to shift, but will not change the value of K itself. In other words, the individual concentrations will change, but the ratio of concentrations will stay constant, unless the temperature is changed.

805394719
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Re: Shifts vs Different K values

Postby 805394719 » Mon Jan 20, 2020 12:38 pm

At constant temperature, changing the concentration, pressure or volume will not change the K value. This is because the system will shift to counteract the stress and balance itself once again. For example if you decrease the amount of products, the numerator of K will go down but it will be counteracted by the reactant concentration going up which stabilizes the K value once again. Thus, the K value does not change. When temperature changes, however, K will change as well. This is because if the forward reaction is endothermic it will be favored as there is a heat input and the increase in temperature will cause it to be favored. This will cause the equilibrium concentration of the products at equilibrium to increase as the forward reaction is much more favorable than the reverse. Thus, the K value will increase. If the reaction is exothermic, the forward reaction will not be favorable and the product concentration at equilibrium will decrease, this will cause K to decrease. Temperature also causes a shift in the system but also changes the K value. A change in pressure, volume or concentration will only cause a shift but the products and the reactants will still stabilize at the same equilibrium ratio whereas this is changed when the temperature is changed.


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