What's the diff btw ?changing equilibrium position and changing equil. constant?

[thebillsfan]

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My textbook says that A change in concentration,pressure or volume may alter the equilibrum position, that is, the relative amts of reactants and products but it does not change the value of the equilibrium constant. only a change in temperature can alter the equilibrium constant.

...What's the difference? If you add heat to an exothermic system you shift the equilibrium left so that the relative amounts of products over reactants is still the same. That's equivalent to changing the equilibrium position, but the textbook is making it seem like its a whole new thing.

 

[Chuck's Right Foot]

My textbook says that A change in concentration,pressure or volume may alter the equilibrum position, that is, the relative amts of reactants and products but it does not change the value of the equilibrium constant. only a change in temperature can alter the equilibrium constant.

...What's the difference? If you add heat to an exothermic system you shift the equilibrium left so that the relative amounts of products over reactants is still the same. That's equivalent to changing the equilibrium position, but the textbook is making it seem like its a whole new thing.

Keq is constant at a given temperature. Your Q (a value useful in comparing systems to Keq) shows if the reaction will shift left, right, or stay at Keq. Once you change the temp, you get a new Keq.

This is useful if you need to calculate concentrations given a Keq.