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Urgent: Equilibrium bits and pieces (1 Viewer)

Aerlinn

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An urgent question, but when you're talking about the effects of temperature on an equilibrium, any, say, H3PO4(aq) <---> H2PO4-(aq) + H+(aq) (exothermic), is it wiser to talk about it in terms of the increasing and decreasing of K values, or the shifting of the equilibrium position? Eg. If you were asked about what increasing temperature would do to the above, would you say K decreases, or would you say, equilibrium shifts to the left to produce greater concentrations/amounts of H3PO4?
As far as I know, they are two different things, because equlibrium position can change all it wants with the K value staying the same if temp doesn't change. My textbook doesn't talk about these questions in terms of K changing, it talks about equilibrium position which is strange... How should approach these questions?
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With concentration-time graphs, where the concentration of each species in an equilibrium mixture's plotted over the course of the reaction, what happens when you get an equilibrium like SO2(g) + O2(g) <---> 2SO3(g)... and you decrease the volume (thus increase concentration)? The concentrations of SO2(g), O2(g), and SO3(g) would all increase dramatically (vertical line), then what would happen after that? There's the same number of particles on each side, so there's not really a net forward/reversereaction. What would the graph look like?

Also when you change the temp of a system at equilibrium, I know you'd get a slope in each of the species in the mixture till they reach constant concentration again (concentration time graphs), a horizontal line, but do those slopes correspond to the mole ratios? I know with all the other changes you can make to the system, eg. volume change, adding species, etc, have slopes corresponding to the mole ratios, just not sure about temperature.
:wave:
A diagram to illustrate what I mean, see below:


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Help= :) :) :wave:
 
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xiao1985

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if you do industrial chem, you'd know that the ONLY aspect that changes K is the temperature... so yes, changing temperature changes K...

yea... it would look like a step

true... cept... shouldn't conc of SO3 decrease instead of increase?!
 

Aerlinn

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Yes, that's true. Just wondering whether it's 'more' important to mention K, or equilbrium position that's all

Heheh, ooops, SO3 should increase, you're right :)
 

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