quick revision question (1 Viewer)

[xeriphic]

i came by this and was just wondering, in the equailibrium reaction of carbon dioxide and carbonic acid, if I pump in more carbon dioxide, would that be regarded as increase in pressure or concentration o.0 I'm just curious

 

[Xayma]

Does it matter? Both have the same result (more CO₂ dissolving).

A more difficult one (at HSC level) would be pumping in more NH₃ in a N₂+3H₂ <------> 2NH₃ reaction, which effect would dominate? Im thinking it would go to the left more purely because in normal conditions it lies strongly to the left but IM not sure.

 

[Premus]

if u put in more carbon-di oxide , i think it can be regarded as increasing the concentration of CO2.

If u increase the pressure, i think u actually decrease the volume of the reaction vessel.

 

[xeriphic]

indeed it doesn't matter in terms of the result, but I needed to explain it as with concentration or with pressure, that's when the problem comes in, as for the NH3 question, I would say to the left too from the principle, okai thanks both for helping out

 

[CM_Tutor]

Xeriphic, you should discuss the addition of carbon dioxide as a change in concentration, and NOT as a change in pressure. In this case, it doesn't really matter (as pressure is proportional to concentration), but Xayma's example illustrates the problem with the pressure analysis.

Xayma, you are correct that your system will move left, the reason being that the disturance being minimised is an increase in concnentration.

An increase in pressure need not have any effect. For example, if you added inert argon gas to the system:

N₂ (g) + 3H₂ (g) <---> 2NH₃ (g)

at equilbrium, there would be no change in the position of the system.

For a change in pressure to have any effect on an equilbrium system, it must be caused by a change in volume. Any other change that results in a change in pressure which causes the position of equilibrium to move will be due to reasons other than pressure.