Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: acecharly on 24/10/2016 16:19:27
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If a chemical reaction takes place within a closed container and a gas is produced the pressure inside will rise as far as I know until the reaction ceases or the container breaks and releases the pressure.
My question is that if you made a container thick enough would the reaction eventually stop because there would be no further room for gas to fit or is it irrelevant and that the gas would just keep being produced creating higher and higher pressure until the reaction stopped?
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It depends on the reaction, but in general, I think the answer is: yes, a sufficiently high pressure of gaseous products will prevent a reaction from continuing.
This is best understood by thinking of chemical equilibrium. Most simple reactions are reversible, meaning that the reaction can go both forwards and backwards. A system is said to be at equilibrium when the forward and reverse reactions are taking place at the same rate, resulting in no net change of the ratio of products and reactants (so there is no net reaction, even though there are multiple opposing reactions ongoing). At a given temperature, a generic reaction of the form X --> Y + Z will have an equilibrium expression of [Y]*[Z]/[X] = K(T), where [X], [Y], and [Z] are the partial pressures of A, B, and C respectively, and K is the equilibrium constant at temperature T. The main takeaway from this is that no reversible ideal reaction can ever reach complete conversion to products in a closed system. (lots of qualifiers in there).
This is, of course, an over-simiplification. I would be happy to discuss some of the complications/exceptions/limitations if you are interested.
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Thanks for the Answer im glad it sounds oversimplified to you haha.
As pressure increases im guessing that the temperature would rise also so would the melting point of the container also come into play here?
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It really depends on a lot of factors. A gas-releasing reaction doesn't necessarily release a substantial amount of heat--some are even endothermic, meaning it absorbs heat and gets colder as it goes.
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Probably the best studied example is the decomposition of calcium carbonate to give carbon dioxide.
There is a pressure vs temperature chart here
https://en.wikipedia.org/wiki/Calcium_carbonate#Calcination_equilibrium
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simple reaction engineering
yes it will stop.. when the gas pressure stops the reaction generating the gas.
L'hopital (name roughly) discusses the driving forces on the rate of reactions I believe or at least the effect on the equilibria
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simple reaction engineering
yes it will stop.. when the gas pressure stops the reaction generating the gas.
L'hopital (name roughly) discusses the driving forces on the rate of reactions I believe or at least the effect on the equilibria
I think it's Le Chatelier (my recollection is that L'hopital contributed to calculus...)
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all them names hehe.. and yes you are right cheers chiral