chemistry ?

Discussion in 'General Science' started by Mathematics!, Jan 10, 2010.

  1. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
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    Ok , I am looking for somebody that is a chemical expert to answer this question.... or what the state of a reasonable answer would be

    I am wonder about chemical reactions
    Their are 2 types reversable and irreverable chemical reactions.

    What I am wondering is the difference between them...
    I.e is it just that we haven't found a method to reverse irreversable reactions or has it been proven that no irreversable reactions could ever be reversed???

    Or is irreversable reaction something that maybe reversable but not efficantly or does not have a method to do it yet but not proven impossible???

    Also question 2 is their a mathematical way of looking at a chemical reaction and determining it is a reverseable or irreversable reaction? ( or at least being able to determine if something is reversable )

    For example looking at the rechargeable lead acid batteries chemical reactions and a nonrechargeable AA batteries chemical reaction is their away to determine which one was rechargeable or not by looking at the reaction formulas ?

    Thanks for any help
     
  2. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    antidote for chemical. Battery acid will burn skin,will cause explosion,concusion
    could kill.
     
    Last edited: Jan 11, 2010
  3. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
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    this doesn't answer my question.

    I am wondering what the answers if their are any methods of determining if a reaction is reversible or not for get the battery example for a second?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
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    Hello,

    Take a look at this page:
    http://www.cem.msu.edu/~reusch/VirtualText/aldket1.htm
    A bit down is this "chapter" :reactions of Aldehydes and Ketones
    That is splt in two parts reversible and irreversible reactions.

    This ia a link from the organic chemistry page of the EDUCYPEDIA:
    http://www.educypedia.be/education/chemistryorganic.htm

    There are more pages like that over there:

    Chemistry: Acids and bases Distillation Inorganic chemistry Atoms Electrochemistry Miscellaneous Organic chemistry Biochemistry Food chemistry Molecules Spectroscopy Crystals General Nomenclature Stoichiometry
    Greetings,
    Bertus





     
  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    This is a pretty good description of irreversible chemical reaction:

    http://www.wordiq.com/definition/Chemical_reaction

    The Wikipedia description is also pretty good. Also, look up microscopic reversibility.

    As for predicting whether a reaction will be irreversible, there are several characteristics to consider. All of the references mention them, such as when the product precipitates or escapes from the reaction mixture. Some reactions may not appear to be reversible, but actually can be shown to be reversible using isotopic and other methods. Reactions in which the equilibrium constant is very much in favor of products are also called effectively irreversible.

    Irreversible has a slightly different connotation with respect to enzymatic reactions.

    Finally, be cautious of using trivial examples such as the burning of wood for irreversible reactions. Sure, that process cannot be reversed, but it involves many reactions and biological structures. It is akin to saying that life is irreversible, yet life would not exist if it were not for countless reversible reactions.

    John
     
  6. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
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    This seems like an unsolved question because who's to say that if you burn a piece of paper and trap all the atoms ... who's to say that their will never exist a chemical reversale process for it....

    Unless their is some proof out their that say's you can never reverse this particular process...?

    As for the definitions of reversible /irreverisble reactions ... even these are up for depate because if every thing in theory can be reversed then the reversible reactions = irreversible reactions they would be one in the same thing...
    And the question would be anologious to the computer science question P = NP ?

    Forgetting all this for a moment is their any reasonable way given a chemical reaction to determine if it is reversible ( or at least if we have a method for reversing it) . If this is to general then my question would be given any chemical reaction is their away to determine if it is reversible based on the fact that you can only use electrical current , tempature (states of matter) to do it with?

    What I mean is just using current or changes in states of matter but not additional chemicals or anything else to reverse the process...

    Thanks
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    I suggest you re-read my comment and the references I gave with it. Quite obviously, you cannot prove any negative.

    Yes, within the limits described previously.

    Temperature does not equate to states of matter. What do you mean by that?

    Again, you seem to be missing the point about the definition of a reversible reaction.

    John
     
  8. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Well yes of course there is but

    First you have to state your reaction.

    This statement has to be completely specific, a balanced chemical equation.

    When you have this you must next realise that the terms 'reversible' and 'irreversible' strictly are thermodynamic terms.

    Armed with these pieces of information you can proceed to calculate the enthalpies of all the substances present in your equation. A balance of these will establish the thermodynamic conditions for reversal.

    Once you have calculated these you can then use statistical dynamics to calculate the rate at which your equation would proceed. This is not related to the thermodynamic properties of the system. Many thermodynamically favourable reactions do not proceed at appreciable rates for statistical reasons.
     
  9. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    If the north and south poles can reverse,that means a lot
    unanswered questions exist.You pose some good questions
    for debate.Things happen what if you just rewind the video,
    you can reverse anything,now figure out the rest of the
    formulas that interest you.
     
  10. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
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    I guess that question I post was to much unsolved....
    Let me go more restrict on it is their away distinguish what batteries are rechargeable or not rechargeable based on the chemical formulas,...
    Like looking up AA , or Ni-CAMD ,...etc
    How can you determine if electricity can reverse these chemical formulas....

    I went thru the lead acid battery chemical equations and I get how the reaction gives off electrons ,...etc but I don't know why the reversal process can happen for this and not for some other AA chemical reactions ,....etc

    How would you determine this from the equation?
     
  11. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    I guess that question I post was to much unsolved....
    Let me go more restrict on it is their away distinguish what batteries are rechargeable or not rechargeable based on the chemical formulas,...
    Like looking up AA , or Ni-CAMD ,...etc
    How can you determine if electricity can reverse these chemical formulas....

    I went thru the lead acid battery chemical equations and I get how the reaction gives off electrons ,...etc but I don't know why the reversal process can happen for this and not for some other AA chemical reactions ,....etc

    How would you determine this from the equation?
     
  12. Thevenin's Planet

    Active Member

    Nov 14, 2008
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    In a twinkling of an eye!
    Is it magic,spells,incantations,that is chemical formulas,structural formulas or molecular models.Are they equivalents, a figure of our imagination or some empirical experiments that reflects the actual chemical function(s).Perhaps the answer lies beyond earth to find materials that would achieve reversible reaction.I am wondering how close do the various formulas and molecular models expresses the actual combining and manifestation of changes.The symbols that expresses a particular chemical activity is different in many situations.Temperature,pressure,and composition of mixture is the things are taken in consideration.Is there more then what the scientist have discovered.hOW MUCH BIOLOGY CAN PLAY A PART IN THE REVERSE REACTION?
     
    Last edited: Jan 12, 2010
  13. rvh002@gmail.com

    Active Member

    May 15, 2009
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    I am going to try and explain this with some example. If you put Hydrocloric acid(HCL) into your pool to fix the PH, it reacts with the carbonates (Hard water or soft water) and neutralizes the PH of the water. This is necessary so that the chlorine compound can do its work and remove/destroy the algea. Once the acid has reacted with the carbonates it forms a sediment. This sediment (I can Elaborate if somebody wants) can not be reversed. IE this reaction is one way (under normal conditions)

    The chemical reaction in a "fixed" battery is the same. Once it has gone it's way, it is finished.
    In a rechargeable battery the situation is slighly different: The basic lead acid battery allows about 500 recharges before it packs up(chemically) That means that the chemical reaction that produces the energy can be reversed and activated by an external charge (alternator/battery charger) at any point in time.
    After a time (X) this process stops because the plates in the battery clogs up with chemical residue. This is not reversable!. This means the battery needs to be replaced.
    The same applies for new design bateries: NiMh, or any version up to Nipoly bateries all have the same problem: they can take a lot of charge for a long time but in the end they can only last "so long" The chemical reaction inside the battery can not be reversed.
     
  14. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    Your burned paper can be reversed.there are processes to
    read burn't paper. You are lucky that many members
    read and retain some facts outside there occupation
    or education area's.There are so many chemicals that
    react to things in many forms. If it were not for the information
    age.More thing are solved because money is not the factor
    for the reason it is solved. You cannot count the special labs
    that exist,that you will hear about only by getting a glimpes
    on the t.v. unrelated to most things.It is cheaper for the
    medical examiner to state cause of death,(heart stopped)
    than all the test available to preform.We expect so much from
    science,our body,the earth,medicine, uncounted things.
    So we belive in god,(deity) to know all the answers.
    The perfect death.
     
    Last edited: Feb 14, 2010
  15. retched

    AAC Fanatic!

    Dec 5, 2009
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    You want to know, if by looking at an equation, you can determine if the checmicals that make electricity can be converted BACK into the original components by ADDING electricity.

    IE. lead-acid batteries- The acid eats lead and makes a sulfate while releasing electrons. If you add electrons to the sulfates, they return (not 100%) to acid and lead to start the process over again.

    It may be easier to think backwards. Find a substance(A) that when power is applied(A + power), separates into 2 or more substances(B+) and (C+). Now you have a few substances(B+) and (C+). If you add them back to each other(B)+(C), they should produce the original substance plus electrons(A)(+)
     
  16. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    Like I say the Info come from all directions,from every one.
     
  17. rvh002@gmail.com

    Active Member

    May 15, 2009
    118
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    Keep in mind that charging a battery is adding lost "energy" NOT reversing the discharge process. Any battery, from lead-acid to Lith-pro, can only be recharged "x "amount of times. This is not reversing the discharge process, but adding "energy" so that it can discharge again. After "x" amount of discharges the chemical elements in the battery are depleted (used up) and can not be used again. This is a very basic explenation of how a battery works. Hope it puts a bit of light on the subject.
     
  18. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Actually 'adding electricity' does indeed cause chemical changes within a discharged battery, that reverse the chemical changes that occur to supply the energy.
    Unfortunately other undesireable chemical changes also occur during the charge discharge cycles, which in time 'poison' the operation of the batttery.

    What you say applies to capacitors, which are not primary energy sources, not to batteries which are primary energy sources.

    There is, of course, a corresponding difference in circuit theory between capacitors and batteries, it's called EMF.
     
  19. ChrisChemist116

    Active Member

    Mar 13, 2009
    78
    1
    Mathematics, your question is very interesting.

    But, you haven't specified field in chemistry that is related your question regarding reversible and irreversible reactions.
    Depending on the field (let's say, physical chemistry, organic chemistry, etc..) you will find different approaches to your matter.

    Maybe if you can specify that, i can assist you.
     
  20. johndoe45

    Member

    Jan 30, 2010
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