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Define dynamic equilibrium state

  1. May 9, 2005 #1

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    I have to define dynamic equilibrium state in terms of a) reaction rates b) change in observable properties and c) energy and entropy state

    I also have to explain in which of the following closed containers has the greatest vapour pressure.
    the choices are a) 1L container with 5mL of water held at 20degreescelcius
    b) 2L container with 15mL of water held at 30degcel
    c) 3L containter with 500mL at 25degcel

    finally, ethanol and water are completely miscible; that is, they dissolve in each other in all propertions:
    a) when the two substances are mixed, is randomness increased or decreased?
    b) heat is liberated in the dissolving process. Does the tendency towards minimum energy favour the seperated pure substances, or the solution of one in the other?
    c) In view of the tendicies listed in a) and b) above, explain why water and ethanol are completley miscible.

    My answers are as follows:
    Reaction rates are equal in a dynamic equilibrium state. The concentration of reactants and products remain constant over time due to forward and reverse reactions occurring simultaneously. Two opposing processes are going on at an equal rate and the system undergoes no observable changes.
    b) Change in observable properties in an equilibrium state is none. The forward and reverse reactions are equal and no changes can be seen.
    c) Energy and entropy states are in competition with each other. When a system is in equilibrium the two opposing drives have said to have reached a compromise and are equal.
    2)The b equation would have the greatest vapour pressure due to the highest temperature. When a stress is added to a system like increased temp. of 30oC the system tries to level to regain equilibrium. This results in an increase in concentration of the vapour state. The increased concentration also increases the pressure. I also used PV= nRT and b was the one with the highest pressure.
    3.Randomness would be increased as when two substances are completely miscible. When randomness increases the two substances are allowed to completely mix together. The entropy of the system is increased.
    b) General entropy of the system has increased then that can mean that the enthalpy would favour the separated pure substances.
    c) With these two points explained we can say that ethanol and water are completely miscible because an equilibrium has been formed between the two systems
     
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