How the tendency of a process to occur by itself is distinct from how long it ta

Question

How the tendency of a process to occur by itself is distinct from how long it takes to occur The distinction between a spontaneous and a non-spontaneous change. Why the first law of thermodynamics and the sign of Delta H^0 cannot predict the direction of a spontaneous reaction The natural tendency of a system to become disordered over time and why a disordered system is more probable than an ordered one How disorder is expressed quantitatively by entropy (S) How the second law of thermodynamics expresses the criterion of spontaneity, that a change increases S_univ How absolute entropies (S degree) can be obtained because the third law of thermodynamics provides a "zero point" How temperature, physical slate, dissolution, molar mass, and molecular complexity influence S degree values How Delta S degree_rxn is based on the difference between the S degree values of the reactants and the products How the surroundings add heat to or remove heat from the system and how Delta S_surr degree influences the overall Delta S_rxn. The relationship between Delta S_surr degree and Delta H_sys degree How reactions proceed spontaneously toward equilibrium (Delta S_univ degree > 0) and then proceed no further at equilibrium (Delta S_univ degree = 0) How the free energy change combines the system's entropy and enthalpy changes How the expression for the free energy change is derived from the second law The relationship between Delta C and the maximum work a system can perform and why this quantity of work is never performed in a real process How temperature determines spontaneity for reactions in which Delta S degree and Delta H degree have the same sign Why the temperature at which a reaction becomes spontaneous occurs when Delta G degree = 0 How Delta G degree is the free energy change from the start of a reaction (expressed by Q) to its end (expressed by K) The meaning of Delta G degree and its relation to K The relation of Delta G to Delta G degree and Q How Delta G decreases, no matter what the starting concentrations, as the reacting system moves spontaneously toward equilibrium

Explanation / Answer

1) The tendency of the process to occur by itself takes are spontaneous processes which can happen
naturally without being driven by any outside energy and the time taken for the reaction to reach
completion is not known, Whereas for non-spontaneous processes you can predict time

2) Spontaneous change are irreversible whereas non-spontaneous are reversible

3) The overall change in energy for the system + surroundings = 0, thereforewe cannot use the change
in energy of a system to predict whether a reaction will occur.

4) Spontaneity of a process depends not only upon the enthalpy change but also upon how the
    disorder of the system change. Predicting the reaction direction and energy changes would be
   tough for a sytem that is in order.

5) Entropy is a degree of randomness, S = qreversible / T

6) second law of TD states that  a process involving an isolated system will be spontaneous if
   the entropy of the system increases over time
     Stotal =  Ssys +  Ssurroundings (Suniv)   0
This criterion can be used to explain how it is possible for the entropy of the system to decrease during a spontaneous process

7) The third law of TD provides a fixed reference point that allows us to measure the absolute entropy
    of any substance at any temperature.

8) Dissolution and molar mass do not influence the So , it only depends upon the temperature
   and the physical state for a perfect crystal

9) S° = n S°(products) – m S°(reactants)

10) Few processes liberate energy during the reaction and hence release energy in to the surroundings .
Srxn goes in according with the  Ssur . Srxn depends upon heat changes made in reaction
whereas Ssur depends upon heat changes in surroundings. So, you can relate the heat changes
   to know the influence of  Ssur on  Srxn   

11) Ssur = - Hosys /T , reversible conditions are assumed

12) Suniv = Ssurr + Ssys
If reactions proceed toward  Suniv=0 then Ssurr = -  Ssys which is impossible
Always Ssurr >  Ssys , that is the reason why Suniv > 0

13) G = H - TS

14) Stotal = Ssurr + Ssys
you know Ssur = - Hosys /T , multiply the above equation with T and -1
   -T Stotall = Hosys - TSsys
   G = H - TS

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