reactivity 1.4- entropy and sponteneity
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entropy
distribution of available energy among the particles
entropy of a system
the state of disorder of a system
how will a system and its surroundings tend to move
from a state of high order (low entropy) to disorder (high entropy)
entropy of univers
entropy of system + entropy of surroundings= always positive
describe entropy in a reaction which changes solid to liquid or liquid to gas
increase in entropy or disorder entropy is positive
describe entropy in a reaction which changes 4 mol -> 2 mol
lower entropy, decrease in disorder entropy is negative
describe entropy in a reaction which changes solid to gas
negative entropy
how do you calculate the change in standar free energy at 298 K for a given reaction
1- calculate enthalpy change= sum enthalpy of formation for products - sum enthalpy of formation for reactants 2- caculate change in entropy = sum entropy of products - sum of entropy of reactants 3- calculate change in gibs free energy= enthalpy change - Temperature (in kelvin) * change in entropy/ 1000 (entropy always in KJ)
if gibs free energy is positive
reaction is not spontaneuos
if gibs free energy is negative
reaction is spontaneuos
how do calculate the temperature in which a reaction becomes spontaneuos
=change in enthalpy/ (change in entropy/1000)(since units msut be in KJ) temperautre will be given in kelvin this calculation will give rise to the minimum temperature for a reaction to becme spontaneuos
If enthalpy change is negative (exothermic) entropy change is positive (increase in disrder)
gibs free energy will always be negative, reaction always spontaneous
If enthalpy change is positive (endothermic) entropy change is positive (increase in disorder)
gibs free energy is positive if, reaction not spontanuoes in cold (if T*change in entropy < change in enthalpy) gibs free energy is negative if, reaction is spontaneuos at higher temperatures ( if T*change in entropy> change in enthalpy) reaction more spontaneous at higher temperatures
If enthalpy change is negative (exothermic) entropy change is negative (decrease in disorder)
gibs free energy is positive when, not spontaneous reaction (T * change in entropy > change in enthalpy) gibs free energy is negative when, spontaneous reaction, (T * change in entropy < change in enthalpy) reaction more spontaneous at colder temperatures
If enthalpy change is positive (endothermic) entropy change is negative (decrease in disorder)
gibs free energy is always positive, reaction is never spontaneuos
when is gibs free energy= 0
when reaction is at equilibrium
when is entropy negative
reaction reactants have more mol products have less from gas to liquid liquid to sold gas to solid
when is entropy postivie
reaction reactants have less mol than products from solid to liquid liquid to gas solid to gas