Entropy change

  • Created by: Hindleyc
  • Created on: 25-11-18 19:43
What will a spontaneous process such as diffusion do?
Proceed on its own without any external influence
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What is Gibbs energy in this case?
-ve therefore entropy greater than Enthalpy
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A rxn that is exo will result in...
products that are more thermodynamically stable than the reactants which is a driving force behind many reactions and causes them to be spontaneous(occur without any external influence)
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What are some spontaneous reactions
endothermic
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What is entropy
Description of the number of ways atoms can share quanta of energy
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What if number of ways of arranging the energy is high
system is disordered and entropy is high
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so substances with more ways of arranging their atoms and energy (more disordered) have
a higher entropy
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Simpler compounds and pure substances tend to have lower
entropies than complex compounds and mixtures
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order of entropy low to high
Solid, liquid, gas
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What happens when a solid increases in temperature
entropy increases as particles vibrate more
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When is there a bigger jump in entropy
with boiling than melting as gases have large entropies as they are much more disordered
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at 0k what do substances have
0 entropy as there is no disorder as particles are stationary
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What will an increase in disorder and entropy lead to?
positive entropy change
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what can be used to predict if delta S is +ve or -ve
balanced chemical eqn
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when will a significant inc in the entropy occur?
if there is a change of state from solid or liquid to gas or there is a significant inc in number of molecules b/w product and reactant
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so what inc disorder
solid to gas, inc in number of molecules
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What will have zero entropy
perfect crystals at absolute zero. not elements in standard states
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what s not possible
substance to have standard enthalpy of less than 0
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What do data books list
standard entropies per mole for variety of substances
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UNIT of entropy
J/K/MOL
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EQN for entropy
sum of entropy of products - sum of entropy of reactants
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What is Gibbs free energy change
Term that combines the effect of enthalpy and entropy into one number
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What determines feasibility of a reaction
balance b/w entropy and enthalpy
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eqn
delta G= delta H -TdeltaS
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What is a reaction that has inc entropy (+ve delta S) and is exothermic (-ve delta H) will make..
delta G be negative and will always be feasible
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For any spontaneous change delta G will be
-ve
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Even if delta G is -ve there is still a possibility however that..
the reaction will not occur or will occur so slowly that effectively doesn't happen
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Why?
If rxn has a high activation energy the reaction will not occur
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delta G unit
Kj/mol
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delta H
KJ/mol
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T
kelvin +273
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delta S
J/K/Mol needs to convert to Kj/k/mol. /1000
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Steps
calc delta S. calc delta H. Calc delta G if +ve rxn not feasible
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As physical phase change like melting and boiling are equilibria what is the delta G for such changes
Zero
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when is a rxn feasible
when delta G is equal to 0 or negative
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T=
delta H/delta S
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What will changing temp do
Change value of -TdeltaS
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If reaction involves inc in entropy (delta S +ve) what will an inc in temp do
make it more likely that delta G is -ve and more likely reaction occurs
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If reaction involves decrease in entropy (delta S -ve) then what ill inc in temp do
make it less likely that delta G is -ve and less likely for reaction to occur
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If reaction has delta S close to 0 then temp ..
won't have large effect on feasibility of rxn as -TdeltaS will be small and delta G won't change much
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using y=mx+c what's gradient and y intercept
gradeint= -deltaS. y intercept= delta H.
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What does a positive gradient mean
delta S is -ve
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Why does slope change when y negative
ammonia liquify and entropy different
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Other cards in this set

Card 2

Front

What is Gibbs energy in this case?

Back

-ve therefore entropy greater than Enthalpy

Card 3

Front

A rxn that is exo will result in...

Back

Preview of the front of card 3

Card 4

Front

What are some spontaneous reactions

Back

Preview of the front of card 4

Card 5

Front

What is entropy

Back

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