Gibb’s Energy & Thermodynamics Flashcards
What does entropy describe?
the dispersion of energy
What is a spontaneous process?
occurs without ongoing external intervention
Can spontaneous reactions be slow?
yes
What is entropy? (definition)
a thermodynamic function that increases with the number of equivalent ways to arrange the energy among components of the system to acheive a particular overall state
How is entropy mathematically described? What are the variables?
S=klnW
S is entropy, k is a constant (1.38x10^-23 JK^-1), W is the # of equivalent energy arrangments in the system (microstates)
Explain why water has greater entropy than ice using microstates?
more ways to distribute the energy in water than ice because they can more more, therefore more microstates
What is the second law of thermodynamics?
for any spontaneous process the entropy of the universe increases
How do non-spontaneous reactions effect the entropy of the universe?
do not increase or decrease it
What is the formula for the change in entropy?
deltaS=Sfinal-Sinitial
If entropy increases how does temperature change?
increases
What increases entropy?
adding more particles, melting, sublimation, evaporation
What is the formula for the entropy of the universe?
Suniverse=Ssys + Ssurr
How does the entropy of the surroundings change for exo/endothermic reactions?
exothermic increases the entropy of surroundings
endothermic decreases the entropy of surroundings
At a constant temperature and pressure how can you find the entropy of the surroundings?
deltaSsurr=-deltaHsys/T (kelvin)
How can you find the change in entropy of the universe?
deltaSuni=deltaSsys - deltaH/T
How is Gibb’s free energy related to entropy?
deltarG=deltarH - TdeltarS
If enthalpy is exothermic and the entropy increases what is the sign for gibb’s free energy?
always negative no matter the temperature
If enthalpy is endothermic and the entropy decreases what is the sign for gibb’s free energy?
always positive, no matter the temperature
If enthalpy is exothermic and the entropy decreases what is the sign for gibb’s free energy?
negative at a low temperature and posititve at a high temperatureq
If enthalpy is endothermic and the entropy increases what is the sign for gibb’s free energy?
posititve at a low temperautre and negative at a high temperautre
How can you calculate deltarS0?
the sum of coefficients multiplied by standard molar entropies of the products minus the sum of coefficients multiplied by standard molar entropies of the reactants
like standard enthalpy
What is the enropy of a pure crystal at 0K?
0
How does molar mass contribute to entropy?
heavier atoms have a higher entropy, larger noble gases have a higher entropy
How does molecule complexity relate to entropy?
more complex molecules have a higher entropy
What are the methods to calculate deltarG0?
using standard Gibb’s energy of formation, table is only valid for 298K, calulate standard enthalpy and standard entropy and have T, similar to hess law
At standard state conditions what is Q?
1
If deltarG0 is greater than 0, what is the relationship between Q and K?
Q is greater than K
If deltarG0 is less than 0, what is the relationship between Q and K?
Q is less than K
If deltarG0 is equal to 0, what is the relationship between Q and K?
Q is equal to K
How can you calculate deltarG under non standard conditions?
deltarG=deltarG0 + RTlnQ
How can you find deltarG0 if you know K?
deltarG0=-RTlnK
If you have two K’s and two temperautre what formula can you use?
ln(K2/K1)=-deltarH0/R(1/T2-1/T1)
