R 1.4
No description yet. This curated deck is ready for daily study.
Card preview (24)
What is entropy and its symbol?
S a measure of distribution of energy in a system, disorder and randomness
How are particles in high entropy system?
particles spread out and move more
Why do systems tend to disorder?
more randomness as the energy is more dispersed
Entropy related to the 3 states of matter
least entropy: solid mid: liquid most entropy: gas
What happens to entropy during changes of state?
melting/vaporising: increase in ke, increases entropy condensing/freezing: decreases ke, decreases entropy
Which changes of state cause an increase in entropy?
from solid to liquid to gas –> as gases have higher entropy
What effect does creating a solution have on entropy?
increases entropy ions become dispersed between water molecules
In a chemical reaction, what do moles tell us about entropy?
increase in moles of gas -> increase in entropy and vice versa
What is the standard entropy of a substance?
entropy change from heating a substance from 0K to 298K always positive, since at 0K entropy is 0
The more ways energy can be distributed…
The higher the entropy
The higher the entropy…
The more ways energy can be distributed
standard entropy change for a reaction =
standard entropy of the products - standard entropy of the reactants
What is a spontaneous reaction?
a reaction that occurs without the addition of energy other than the Ea
What is the 2nd law of thermodynamics?
the total entropy of the universe tends to increase
total entropy =
total entropy of system + total entropy of surroundings
What is a spontaneous reaction?
a reaction that occurs without the addition of energy other than the Ea
What happens in a spontaneous process?
energy goes from a concentrated form to a dispersed form
Change in entropy in the formation of crystals from a salt solution?
crystals (system) have a lower entropy, but solvent molecules which are vaporised increase in entropy
How to calculate the entropy of change of the surroundings?
negative enthalpy change of process/absolute temp in Kelvin
What is the sign for the entropy change of the surroundings and why?
heat is given out by the system to the surroundings, so a decrease in enthalpy means an addition of heat to surroundings so it is positive when heat is given out (opposite to system)
Equation for change in standard Gibbs energy:
ΔG = ΔH - TΔS (s is the standard entropy)
What does a change in Gibbs energy mean?
direct entropy change resulting from the transformation of the chemicals + the indirect entropy change of the surroundings resulting from the transfer of heat energy
Detail the conditions of each reaction and whether they will be spontaneous or not regarding enthalpy and entropy.
endothermic and decrease in entropy - never spontaneous endothermic and increase in entropy - spontaneous when temp. is high exothermic and increase in entropy - always spontaneous exothermic and decrease in entropy - spontaneous when temp. is low
What does Gibbs energy need to be for a reaction to occur?
spontaneous - negative non-spontaneous - positive equilibrium - 0