5.2.2: Enthalpy and entropy Flashcards
Define entropy
A measure of the dispersal of energy in a
system which is greater when the system
is more disordered
What is the symbol of entropy?
S
Solid or gas, which is more disordered?
Gas
What is the unit of standard entropy?
J K-1 mol-1
How does temperature affect entropy?
The greater temperature particles have more energy and move more. Thus the arrangement of particles become more random. More random arrangement = higher entropy
When a solid ionic lattice is dissolved in solution
what happens to entropy?
Entropy increases because the ions are
more disordered
Entropy increases because the ions are
more disordered?
Increase in number of gas molecules = increase in entropy
Decrease in number of gas molecules = decrease in entropy
Write the Gibbs’ free energy equation and state what
each symbol means
ΔG= ΔH - TΔS ΔG= gibbs free energy/available energy ΔH= enthalpy change T= temperature in kelvin ΔS= entropy change
Fill in the blanks ΔH = negative ΔS = positive ΔG =? Feasibility of spontaneous change=?
ΔG = always negative
Feasibility of spontaneous change= reaction feasible
Fill in the blanks ΔH = positive ΔS = negative ΔG =? Feasibility of spontaneous change=?
ΔG = always positive
Feasibility of spontaneous change= reaction never feasible
Fill in the blanks ΔH = positive ΔS = positive ΔG =? Feasibility of spontaneous change=?
ΔG = negative at high temperatures
Feasibility of spontaneous change= feasible at high temperatures
Fill in the blanks ΔH = negative ΔS = negative ΔG =? Feasibility of spontaneous change=?
ΔG = Negative at low temperatures
Feasibility of spontaneous change= Reaction feasible at low temperatures
For a reaction to occur spontaneously ΔG must be
positive or negative?
Negative
What are the limitations of the predictions of
feasibility made by using ΔG? (2 marks)
● Reaction may have high activation energy
● Rate of reaction may be very slow
