Thermodynamics 17.1-17.3 Flashcards
Exam 3
What is the first law of thermodynamics?
Energy cannot be created or destroyed, however energy can be converted from one form to another
System
The molecules involved in the reaction taking place
Surroundings
What contains the system
When heat is absorbed by the system,
+q ; Endothermic; System is lower than surroundings
When heat is given off by the system,
-q; Exothermic; System is higher heat than the surroundings
Endothermic is +heat on the
Reactant Side
Exothermic is +heat on the
Product Side
Spontaneous processes
Precedes without the continual input of energy from an external force
Entropy
A measure of the amount of disorder in a system
The more disorder in a system, the more
entropy within the system
Is entropy a state function like enthalpy?
Yes
When energy is dispersed, enthalpy increases/decreases
increases
What is the second law of thermodynamics?
Entropy of the universe will increase for a spontaneous process
Microstates
Number of different snapshots is needed to describe all possible arrangements of a system
As temperature increases, Entropy increases/decreases
Increases
As temperature decreases, Entropy increases/decreases
Decreases
As volume decreases, Entropy increases/decreases
decreases
As pressure decreases, Entropy increases/decreases
Increases
Moles on the reactant are greater than the products, Entropy increases/decreases
decreases
Moles of the products are greater than the reactants, Entropy increases/decreases
Increases
Is the phase change from solids->liquid->gas or is it gas->liquid->solids
solids->liquid->gas
Does the entropy increase or decrease:
4Fe(s) + 3O2(g) -> 2Fe2O3 (s)
Decrease; Inaccurate phase change
solid to liquid
Melting
Liquid to solid
Freezing
Liquid to gas
Evaporation
Gas to liquid
Condensation
Solid to gas
Sublimation
Gas to solid
Deposition
Gas to gas
No phase change
If Enthalpy (H) is exothermic (-) and Entropy (S) is positive (+), the reaction will be
Always spontaneous
If Enthalpy (H) is endothermic (+) and Entropy is negative, the reaction will be
Always nonspontaneous
If Enthalpy (H) is endothermic (+) and Entropy (S) is (+), the reaction will be
Spontaneous at high temperatures and nonspontaneous at low temperatures
If Enthalpy (H) is exothermic (-) and Entropy (S) is negative (-), the reaction will be
Spontaneous at low temperatures and nonspontaneous at high temperatures
A given reaction is spontaneous at low temperatures and nonspontaneous at high temperatures. What can be said about enthalpy and entropy?
Enthalpy is - and entropy is -
