Thermochemistry/Thermodynamics Flashcards
What is a system?
This is everything that is enclosed in a vessel and everything that you are observing.
What is a surrounding?
This is everything asides from the system.
What is the universe?
This includes both your system and the surroundings.
What is the internal energy?
This is the total energy of the system.
What happens in expansion?
There is a larger volume and the system is doing the work.
What happens in compression?
There is a smaller volume and the surrounding is doing work on the system.
What is pressure-volume work?
The change in volume with a constant external pressure.
What 2 things do we look at when finding pressure-volume work?
- ) Same system ( mols and pressure)
2. ) Different volume
What happens to heat for an endothermic reaction?
The heat is being absorbed with a +Q.
What happens to heat for an exothermic reaction?
The heat is being released with a -Q.
What are the standard conditions for thermochemistry?
Pressure = 1 bar Temperature = 273 K
What is enthalpy?
This is a state function where the start and ends only matter not the pathway.
How do you know if there are multiple steps to get to the final enthalpy?
The number of arrows to get to the final enthalpy determines the number of steps of the mechanism.
What is a standard state?
This is the most stable form of the material under a given condition.
What is Hess’s Law?
The total enthalpy change does not change no matter how many steps you have.
What is the enthalpy of formation?
The change in enthalpy during the formation of 1 mole of a substance from its constituent elements.
When is the heat of formation zero?
When looking at individual elements.
What is the bond dissociation energy?
The energy required to break one mole of bonds.
What are the assumptions?
- ) Only looking at the net picture and other interactions are not taken into account.
- ) Rest of the molecule affects the energy required to break the bonds.
What is a soluble salt?
These salts dissociate 100% into water K»»»1 ions will only react if the “conjugate” they make is a weak acid or base.
What are insoluble salts?
These are sparingly soluble salts that do not dissociate very much K«<1 solid salts are in equilibrium with ions.
What happens with a large Ksp?
- More products are favoured
- More salts are dissociated
- With more soluble salts
What happens with a small Ksp?
- More reactants favoured
- Less salt dissolves
- With a less soluble salt
What is a supersaturated solution?
Q>K = shift left, reactants are favoured
What is a saturated solution?
Q=K = No effect at equilibrium
What is an unsaturated solution?
Q
What factors affect solubility?
- ) Temperature
- ) Common-ion effect
- ) Side reactions
- ) pH
What is a spontaneous reaction?
The reaction may require a jump start however no continuous external assistance is required a reaction may be slow and spontanous.
Does spontaneous mean immediate?
No, spontaneous does not mean instantaneous.
What is a nonspontaneous reaction?
Products can still be obtained but continuous external assistance is required.
What is Gibb’s Free energy?
This identifies the variables of spontenaity.
What is entropy?
The measure of randomness/disorder of the matter or energy in a system.
What is the 3rd Law of Thermodynamics?
The entropy is 0 and there a perfect crystalline structure with perfect crystals and perfect alignment.
What factors impact entropy?
- ) Temperature
- ) Physical state
- ) Number of particles in the sample
- ) Size complexity of the molecules
How does entropy increase?
- ) Solid -> Liquid -> Gas
- ) Increase in temperature
- ) More particles
- ) Heavier atoms
How does entropy decrease?
1.) Solid
What is the 2nd Law of Thermodynamics?
The entropy of the universe will always increase.
S > 0?
Spontaneous
S = 0?
Equilibrium
S < 0?
Non-spontaneous
What is the Gibb’s free energy sign for the spontaneous reactions?
Negative
What is the Gibb’s free energy sign for the nonspontaneous reactions?
Positive
What happens to spontaneity when Q < K?
The forward reaction is spontaneous.
What happens to spontaneity when Q = K?
The reaction is at equilibrium so the G = 0.
What happens to spontaneity when Q > K?
The reverse reaction is spontaneous.
