Thermochemistry Flashcards
What is gibbs free energy?
Gibbs free energy combines enthalpy and entropy into a single value. This quantity is the energy
associated with a chemical reaction that can be used to do work.
How does Gibb’s energy affect spontaneity?
Spontaneity decreases with gibbs energy.
What is the formula for gibbs energy?
ΔGo = −nF Ecello
Where: ΔGo is the standard free energy change n is the number of transferred electrons Eo is the standard cell potential F is the Faraday constant = 96500 C mol-1
What is Faradays constant?
96500 C mol-1
Formula for Nernst equation
E = Eo − (RT/ nF ) ln ( ([Product]) / [Reactant] )
E is the cell potential
Eo is the standard cell potential
R is the universal gas constant = 8.314 J/K/mole
T is the temperature
n is the number of transferred electrons
F is the Faraday constant = 96500 C mol-1
.
What is the universal gas constant?
8.314 J/K/mole
What are the main types of systems in thermochemistry?
Isolated, closed, and open.
What is an isolated system?
No anything in or out.
What is closed system?
No exchange of matter
What are thermodynamic properties?
Thermodynamic properties are defined as characteristic features of a system, capable of
specifying the system’s state.
Examples of thermodynamic properties
- Pressure
- Temperature
- Volume
- Entropy
- Internal energy
- Enthalpy
- Gibbs function
- Helmholtz functions.
How many types of physical properties of a system are there?
- Intensive and extensive.
What are intensive properties?
Intensive properties are properties that do not depend on the quantity of matter.
What are extensive properties?
Extensive properties are properties whose value depends on the mass of the
system.
What are examples of physical properties of a system.
Helmholtz free energy (F) Gibbs free energy (G) Enthalpy (H) Internal energy (U) Entropy (S) Volume (V) Temperature (T) Pressure (P)
What is enthalpy?
Determines the capability of a system to do work and release heat.
What is gibbs energy?
The thermodynamic potential that measures the maximum or reversible work by a thermodynamic system. Determines the feasibility of a reaction.
What is Helmholtz free energy?
The thermodynamic potential that measures useful work done by a closed thermodynamic
system
How many types of thermodynamic processes are there?
- Isobaric, isochoric, isothermal, adiabatic
What is an isobaric process?
• An isobaric process, during which the system’s pressure does not change.
What is isothermal process?
• An isothermal process, during which the system’s temperature remains constant.
What is adiabatic process?
• An adiabatic process, during which no heat is transferred to or from the system.
What is isochoric process?
• An isochoric process, during which the system’s volume does not change.
What is formula for enthalpy change?
ΔH = ΔU + ΔPV
where H = Enthalpy U = Internal energy P = Pressure V = Volume
What are the main types of enthalpy changes?
- Enthalpy change of formation.
- Enthalpy change of neutralization.
- Enthalpy change of combustion.
- Enthalpy change of reaction (generalized)
What is standard enthalpy change of formation?
The standard enthalpy of formation is defined as the change in enthalpy when one mole
of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its
pure elements.
What is enthalpy change of reaction?
The standard enthalpy of reaction is the enthalpy change that occurs in a system when a
chemical reaction transforms one mole of matter under standard conditions (1 atm of
pressure and 298 K). Generalized term.
What is Hess’s law?
Enthalpy change for a reaction is independent of the number of ways a product can be
obtained, if the initial and final conditions are the same.
What is the second law of thermodynamics?
In a spontaneous process the
entropy of the universe
increases.
Formula for Gibb’s free energy
ΔG=ΔH−TΔS
What do endogornic and exogornic reactions relate to
Gibbs energy
What is a solution?
A solution is a homogeneous mixture of two or more substances and can
either be in the gas phase, the liquid phase, the solid phase.
Factors affecting solubility
• Nature of solute:
Like dissolves like.
• Temperature:
In case of liquids and solids, solubility increases with an
increase in temperature. For gases, it decreases.
• Pressure:
Does not affect most solids and liquids. In case of gases,
solubility is directly proportional to pressure
What is Henry’s law?
Cg =kPg
where C is solubility, P is pressure and k is
proportionality constant that depends on temperature and nature of solvent
What is molarity?
Moles of solute/ Liter of solution
What is molality?
Moles of solute/ kg of solution
What is mole fraction?
Moles of solute/ total moles in solution
What is parts per million?
(Mass of solute/ mass of solution)*10^6
