Thermodynamics Flashcards
What is thermodynamics?
It is the study of change in temperature of a body
Define the following terms
1. System
2.Surrounding
3.Universe
- System can be defined as the body who’s temperature change is been studied
- Surrounding: everything that surrounds the system
3.Universe: the system and the surrounding together
What are the different types of system?
The different types of system are:
1. Closed system: no transfer of matter
2. Open system: energy and matter both are transferred
3. Isolated system: no transfer of energy and matter both
What are the different types of process?
- Isochoric: the volume stays constant
- Isobaric: the pressure stays constant
3.Isothermal: the temperature stays constant
4.Adiabatic: an isolated system process
What is path function and state function?
Path function are those variable that depend on the was that state is attained like work, heat
While state function depends on the initial and final state of the system like V, P,TT enthalpy
Classify Heat capacity and specific heat capacity on the bases of intensive and extensive properties ?
SI unit of C(heat capacity) = J/k
SI unit of c(specific heat capacity) = J/K kg
thus heat capacity is intensive and specific heat capacity is extensive
What is the formula to calculate the work done in a reversible process ?
-2.303Rt log(pi/pf)
or
-2.303Rt log(Vf/Vi)
What are intensive and extensive properties?
Intensive properties are those that are independent of mass like density, temperature, pressure and
while extensive are those that depend on the mass of the substance like volume, enthalpy ,gibis free energy
Work =
F.d = -PΔV
What is the first law of thermodynamics ?
The first law is
ΔU = Q + W
= Q -PΔV
2nd law
Exothermic reaction is spontaneous due to the release of energy during the process that increases the temperature
ΔS>= 0
3rd law
When the temperature hits 0 k or -273.15 C then the spontaneity of aa solid crystalline is zero
What are the sign conventions for the following:
1. work done on the system
2. Work done by the system
3. Endothermic reaction
4. Exothermic reaction
- ve
- ve
- ve
- ve
Enthalpy
A state function that measures the the total change in the energy levels of a system.
ΔH =ΔU +PΔV
ΔU means
internal energy or the sum of all the Ke and PE of the system
it depends only on temperature
ΔH =
(for gases)
pΔV = ΔngRT
ΔH = ΔU +ΔngRT
Δng = products - reactants (moles)
What is Standard enthalpy? And what are their types?
Standard enthalpy is the enthalpy measured at 1 atm pressure and 298 K . There are two types:
1. Standard enthalpy of formation(ΔfH): it concentrates on the number of moles formed.
ΔfH = ΔrH/ no of moles in the product
- Standard enthalpy of reaction(ΔrH): this mainly focuses on the enthalpy change
What are different type of enthalpy? (on the bases of state change)
- Enthalpy of fusion (ΔfusH ): amount of energy required to convert 1 mole of solid into liquid.
Δ H = +ve - Enthalpy of vaporization (ΔvapH): the energy required to convert 1 mole of liquid into vapours at boiling point
Δ H = +ve - Enthalpy of sublimation(ΔsubH): the energy required to change 1 mole of solid directly into gas
Δ H = +ve
Hess’s law
that the change of enthalpy in a chemical reaction is the same regardless of whether the reaction takes place in one step or several steps, provided the initial and final states of the reactants and products are the same.
Δ T = 0
Δ Ht = Δ H1 + Δ H2…….
What are the different types of standard enthalpy (on the bases of reaction)?
- Combustion (ΔcH∘): energy required to burn 1 mole of a substance
- Atomization(ΔaH∘): energy required to break one mole f a compound into atoms
- Lattice(ΔlatticeH∘): energy required to break 1 mol of ionic compound into ions in gaseous state
- Solution(ΔsH∘): energy required to add 1 mol of solute in a specific solvent
- Dilution(ΔdH∘): the change in the value of ΔH when solvent is added
What is thermal equation?
it a balanced equation with the value of ΔH given
Bond harbor’s cycle
It is a method used to calculate the standard lattice enthalpy change of a reaction by using other types of enthalpy change leading to ionization
Entropy
the measure of disorderness or randomness in a substance
Factors
1. heat
2. temperature
ΔS = 0 reversible reactions
ΔS > 0 for irreversible reactions
Spontaneity
Self occurring reaction. A reaction that doesn’t need external interference to happen.
Factors:
1. entropy
2. enthalpy
Gibbs free energy
A state function that tells about the spontaneity of a reaction
ΔG = ΔH - TΔS
ΔG>0, ΔH > TΔS not spontaneous
ΔG<0, ΔH < TΔS spontaneous
