Chemistry REVISION


•`color{green}["Thermodynamics"]`:The branch of science which deals with the study of different forms of energy and the quantitative relationships between them is known as thermodynamics.

•`color{green}["System and surroundings"]`:A system in thermodynamics refers to that part of universe in which observations are made and remaining universe constitutes the surroundings.

•`color{green}["Boundary"]`:The wall that separates the system from the surroundings is called boundary. This is designed to allow us to control and keep track of all movements of matter and energy in or out of the system.

•`color{green}["Open system"]`: In an open system, there is exchange of energy and matter between system and surroundings

•`color{green}["Closed system"]`: In a closed system, there is no exchange of matter, but exchange of energy is possible between system and the surroundings.

•`color{green}["Isolated system"]`:In an isolated system, there is no exchange of energy or matter between the system and the surroundings.

State of the system

•`color{green}["State function"]`:A physical quantity is said to be state function if its value depends only upon the state of the system and does not depend upon the path by which this state has been achieved.

Internal energy

•`color{green}["Internal energy"]`:Internal energy is the quantity that represents all the form of the energy of the system, i.e., kinetic and potential energies of the system.



First law of thermodynamics

•`color{green}["Isothermal process"]`: The process in which temperature of the system remains constant at each stage of the process. i.e. dT 0 =or , △T=0.

•`color{green}["Exothermic process"]`: The process in which heat is given out to the surroundings is called exothermic process. l.n this process, products are more stable than reactants because they have lower energy.

•`color{green}["Endothermic process"]`:The process in which heat is absorbed by the system from the surroundings. In this process, products are less stable than reactants because they have higher energy.

•`color{green}["Adiabatic process"]`: The process in which no exchange of heat takes place between system and surroundings. i.e. q = 0.

•`color{green}["Isobaric process"]`: The process which takes place at constant pressure is called an isobaric process.

•`color{green}["Isochoric process"]`: The process which is carried out at constant volume is called an isochoric process, i.e. dV or △V = 0.

•`color{green}["Cyclic process"]`: In cyclic process, the system in a given state goes through a series of different processes, but in the end, returns to its initial state. dE or △U = 0, dH or △H = 0


•`color{green}("Reversible process ")` : It is a process which is carried out infinitesimally slowly so that all changes occurring in the direct process can be exactly reversed and the system remains almost in a state of equilibrium with the surroundings at every stage of the process.

•`color{green}("Irreversible process ")` :An irreversible process is defined as that process which is not carried out infinitesimally slowly so that successive steps of the direct process cannot be retraced and any change in external conditions disturbs the equilibrium.




•`color{green}("Intensive Properties ")` :Those properties which do not depend on the quantity or size of matter present are known as intensive properties.

•`color{green}("Extensive Properties ")` : Those properties which depend upon the quantity of matter contained in the system.


•`color{green}["Heat Capacity (C). "]`:Heat capacity (C) of a sample of substance is the quantity of heat needed to raise the temperature of the sample of substance by one degree Celsius (or one kelvin).

•`color{green}["Heat Capacity at Constant Volume (Cv) "]`: It is heat capacity when the temperature of substance is raised by `1^0C` (kelvin), keeping volume constant.

•`color{green}["Heat Capacity at Constant Pressure (Cp) "]`: It is heat capacity when the temperature of substance is raised by `1^0C` (kelvin), while keeping pressure constant.

•`color{green}["Molar Heat Capacity"]`: It is heat capacity to raise the temperature of 1 mole of substance by `1 ^0C`or 1 kelvin.

•`color{green}["Specific Heat Capacity"]`: It is the quantity of heat required to raise the temperature of one unit mass (I g) by one degree Celsius or one kelvin.

•`color{purple}(q = c xx m xx Delta T)`

•`color{purple}(C_p -C_v = R)`

Measurement of `ΔU` and `ΔH` : Calorimetry

Hess’s Law of Constant Heat Summation :

Different types of enthalpy

•`color{green}["Reaction enthalpy"]`: The enthalpy change accompanying a reaction is called the reaction enthalpy.

•`color{green}["Standard Reaction enthalpy"]`: The standard enthalpy of reaction is the enthalpy change for a reaction when all the participating substances are in their standard states.

•`color{green}["Standard enthalpy of fusion"]`: The enthalpy change that accompanies melting of one mole of a solid substance in standard state is called standard enthalpy of fusion or molar enthalpy of fusion, `color{purple}(Δ_text(fus) H^(⊖))`.

•`color{green}["Standard enthalpy of vaporization"]`: Amount of heat required to vaporize one mole of a liquid at constant temperature and under standard pressure (1bar) is called its standard enthalpy of vaporization or molar enthalpy of vaporization, `Δ_text(vap)H^(⊖)`.

•`color{green}["Standard enthalpy of sublimation"]`:Standard enthalpy of sublimation, `color{purple}(Δ_text(sub)H^⊖)` is the change in enthalpy when one mole of a solid substance sublimes at a constant temperature and under standard pressure (`1` bar).

•`color{green}["Standard molar enthalpy of formation"]`: The standard enthalpy change for the formation of one mole of a compound from its elements in their most stable states of aggregation (also known as reference states) is called Standard Molar Enthalpy of Formation.

•`color{green}["Standard molar enthalpy of combustion"]`:Standard enthalpy of combustion is defined as the enthalpy change per mole (or per unit amount) of a substance, when it undergoes combustion and all the reactants and products being in their standard states at the specified temperature.

•`color{green}["Enthalpy of atomization"]`: It is the enthalpy change on breaking one mole of bonds completely to obtain atoms in the gas phase.

•`color{green}["Bond dissociation enthalpy"]`:The bond dissociation enthalpy is the change in enthalpy when one mole of covalent bonds of a gaseous covalent compound is broken to form products in the gas phase.

•`color{green}[ "Enthalpy of solution"]`: Enthalpy of solution of a substance is the enthalpy change when one mole of it dissolves in a specified amount of solvent.

•`color{green}[ "Enthalpy of solution at infinite dilution"]`:The enthalpy of solution at infinite dilution is the enthalpy change observed on dissolving the substance in an infinite amount of solvent when the interactions between the ions (or solute molecules) are negligible.

•`color{green}["Lattice Enthalpy "]`:The lattice enthalpy of an ionic compound is the enthalpy change which occurs when one mole of an ionic compound dissociates into its ions in gaseous state.


•`color{green}["Spontaneous process"]`: A process which under some given conditions may take place by itself or by initiation independent of the rate is called a spontaneous process.

•`color{green}["Non-Spontaneous process"]`: A process which can neither take place itself nor by initiation is called non- spontaneous process.

•`color{green}["Driving force"]`: The force which is responsible for the spontaneity of a process is called the driving force.

Is decrease in enthalpy a criterion for spontaneity?

Entropy and spontaneity

•`color{green}["Entropy"]`:Entropy is a measure of randomness or disorder of the system.

Gibbs energy and spontaneity

•`color{green}["Gibbs free energy"]`: Gibb's Free Energy. lt is defined as maximum amount of energy available to a system during the process that can be converted into useful work. It is a measure of capacity to do useful work.

•`color{green}["Second law of thermodynamics"]`The entropy of universe b continuously increasing due to spontaneous process taking place in it.