CBSE Class 11th Chemistry Thermodynamics

The study of the relationship between heat (or energy) and work is known as thermodynamics. To put it another way, thermodynamics studies how energy may be added to a system (a machine or a molecule) to cause it to function. As an alternative, we might be able to modify a system such that it generates energy (e.g., by turning the turbines of a power plant to generate electricity).
In chemistry, we may refer to the "energetics" of reactions more widely than thermodynamics because energy released during a reaction might just evaporate into thin air without producing any meaningful work. However, the concepts remain the same: a group of molecules can undergo a reaction when energy is provided to them, or a reaction right.

Thermodynamic state and Applications:

• First Law of Thermodynamics
• Second Law of Thermodynamics
• Third Law of Thermodynamics
• Spontaneity, Gibbs Energy Change and Equilibrium

Energy changes in chemical or physical processes are the subject of thermodynamics, which allows us to analyze these changes statistically and generate insightful predictions. We split the cosmos into the system and its surroundings for these purposes.

The first law of thermodynamics: is also known as the energy conservation law. It states that energy is uncreated and unstoppable. Additionally, it says that an isolated system's energy is constant.Heat (q) is produced or absorbed by chemical or physical processes, some of which can be transformed into work (w).

The change in internal energy establishes the relationship between these values and the first law of thermodynamics. While q and w depend on the path and are not state functions, they solely depend on the beginning and final states.When these numbers are added to the system, we give them the positive sign that is consistent with the sign standards of q and w. The heat transfer that results in temperature changes between systems can be measured.
The magnitude of the rise in temperature depends on the heat capacity (C) of a substance. Therefore, heat absorbed or evolved is q = CDT.  Work can be measured by w = – in the case of the expansion of gases.
Work done in isothermal and reversible expansion of ideal gas.Wrev, is measured by using a special calorimeter called a bomb calorimeter.
A system's enthalpy can be expressed as the total internal energy plus the product of its volume and pressure. It can be expressed as H = U + PV and is represented by the symbol H.
A property that is extensive is one whose value is contingent upon the amount or volume of materials contained within the system. Enthalpy, mass, heat capacity, volume, internal energy, etc. are a few examples.
A property that is intense is one whose value is independent of the amount or size of matter in the system. Pressure, density, temperature, and so on are examples.
The amount of heat needed to raise the temperature of one unit mass of a substance by one degree Celsius (or one Kelvin) is known as specific heat, also known as specific heat capacity.
The following is the relationship between the specific heat of a substance (c), the quantity of heat (q) needed to raise a sample's temperature, and the change in temperature:
At constant pressure, the enthalpy change can be simply calculated from the changes in heat. 
Different enthalpy changes exist. Phase transitions, including melting, vaporization, and sublimation, often take place at constant temperature and are identified by consistently positive enthalpy changes.
The reaction enthalpy () is the enthalpy change that results from a reaction and is calculated as follows: = (sum of enthalpies of products) – (sum of enthalpies of reactants).
A thermochemical equation is a balanced chemical equation that includes its value. 
The enthalpy of formation, combustion, and other enthalpy changes can be calculated using Hess’s law.

Hess’s Law of Constant Heat Summation states:
The total of the standard enthalpies of the intermediate reactions into which the entire reaction may be split at the same temperature is the standard reaction enthalpy of a reaction that occurs in multiple steps.enthalpy change for chemical reactions can be determined byAnd in gaseous state,

bond enthalpies of the reactants and the bond enthalpies of the products.
The direction of chemical reactions—that is, the power behind a chemical reaction—is not something that the first law of thermodynamics tells us. DU = 0 for isolated systems.

Born-Haber Cycle: is utilized to calculate the lattice enthalpy of ionic compounds because direct experimentation is not possible to determine them.The enthalpy change that happens when one mole of an ionic compound dissociates into its ions in a gaseous state is known as the lattice enthalpy of an ionic compound.For this aim, we define another state function, S, entropy.
According to the Second Law of Thermodynamics, spontaneous processes inside the cosmos cause its entropy to continuously increase.

Entropy (S): A measure of disorder or unpredictability is called entropy (S). Total entropy change is positive for a spontaneous change. Entropy change, as opposed to energy change, is what identifies a spontaneous change in an isolated system when DU = 0 and DS > 0. Equations can be used to quantify changes in entropy.
 for a reversible process.  is independent of the path.

Gibbs energy: G, which is connected to the system's enthalpy and entropy changes by the following equation. For a spontaneous change and at equilibrium. If the process is non-spontaneous,. The equilibrium constant is connected to the standard Gibbs energy change by this equation, which can be used to compute K if we know where it can be found. An essential component of the equation is temperature. For systems with positive reaction entropy, many reactions that are non-spontaneous at low temperatures become spontaneous at high temperatures.

FAQ-

Q. What is thermodynamics?
Ans. Thermodynamics is the branch of physics that deals with the relationships between heat, work, and energy. It describes how energy transfers and transforms during physical and chemical processes.

Q. What are the laws of thermodynamics?
Ans, The four laws of thermodynamics govern energy transfer and transformation.

• The Zeroth Law: If two systems are in thermal equilibrium with a third system, they are in equilibrium with each other.

• The First Law: Energy cannot be created or destroyed, only be transferred or transformed.

• The Second Law: The entropy of a closed system tends to increase over time.

• The Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum value.

Q. What is entropy?
Ans. Entropy is a measure of the disorder or randomness of a system. It increases in a closed system over time, according to the Second Law of Thermodynamics.

Q. What is the significance of thermodynamic equilibrium?
Ans. Thermodynamic equilibrium occurs when a system's properties no longer change with time. It is a state of maximum entropy and minimum free energy, crucial for understanding the behavior of systems in various conditions.

Q. How does thermodynamics relate to chemical reactions?
Ans. Thermodynamics governs the energy changes that occur during chemical reactions. Reactions that release energy are exothermic, while those that absorb energy are endothermic, and both can be analyzed using thermodynamic principles.