Thermodynamics | Chemical & Ionic 🔥 Oneshot | NCERT PYQs| NEET 2024 | Diksha Ma'am

Vedantu NEET English・2 minutes read

Vidant English with Dsha Kel is covering physical chemistry basics in-depth, emphasizing the importance of thermodynamics and sign conventions, aiming to complete the syllabus in 10 days. Topics include state functions, heat capacities, thermodynamic laws, and spontaneous processes, all crucial for understanding chemical reactions and energy changes.

Insights

Physical chemistry topics covered include thermodynamics, chemical equilibrium, and ionic equilibrium, emphasizing the importance of studying thermodynamics for exams and its connection to physics.
Sign conventions in chemistry and physics, understanding work done formulas, and focusing on clarity in concepts are urged for students by Vidant English with Dsha Kel.
State functions and path functions are defined, with detailed explanations on thermodynamic processes like isothermal, isobaric, isochoric, adiabatic, and cyclic processes.
The first and second laws of thermodynamics, along with the zeroth law, are explained, emphasizing the importance of energy conservation and thermal equilibrium.
Concepts like entropy, Gibbs free energy, spontaneity of reactions, and the relationship between Delta G, Delta H, and Delta S are crucial in determining the feasibility and direction of chemical processes.

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What is thermodynamics in chemistry?
The study of heat and energy transfer.

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Summary

00:00

Mastering Thermodynamics: Chemistry's Crucial Concepts Explained

Vidant English with Dsha Kel, a Chemistry Master teacher, is starting physical chemistry, covering basic concepts like structure of atom, thermodynamics, chemical equilibrium, and ionic equilibrium.
Emphasizes the importance of studying thermodynamics and not skipping it, as it's crucial for exams and connects to physics.
Thermodynamics and thermochemistry are being covered in detail in the current session.
Urges students to focus on sign conventions in chemistry and physics, along with understanding work done formulas.
Promises to complete the syllabus within 10 days, stressing the importance of dedication and consistency.
Defines thermodynamics as the study of heat and energy transfer during chemical and physical changes.
Explains the terms Universe, system, surroundings, and boundary in relation to observations and differentiation.
Details open, closed, and isolated systems, highlighting the exchange of mass and energy in each.
Discusses extensive and intensive properties, clarifying that the division of two extensive properties results in an intensive property.
Compares heat capacity, specific heat capacity, and molar heat capacity, noting the dependence on mass for heat capacity and the independence for specific and molar heat capacities.

18:44

Thermodynamics: State vs. Path Functions

Melting point and boiling point are fixed for any substance, independent of mass.
Basic terminologies include State function and path function.
State function is independent of the path followed, while path function depends on the path.
Work and heat are path functions, while enthalpy, entropy, internal energy, and free energy are state functions.
Thermodynamic processes include isothermal, isobaric, isochoric, adiabatic, and cyclic processes.
In a cyclic process, all state functions have zero values.
Internal energy is the combined energy of a system, including kinetic, potential, vibrational, and rotational energies.
Internal energy change (delta U) is calculated as final U minus initial U.
Heat is energy transfer due to temperature differences, while work is any energy transfer not involving heat.
Work done on the system is positive, while work done by the system is negative.

35:47

Thermodynamics: State vs. Path Functions

State functions are not dependent on the path, including Delta S, Delta G, Delta U, and Delta H.
Path functions, like heat and work, are dependent on the path.
Q + W equals Delta U, making it a state function.
The answer to the question is the second and third options.
The zeroth law of thermodynamics states that if A is in thermal equilibrium with B and B is in thermal equilibrium with C, then A is in thermal equilibrium with C.
The first law of thermodynamics states that energy can neither be created nor destroyed, only converted.
The formula for the first law of thermodynamics is Delta U = Q + W.
Work done is equal to -P DV in the first law of thermodynamics.
Graphs for isobaric, isochoric, and isothermal processes show the relationships between pressure, volume, and temperature.
For adiabatic processes, where there is no heat exchange, internal energy and work done are positive.

53:40

Understanding Adiabatic and Cyclic Processes in Thermodynamics

Adiabatic process involves two formulas: reversible and irreversible.
Work done in adiabatic process is represented as minus P.
Work should be positive in adiabatic process.
Cyclic process has zero state functions, making Delta U zero.
Isochoric process has zero volume change, resulting in zero work done.
Heat energy change at constant volume is denoted as QV.
Isobaric process involves enthalpy change, with QP equal to Delta H.
In a closed insulated container, heat change is zero.
Reversible processes involve infinite steps, while irreversible processes involve a single big change.
Reversible processes are carried out slowly to maintain equilibrium, while irreversible processes are fast and irreversible.

01:12:04

"Understanding Reversible and Irreversible Processes in Thermodynamics"

Studying for one or two days is reversible, while irreversible processes are those that complete in finite times.
In compression, Delta U and Delta V are negative, indicating a decrease in final volume.
Work done on the system is positive during compression and negative during expansion.
For reversible processes, work done is calculated as integration of -PdV in very small steps.
For irreversible processes, work done is calculated as -P Delta V for large changes.
External pressure is used for irreversible processes due to significant changes.
Reversible processes involve infinite steps with small changes, while irreversible processes have finite steps with large changes.
Work done in expansion is more in reversible processes and less in irreversible processes, while in compression, it's the opposite.
Isothermal processes have constant temperature, leading to Delta U and Delta H being zero.
Work in isothermal processes is calculated using the formula PdV = nRT ln(V2/V1) for reversible processes.

01:30:18

Logarithmic formula for volume and pressure calculations

Logarithmic formula: Use 2.303 log B to 10 for calculations.
Logarithmic rule: In log, final volume is divided by initial volume, and initial pressure is divided by final pressure.
Volume calculation: V2 divided by V1, Pressure calculation: P1 divided by P2.
Irreversible process: Use Delta instead of integration, Delta U is zero.
Work calculation for irreversible process: Use Delta, work equals -V2 - V1.
Ideal gas equation: Use P nRT, convert to -P2 - 1/P1 for work calculation.
Isocoric process: Work is -P DV, QV equals Delta U.
Isobaric process: Work is -P external DV for reversible process, integrate for value.
Cyclic process: Work equals area covered, positive for clockwise, negative for anticlockwise.
Heat capacity definition: Heat required to raise temperature by 1°C.
Heat capacity formulas: Include heat capacity, molar heat capacity, specific heat capacity, at constant pressure and volume, and their respective calculations.

01:49:51

Understanding Molar Heat Capacity in Thermodynamics

Molar heat capacity is a crucial concept in thermodynamics.
The relation CP minus CV equals R is correct when considering one mole.
It's essential to multiply by the number of moles if not explicitly stated.
Poisson's ratio, represented by gamma, is CP divided by CV.
Formulas for calculating CV in terms of gamma are provided.
Different gases have varying degrees of freedom affecting their heat capacities.
Monatomic gases have three degrees of freedom, diatomic linear gases have five, and nonlinear polyatomic gases have six.
The value of gamma for different gases is determined by their degrees of freedom.
The value of gamma for monatomic gases is 1.67.
Adiabatic processes involve no heat exchange, with temperature changes indicating cooling or heating.

02:08:19

Thermodynamics: Heat, Energy, and Entropy Explained

Total heat change in isobaric conditions with constant pressure is denoted as QP.
Total heat energy change in isobaric conditions is equal to QP, while in constant volume conditions, it is equal to QB.
The formula for internal energy representation at constant pressure is Delta U = QP - P Delta V.
Free expansion occurs when external pressure is zero, resulting in zero work done, heat energy, and internal energy change.
Enthalpy represents the total heat content of a system, calculated as Delta H = QP - P Delta V.
Enthalpy change at constant pressure is represented as Delta H = Delta U + P Delta V.
Q is a path function, while P and V are state functions, with Delta H being independent of the path.
Delta G is negative for spontaneous processes and positive for non-spontaneous processes.
Entropy measures the disorder of a system, with Delta S = Q reversible / T being the formula.
Entropy increases with temperature, volume in gases, complexity, and molar mass in gaseous substances.

02:27:17

Entropy Changes and Spontaneous Processes in Chemistry

Denaturation, desolution, mixing, rusting of iron, and crystallization lead to changes in entropy, with some causing an increase and others a decrease.
An increase in the number of gas molecules during a chemical reaction results in an increase in entropy due to increased randomness.
The relationship between the change in the number of gaseous moles (Delta NG) and entropy (S) determines whether entropy is positive or negative.
The magnitude of entropy change is represented by the formula Delta S = Products - Reactants.
The second law of Thermodynamics states that heat cannot move from a low to high-temperature body, and processes must involve the absorption of heat.
Spontaneous processes are irreversible without external energy, and the entropy of the universe increases in spontaneous processes.
Entropy is maximum at equilibrium, with the change in entropy (Delta S) being zero at equilibrium.
Spontaneous processes have positive total entropy, while non-spontaneous processes have negative total entropy.
The calculation of Delta surroundings involves the formula Delta S surroundings = -Q system / T, with Q surroundings being -Q system.
Gibbs free energy (Delta G) determines the spontaneity of a process, with negative Delta G indicating spontaneity and positive Delta G indicating non-spontaneity.

02:46:42

Thermodynamics and Enthalpy in Chemical Reactions

For a spontaneous reaction where Delta H and Delta S do not change with temperature, Delta G will be less than zero, indicating spontaneity.
To find the temperature where Delta G is less than zero, use the Gibbs equation and equate T to Delta H divided by Delta S, resulting in a temperature greater than 425 K.
The third law of thermodynamics states that the entropy of a perfectly crystalline solid is zero at Absolute Zero, an imaginary concept.
Standard conditions for enthalpy changes are at 25°C and 1 atm pressure, represented by Delta H, Delta G, and Delta S.
Hess's Law states that the total enthalpy change in a reaction is constant regardless of the intermediate steps taken, as enthalpy change is a state function.
To calculate the standard heat of formation of carbon disulfide, multiply and divide the given enthalpy changes for carbon, sulfur, and carbon disulfide.
Enthalpy of neutralization is constant for strong acid and base combinations, while bond enthalpy is the heat required to break one mole of bonds, always calculated as reactants minus products.
Enthalpy of dissolution is the heat released or absorbed when a substance is diluted, while heat of formation is the heat evolved when one mole of a substance is obtained from its elementary state.
Enthalpy of combustion is the heat change when one mole of a substance undergoes complete combustion, always considering one mole of the main reactant.
Calorific values represent the amount of heat released when a substance is combusted, crucial for understanding energy changes in chemical reactions.

03:04:38

Chemical Thermodynamics and Reaction Spontaneity

Caloric value is determined by the heat of combustion divided by the molecular mass of the substance.
The relationship between Gibbs free energy, entropy, and enthalpy is expressed through an equation.
The spontaneity of a reaction is indicated by a negative Delta G value.
Enthalpy change for a reaction is calculated by subtracting the heat of formation of reactants from products.
Combustion of carbon forms CO and CO2, with specific heat of formation values provided.
The heat of combustion of CO is determined by subtracting the enthalpy changes of CO2 and O2.
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