Thermodynamics_L1_2024 - Tagged

Thermal Dynamics Overview

  • Thermodynamics: The study of energy, heat, and work interrelationships. Fundamental laws govern energy conservation and transformation applicable to various systems (mechanical engines to biological processes).

Learning Outcomes

  • Understand fundamental thermodynamic concepts:

    • Thermodynamic systems, state functions, processes, and parameters.

  • Apply the Ideal Gas Law in gas-related problems.

  • Explain Raoult's Law and applications in solutions.

Key Concepts

Systems and Surroundings

  • System: The part of the universe being studied.

  • Surroundings: Everything outside the system.

State Functions

  • Properties like temperature, pressure, volume, and internal energy that define a system's state, dependent only on conditions, not the process used to get there. Common state functions include:

    • Enthalpy (H): Total heat at constant pressure.

    • Entropy (S): Measure of disorder.

    • Gibbs Free Energy (G): Available energy to do work.

Thermodynamic Processes

  • Transformations in a system characterized by changes in state functions due to heat transfer, work done, or variations in temperature and pressure.

Thermodynamic Systems

Types of Systems

  • Isolated System: No matter or energy exchange with surroundings.

  • Closed System: Energy exchange but no matter exchange.

  • Open System: Exchange of both energy and matter with surroundings.

Ideal Gas Law

  • Equation: PV = nRT

Variables Explained

  • P: Pressure (atm, Pa)

  • V: Volume (liters, cubic meters)

  • n: Amount of substance (in moles)

  • R: Universal gas constant (0.0821 L·atm/(K·mol) or 8.314 J/(K·mol))

  • T: Absolute temperature (Kelvin)

Assumptions and Limitations of Ideal Gas Law

Assumptions

  • Gases consist of many molecules in constant random motion.

  • Volume of gas molecules is negligible compared to the container volume.

  • No intermolecular forces except during elastic collisions.

Limitations

  • Most accurate at low pressures and high temperatures. Real gases deviate from ideal behavior under high pressure or low temperature.

Applications of Ideal Gas Law

  • Inhaler Formulations: Helps ensure proper propellant volume and pressure for medication delivery.

  • Gas Sterilization: Predicts how gas conditions affect sterilization efficacy.

  • Respiratory Gas Analysis: Aids in calculating gas partial pressures in blood samples.

  • Cell Culture: Maintains optimal atmospheric conditions for cell cultures.

Raoult’s Law

Vapor Pressure in Solutions

  • Vapor Pressure: The pressure of the vapor present above a liquid.

  • Raoult’s Law Equation: Psoln = Xsolvent Psolvent

    • Where, Psoln = observed vapor pressure of the solution, Xsolvent = mole fraction, Psolvent = vapor pressure of pure solvent.

  • The presence of a nonvolatile solute lowers the solvent's vapor pressure.

Ideal vs. Nonideal Solutions

  • Ideal Solutions: Obey Raoult’s Law where molecular interaction behavior is similar to pure components.

  • Negative Deviation: Strong interactions between different components lead to lower vapor pressures than predicted.

  • Positive Deviation: Weaker interactions lead to higher vapor pressures than predicted.

Practical Applications of Raoult's Law

  • Drug Formulation: Predicts excipient effects on the vapor pressure of active ingredients.

  • Solubility: Assesses drug solubility in solvents for dosage form development.

  • Biological Fluids: Studies vapor pressuring in biological systems.

Example Problems

Ideal Gas Law Example

  • Calculate volume for 500g of iodine:

    • Given: Temp = 300°C; Pressure = 740 mmHg.

    • Results in volume = 95.1 L.

Raoult’s Law Example

  • Dissolving 58.44 g of NaCl in 1 kg of water affects vapor pressure (from 23.76 mmHg to approximately 23.31 mmHg), demonstrating vapor pressure lowering due to solute presence.