Thermodynamics Overview Quiz

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Questions and Answers

What is the primary focus of thermodynamics?

  • The physical characteristics of matter
  • The chemical composition of substances
  • The interaction of a body with its surroundings involving energy transfer (correct)
  • The properties of different chemical bonds

Which type of system can exchange energy and matter?

  • Isolated System
  • Equilibrium System
  • Open System (correct)
  • Closed System

Which of the following properties depend on the size of the system?

  • Heat Capacity (C) (correct)
  • Pressure (P)
  • Temperature (T)
  • Color

What occurs during bond breaking?

<p>Energy is absorbed (A)</p> Signup and view all the answers

In terms of sign convention, when is heat (q) considered positive?

<p>When heat is absorbed (B)</p> Signup and view all the answers

What is the relationship between change in enthalpy and change in internal energy for a constant process?

<p>$ riangle H = riangle U + P riangle V$ (B)</p> Signup and view all the answers

In a free expansion of a gas, what is the change in entropy of the system?

<p>$ riangle S_{sys} = 0$ (B)</p> Signup and view all the answers

What is the molar heat capacity at constant pressure for an ideal gas?

<p>$C_p = rac{5}{2}R$ (D)</p> Signup and view all the answers

According to the second law of thermodynamics, what is the entropy change in an isolated system?

<p>$ riangle S_{universe} &gt; 0$ (D)</p> Signup and view all the answers

Which of the following statements about entropy is true?

<p>Entropy order follows Gas &gt; Liquid &gt; Solid. (A)</p> Signup and view all the answers

What best describes internal energy (U)?

<p>Sum of all types of energy including chemical and mechanical (D)</p> Signup and view all the answers

In a reversible process, which of the following is true?

<p>Changes can be reversed and equilibrium is assumed (D)</p> Signup and view all the answers

Which process type represents constant temperature?

<p>Isothermal Process (D)</p> Signup and view all the answers

According to the first law of thermodynamics, what is the correct equation for the change in internal energy?

<p>ΔU = Q - W (C)</p> Signup and view all the answers

What does the Zeroth Law of Thermodynamics state?

<p>If two bodies are in thermal equilibrium with a third, they are in equilibrium with each other (D)</p> Signup and view all the answers

What is the formula for the change in entropy for an ideal gas?

<p>$ Delta S = nR rac{T_2}{T_1} + nR rac{V_2}{V_1}$ (B)</p> Signup and view all the answers

Which statement characterizes a spontaneous process?

<p>$ Delta G &lt; 0$ and $ Delta S &gt; 0$ (C)</p> Signup and view all the answers

What is the entropy change during the fusion process described by the equation?

<p>$ Delta S_{fusion} = rac{ Delta H_{fusion}}{T}$ (C)</p> Signup and view all the answers

At equilibrium conditions, which statement is true?

<p>$ Delta G = 0$ and $K = 1$ (D)</p> Signup and view all the answers

How is the change in Gibbs Free Energy related to the electrical energy generated in a cell?

<p>$ Delta G = -nFE_{cell}$ (A)</p> Signup and view all the answers

What is the relationship expressed by the universal ratio between specific heat capacities?

<p>$\frac{C_p}{C_v} = \gamma$ (B)</p> Signup and view all the answers

In an isothermal process, what remains constant throughout the process?

<p>Temperature (A)</p> Signup and view all the answers

What happens to the internal energy ($\Delta U$) during an adiabatic process in an ideal gas?

<p>$\Delta U = nC_v\Delta T$ (B)</p> Signup and view all the answers

What does a positive change in enthalpy ($\Delta H > 0$) indicate about the reaction?

<p>It is endothermic (D)</p> Signup and view all the answers

How is work done ($W$) calculated in an adiabatic process?

<p>$W = P_{ ext{ext}}\Delta V$ (D)</p> Signup and view all the answers

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Study Notes

Thermodynamics

  • Branch of science that studies the interactions of a body with its surroundings, involving energy transfer.
  • Key concepts include bond breaking (endothermic) and bond formation (exothermic).

Universe

  • Consists of a system, surroundings, and a boundary separating them.

System

  • Part of the universe under observation.

Surroundings

  • Everything outside the system.

Boundary

  • Anything that separates the system and its surroundings.

Types of Systems

  • Open system: Exchanges both energy and matter with its surroundings.
  • Closed system: Exchanges energy but not matter with its surroundings.
  • Isolated system: Exchanges neither energy nor matter with its surroundings.

State Functions

  • Depend on the initial and final state of the system.
  • Key examples include:
    • Change in internal energy (ΔU)
    • Change in enthalpy (ΔH)
    • Change in entropy (ΔS)
    • Change in Gibbs free energy (ΔG)
    • Pressure (P)
    • Temperature (T)
    • Volume (V)
  • Work:
    • Work done by the system is negative.
    • Work done on the system is positive.

Units

  • 1 calorie (cal) = 4.2 Joules (J)
  • 1 liter-atmosphere (L·atm) = 101.3 J
  • 1 atmosphere (atm) = 100 kilopascals (kPa)

Properties

  • Extensive properties: Depend on the size of the system.
    • Examples include: Volume (V), Enthalpy (H), Internal Energy (U), Heat Capacity (C)
  • Intensive properties: Independent of the size of the system.

Golden Rule

  • Extensive property: Dependent on size.
  • Intensive property: Independent of size.

Heat (q)

  • Energy transferred due to temperature differences between the system and surroundings.

Sign Convention

  • Heat (q)
    • Positive: Heat is absorbed by the system.
    • Negative: Heat is released by the system.
  • Work (w)
    • Positive: Work is done on the system.
    • Negative: Work is done by the system.

Entropy Change for an Ideal Gas

  • Formula: ΔS = nR ln(T2/T1) + nR ln(V2/V1)

Types of Processes

  • Reversible Process
    • Isothermal: ΔS = nR ln(T2/T1)
    • Adiabatic: ΔS = 0
  • Entropy Change During Phase Transformation
    • Fusion: ΔS = ΔH / T
    • Vaporization: ΔS = ΔH/ T
  • Entropy Change in Chemical Reactions
    • ΔS = S(products) - S(reactants)

Spontaneous vs Non-Spontaneous Processes

  • Spontaneous Process
    • Conditions:
      • ΔG < 0 (Gibbs Free Energy)
      • ΔS > 0 (Entropy)
  • Non-Spontaneous Process
    • Conditions:
      • ΔG > 0
      • ΔS < 0

Super Notes

  • Relationship between ΔG, ΔS, and ΔH:
    • ΔG = ΔH - TΔS
    • ΔG = ΔG° + RT ln(Q) (Standard Free Energy Change at 298K)
  • Equilibrium Condition:
    • ΔG = 0
    • K = e^(-ΔG°/RT)
  • Work (Non-expansion work) Description:
    • ΔG = -ΔEcell
  • Electrical Energy:
    • ΔG = -nFEcell

Key Concepts

  • For constant pressure:
    • ΔH = ΔU + PΔV
  • For Ideal Gas:
    • PV = nRT

Free Expansion

  • Always leads to irreversible states.
  • ΔSsys = 0

Heat Capacity

  • At constant volume (Cv):
    • Cv = 2/3R
  • At constant pressure (Cp):
    • Cp = 5/2R

Limitations of Joule-Thomson Effect

  • It doesn't explain the elasticity of a process under given conditions.

Entropy (S)

  • Measure of the degree of randomness or disorder of a system.
  • Relationship: ΔS = Qrev/T

Unit of Entropy

  • J/K·mol

Entropy Change in Isolated System

  • Laws:
    • ΔSuniverse > 0
    • ΔSsystem + ΔSsurroundings = 0

Entropy Order

  • Gas > Liquid > Solid

Thermodynamic Processes

  • Isothermal Process
    • Constant temperature: ΔT = 0
    • Formula: W = nR(T1 - T2)
  • Adiabatic Process
    • Constant heat: ΔQ = 0
    • Formula: PV^γ = Constant
    • Formula: TV^(γ-1) = Constant
  • Isochoric Process
    • Constant volume: ΔV = 0
    • Formula: W = 0
  • Isobaric Process
    • Constant pressure: ΔP = 0

Key Concepts

  • Metric Ratio:
    • Cp - Cv = R for 1 mole
    • Cp - Cv = R for various moles
  • Universal Ratio:
    • Cp/Cv = γ

Work Done in Adiabatic Process

  • Formula: W = PextΔV = -ΔnRT
  • Formula: ΔU = nCvΔT

Specific Heat Capacities and Values

Type Symbol Value
Monatomic Cv 3/2R
Diatomic Cv 5/2R
Triatomic Cv Linear: 5/2R Non-Linear: 3/2R

Enthalpy and Heat Transfer

  • Formula: ΔH = ΔU + P(V2 - V1)
  • Endothermic: ΔH > 0
  • Exothermic: ΔH < 0

Internal Energy (U)

  • Sum of all types of energy (chemical, electrical, mechanical, etc.).
  • Changes with temperature.

States of Thermodynamics

  • At constant volume, only temperature affects internal energy (U).

Types of Processes

  • Reversible process
    • Slow, reversible changes.
    • Equilibrium assumed at all stages.
    • Usable path.
  • Irreversible process
    • Fast, irreversible changes.
    • No equilibrium reached.
    • Constant path.
    • Natural processes.

Thermodynamic Processes

  1. Isothermal: ΔT = 0
  2. Isochoric: ΔP = 0
  3. Isobaric: ΔV = 0
  4. Adiabatic: ΔQ = 0

Cycle Process

  • Initial state = final state
  • ΔE = ΔH = 0

Translation to Change in Functions

  • Cycle process: ΔE = ΔH = 0

Zeroth Law of Thermodynamics

  • If two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other.

First Law of Thermodynamics

  • Based on conservation of energy.
  • Energy can be transformed from one form to another.
  • Change in internal energy is constant.

Mathematical Expression

  • ΔU = Q - W

Types of Thermodynamic Processes

  • Reversible Isothermal Process: PV = nRT

Important Formulas

  • W = -nRT ln(Vf/Vi)

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