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Questions and Answers
What characterizes an isothermal process?
What characterizes an isothermal process?
Which of the following describes a cyclic process?
Which of the following describes a cyclic process?
What is a nonspontaneous process?
What is a nonspontaneous process?
Which of the following statements is true about spontaneous processes?
Which of the following statements is true about spontaneous processes?
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What describes an adiabatic process?
What describes an adiabatic process?
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What does the symbol ΔH represent in thermodynamics?
What does the symbol ΔH represent in thermodynamics?
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Under what condition is ΔH equal to qp?
Under what condition is ΔH equal to qp?
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What indicates an endothermic reaction in terms of ΔH?
What indicates an endothermic reaction in terms of ΔH?
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Which equation accurately describes the change in enthalpy for a gas expanding at constant pressure?
Which equation accurately describes the change in enthalpy for a gas expanding at constant pressure?
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During reversible expansion of an ideal gas, what condition must be true regarding the external and internal pressures?
During reversible expansion of an ideal gas, what condition must be true regarding the external and internal pressures?
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Study Notes
Properties of Matter
- Extensive Properties: Additive properties such as mass, volume, and internal energy.
- Intensive Properties: Non-additive properties that do not change regardless of the amount.
Types of Thermodynamic Processes
- Isothermal Process: Temperature remains constant (dT = 0).
- Adiabatic Process: No heat exchange with surroundings (dq = 0).
- Isobaric Process: Occurs at constant pressure (dP = 0).
- Isochoric Process: Volume remains constant (dV = 0).
- Cyclic Process: System returns to initial state after a series of processes (dE = 0, dH = 0).
Spontaneous and Nonspontaneous Processes
- Spontaneous Process: Proceeds naturally without external effort.
- Nonspontaneous Process: Requires energy to proceed, thus not occurring on its own.
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Criteria for Spontaneity:
- Unidirectional change; reverse requires work.
- Time is irrelevant; change can be rapid or slow.
- Unstable systems lead to inevitable spontaneous changes.
- Systems at equilibrium do not change without disturbance.
Enthalpy
- Definition: Enthalpy (H) is the sum of internal energy (E) and the product of pressure (P) and volume (V).
- Mathematical Expression: H = E + PV
- Change in Enthalpy: ΔH = H2 - H1; can be expressed as ΔH = (ΔE) + (ΔPV).
- Relationship with Heat: At constant pressure, ΔH equals the heat transferred (qp).
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Sign Conventions:
- ΔH positive indicates endothermic reaction.
- ΔH negative indicates exothermic reaction.
Reversible Expansion
- Involves infinitesimal steps where pressure is adjusted, allowing for controlled expansion.
- Defined by the process with no appreciable external resistance.
Heat Capacity
- At Constant Pressure (Cp): The rate of change of enthalpy with temperature.
- At Constant Volume (CV): Similar definition focusing on internal energy.
- Relation: Cp = CV + R, where R is the ideal gas constant.
Second Law of Thermodynamics & Entropy
- Spontaneous processes lead to an increase in the total entropy of the universe (ΔSuniverse > 0).
- For reversible processes, the entropy (ΔSuniverse = 0) remains constant.
- Definition of Entropy: Measures the disorder or randomness of a system's molecules.
Example Calculation
- Heat of formation for potassium hydroxide (KOH) calculated from given reactions results in ΔH = -102.5 kcal.
- Another reaction involved is C(s) + 2H2(g) → CH4(g) with ΔH calculated to be -74.8 kJ.
Concept Check Questions
- Assess understanding of systems: isolated, closed, open.
- Identify work done during gas expansion against pressure.
- Evaluate the correctness of statements related to properties of heat and enthalpy.
Answers to Concept Questions
- Thermos flask is an isolated system.
- Zinc and acid reaction is an open system.
- Work done by the gas in expansion is -100 lit atm.
- Heat is not a state function, so the respective statement is not correct.
- Enthalpy change is independent of nature and state of the reactants and products.
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Description
Explore the concepts of extensive and intensive properties in thermodynamics, including isothermal, adiabatic, and isobaric processes. This quiz will test your understanding of the fundamental principles that govern thermodynamic systems. Dive into the intricacies of energy transfer and state properties.
