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Questions and Answers
The total work done is the summation of all the ______ terms.
PdV
At constant volume, ΔV = 0, so ΔU = ______.
qv
Enthalpy is defined as H = U + ______.
PV
The change in enthalpy equals the heat transferred at constant ______.
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Heat lost from the system to surroundings is an ______ process.
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Intensive properties are ______ of the size of the system.
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Extensive properties, such as internal energy, are ______ on the size of the system.
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ΔU and ΔH are thermodynamic ______ functions.
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The cylinder will leak if the pressure exceeds ______ Pa.
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The molecular mass of oxygen (O2) is ______ g mol−1.
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The equation relating pressure, volume, and temperature for gases is ______.
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Heat transferred to/from the system is quantified by ______.
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Work done on the system is quantified by ______.
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The first law of thermodynamics states that energy can neither be ______ nor destroyed.
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The change in enthalpy is represented by Δ______.
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For an ideal gas, internal energy is constant when the system is ______.
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Heat flows from a hotter body to a colder body, not ______ versa.
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In the equation ΔU = ______ + w, 'ΔU' represents the change in internal energy.
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Energy associated with translational, rotational, and vibrational motion is part of the internal ______ of an ideal gas.
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Entropy (S) measures the degree of disorder or ______ of a system.
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A spontaneous process occurs in one ______.
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In an expansion at constant pressure, the work done by the system is ______.
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To predict the position of equilibrium, we need ΔH and also the direction of spontaneous ______.
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Higher entropy indicates greater disorder and lower ______ indicates greater order.
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The change in entropy (ΔS) is a key parameter for determining the direction of ______ change.
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Gas molecules mix randomly when partition is removed, but the ______ process is not observed spontaneously.
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In thermodynamics, entropy is considered a state ______.
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As temperature decreases, entropy ______ decreases.
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At 0 ◦C, ice and water are in __________.
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The enthalpy of melting for ice, ΔHmelting, is __________ kJ mol−1.
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For a reversible process, ∆S is defined as __________ over temperature.
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The second law of thermodynamics states that in a spontaneous process, __________ of the universe increases.
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During an irreversible process, the change in entropy is __________ than in a reversible process.
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Entropy decreases with decreasing ______.
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Entropy is a thermodynamic state ______ function.
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The change in entropy (ΔS) for a particular ______ is independent of path.
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The 3rd Law of Thermodynamics states that S at 0 K = ______ J mol−1 K−1.
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Heat (q) can be expressed as an intensity factor multiplied by a ______ factor.
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For a given process, the change in entropy is given by ΔS = q / ______.
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A spontaneous process occurs in a system that is not at ______.
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A reversible process occurs when the system and surroundings are at ______.
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An irreversible process continues until ______ is reached.
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In thermodynamics, the intensity factor for mechanical energy can be ______ or pressure.
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Study Notes
Expansion of Gases
- Work is done by the system when gas expands from volume Vi to Vf at constant pressure P.
- Work done is calculated as the product of pressure and change in volume.
- Total work done is the summation of all PdV terms.
Internal Energy
- The change in internal energy (ΔU) is equal to the heat (q) absorbed by the system plus the work (w) done on the system: ΔU = q + w.
- At constant volume, ΔU = qv. (qv implies constant volume).
- At constant pressure, ΔU = qp - PΔV. (qp implies constant pressure).
Enthalpy
- Enthalpy (H) is a new energy function defined as H = U + PV.
- The change in enthalpy (ΔH) equals the heat transferred at constant pressure (ΔH = qp).
Thermochemistry
- Thermochemistry examines heat transfers (enthalpy changes) during various processes, including melting, binding, dilution, and reaction.
- Examples include enthalpy of fusion, enthalpy of binding, and enthalpy of formation.
- Enthalpy of formation (ΔHf) is the heat absorbed at constant pressure when one mole of a compound is formed from its elements in their most stable forms.
- ΔHf⁰ is the enthalpy of formation at 25°C and 1 atmosphere pressure.
- Exothermic processes release heat (ΔH -ve), while endothermic processes absorb heat (ΔH +ve).
Thermodynamic State Functions
- Thermodynamic state functions depend only on the present condition (state) of the system, not its history.
- ΔU and ΔH are thermodynamic state functions.
- Work (w) and heat (q) are not state functions.
Intensive vs. Extensive Properties
- Intensive properties are independent of the size of the system, such as pressure (P) and temperature (T).
- Extensive properties depend on the size of the system, such as internal energy (U) and enthalpy (H).
First Law of Thermodynamics
- States that energy cannot be created or destroyed.
- The internal energy (U) of an isolated system remains constant.
- Changes to the internal energy of a system can occur through heat transfer or work being done on/by the system.
Changes to Internal Energy
- ΔUsystem + ΔUsurroundings = 0.
- ΔUsystem = - ΔUsurroundings.
Heat and Work
- Heat (q) is energy transferred between a system and its surroundings due to temperature differences.
- Work (w) is energy transferred capable of lifting a weight.
Relating Work (w) to P and V
- Work done by the system is negative during expansion.
Direction of Spontaneous Change
- The first law of thermodynamics describes the energy balance but not the direction of a process.
- To predict equilibrium position, both ΔH and the direction of a spontaneous change are required.
Spontaneous Processes
- Many processes only occur in one direction, such as heat flowing from a hotter body to a colder one.
Entropy
- Entropy (S) measures the disorder or randomness of a system.
- Higher entropy indicates greater disorder.
- Entropy is a thermodynamic state function.
- The change in entropy (ΔS) determines the direction of a spontaneous process.
Energy and Temperature, Heat, and Entropy
- Energy can be expressed as an intensity factor multiplied by a capacity factor.
- The intensity factor is the driving force, while the capacity factor is the extent over which the force is conveyed.
- Heat can be expressed as temperature (T) multiplied by entropy (S): q = T × S.
- For a given process, ΔS = q/T.
Reversible and Irreversible Processes
- Spontaneous processes are not at equilibrium.
- Irreversible processes continue until equilibrium is reached.
- Reversible processes occur at dynamic equilibrium.
Reversible Transfer of Heat
- An example is ice and water at equilibrium at 0°C.
- Heat gained by the ice equals heat lost by water, resulting in no overall change in entropy of the universe.
Irreversible Transfer of Heat
- Heat transfer from a hot object to a cold object results in an increase in the entropy of the universe.
Second Law of Thermodynamics
- States that the entropy of the universe increases during spontaneous processes.
- ΔS ≥ q/T.
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Description
Explore the key concepts of thermodynamics, including gas expansion, internal energy, and enthalpy. This quiz covers the formulas and principles governing heat transfer and work done throughout various thermodynamic processes. Test your understanding of these fundamental topics!
