p.3
State Functions and Internal Energy
How is the state of a thermodynamic system simpler than that in mechanics?
It does not require detailed knowledge of the motion of each particle; instead, it deals with average measurable properties.
p.3
State Functions and Internal Energy
What can cause a change in internal energy of a system?
Heat transfer, work done on or by the system, or matter entering or leaving the system.
p.1
Extensive and Intensive Properties
What is the difference between extensive and intensive properties?
Extensive properties depend on the amount of substance, while intensive properties do not.
p.4
Work, Heat, and the First Law of Thermodynamics
What is the effect of doing mechanical work on a system in terms of temperature change?
Doing mechanical work increases the temperature of the system, as shown by the change from temperature T_A to T_B.
p.10
Heat Capacity and Measurement Techniques
How is the heat (q) required to raise the temperature of a sample calculated?
By multiplying the specific heat (c) of the substance by the mass (m) and the change in temperature (∆T).
p.3
State Functions and Internal Energy
What properties must be specified to describe the state of a system?
Pressure (p), volume (V), temperature (T), and composition.
p.1
Laws of Thermodynamics
What is the first law of thermodynamics concerning?
The conservation of energy and its mathematical expression.
p.8
Work, Heat, and the First Law of Thermodynamics
What is the relationship between ∆H and ∆U at constant volume?
∆H = ∆U = qV when ∆V = 0.
p.9
Heat Capacity and Measurement Techniques
How is heat transferred to a system measured?
By monitoring the temperature rise, where q = C ∆T.
p.11
Enthalpy and Its Applications
What is the definition of ∆H in the context of calorimetry?
∆H is the heat absorbed or evolved at constant pressure, also known as the heat of reaction or enthalpy of reaction, ∆rH.
p.14
Enthalpy and Its Applications
What is the reference state of an element?
Its most stable state of aggregation at 25°C and 1 bar pressure.
p.1
Energy Transformations in Chemical Reactions
How can chemical energy be utilized apart from releasing heat?
It can do mechanical work or provide electrical energy.
p.1
Laws of Thermodynamics
When do the laws of thermodynamics apply?
When a system is in equilibrium or moves between equilibrium states.
p.6
Laws of Thermodynamics
What defines a reversible process?
A reversible process is one that can be reversed by an infinitesimal change and proceeds through a series of equilibrium states.
p.8
Energy Transformations in Chemical Reactions
What is true about ∆H in endothermic reactions?
∆H is positive for endothermic reactions which absorb heat.
p.3
Types of Thermodynamic Systems
What is an isolated system?
An isolated system has no exchange of energy or matter between the system and its surroundings.
p.3
State Functions and Internal Energy
What are state functions or state variables?
Properties such as pressure (p), volume (V), temperature (T) that depend only on the state of the system.
p.3
State Functions and Internal Energy
What is internal energy (U) in thermodynamics?
The total energy of the system, which may include chemical, electrical, mechanical, or other forms of energy.
p.8
Enthalpy and Its Applications
What does ∆H represent in thermodynamics?
The heat absorbed by the system at constant pressure.
p.2
Types of Thermodynamic Systems
What is a closed system?
A system where there is no exchange of matter, but energy can be exchanged with the surroundings.
p.8
Work, Heat, and the First Law of Thermodynamics
What is the equation for pressure-volume work involving gases?
p∆V = ∆ngRT, where ∆ng is the change in the number of moles of gas.
p.4
Work, Heat, and the First Law of Thermodynamics
What is Joule's significant conclusion regarding work and temperature change?
Joule concluded that a given amount of work done on a system produces the same change of state, as measured by temperature change, regardless of the method used.
p.10
Heat Capacity and Measurement Techniques
What is denoted by C_V?
The heat capacity at constant volume.
p.11
Enthalpy and Its Applications
What does the negative sign in the calculated heat change indicate?
The negative sign indicates the exothermic nature of the reaction.
p.11
Enthalpy and Its Applications
Why can ∆H be equal to ∆U for the given combustion reaction?
Because ∆ng = 0, meaning there is no change in the number of moles of gas during the reaction.
p.3
Types of Thermodynamic Systems
Give an example of an isolated system.
The presence of reactants in a thermos flask or any closed insulated vessel.
p.6
Work, Heat, and the First Law of Thermodynamics
What happens to the sign of work when compression occurs?
The work done is positive since (V_f - V_i) is negative, and negative multiplied by negative gives positive.
p.2
Types of Thermodynamic Systems
What is an open system?
A system where there is an exchange of energy and matter with the surroundings.
p.1
Hess's Law and Thermochemical Equations
What is Hess's law of constant heat summation?
A principle used to calculate enthalpy changes.
p.5
State Functions and Internal Energy
How can we measure internal energy?
We can only measure the changes in internal energy, ∆U of the system.
p.8
Enthalpy and Its Applications
What is the significance of defining enthalpy H?
Enthalpy H is useful for reactions at constant atmospheric pressure.
p.5
Work, Heat, and the First Law of Thermodynamics
What type of work does this document primarily focus on?
Mechanical work, specifically pressure-volume work.
p.4
State Functions and Internal Energy
What are some examples of familiar state functions?
Some familiar state functions include volume (V), pressure (p), and temperature (T).
p.13
Enthalpy and Its Applications
What is the standard enthalpy of vaporization for water (H2O) at its boiling point?
Δ vap H° = +40.79 kJ mol⁻¹.
p.2
Types of Thermodynamic Systems
What is a boundary in thermodynamic terms?
The separation between the system and the surroundings.
p.6
Work, Heat, and the First Law of Thermodynamics
What is represented by the shaded area in a pV-plot during compression?
The shaded area represents the work done on the gas.
p.8
State Functions and Internal Energy
Why is the difference between ∆H and ∆U usually not significant?
Because solids and liquids do not undergo significant volume changes upon heating.
p.9
Heat Capacity and Measurement Techniques
What does the coefficient C represent in the heat transfer equation?
C is called the heat capacity.
p.4
State Functions and Internal Energy
How is internal energy defined in relation to work done on a system?
The internal energy U is defined such that the adiabatic work required to change the state of the system is equal to the difference in internal energy between two states (∆U = U_2 - U_1 = w_ad).
p.10
Heat Capacity and Measurement Techniques
What does C_p represent?
The heat capacity at constant pressure.
p.14
Enthalpy and Its Applications
What are the reference states for carbon and sulfur?
C graphite for carbon and S rhombic for sulfur.
p.2
Types of Thermodynamic Systems
What constitutes the surroundings in thermodynamics?
Everything other than the system.
p.3
Types of Thermodynamic Systems
What characterizes an adiabatic system?
There is no transfer of heat between the system and its surroundings.
p.1
State Functions and Internal Energy
What are state functions in thermodynamics?
Properties like internal energy (U) and enthalpy (H).
p.2
Types of Thermodynamic Systems
How can a system be defined aside from physical boundaries?
By a set of Cartesian coordinates specifying a particular volume in space.
p.10
Heat Capacity and Measurement Techniques
What is the specific heat of a substance?
The amount of heat required to raise the temperature of one unit mass of a substance by one degree Celsius (or one Kelvin).
p.7
Work, Heat, and the First Law of Thermodynamics
What is free expansion?
The expansion of a gas in a vacuum where no work is done.
p.14
Enthalpy and Its Applications
What are the reference states for dihydrogen and dioxygen?
H2 gas for dihydrogen and O2 gas for dioxygen.
p.4
Work, Heat, and the First Law of Thermodynamics
How can internal energy be changed by heat transfer?
Internal energy can be changed by transferring heat (q) from the surroundings to the system or vice-versa without doing work.
p.11
Enthalpy and Its Applications
What is the enthalpy change for the combustion of 1g of graphite according to the calorimetry problem?
The enthalpy change is -20.7 kJ for the combustion of 1g of graphite.
p.13
Enthalpy and Its Applications
What does the magnitude of the enthalpy change during phase transformations depend on?
The strength of the intermolecular interactions in the substance undergoing the phase transformations.
p.6
Work, Heat, and the First Law of Thermodynamics
What is the formula for work done on the system during compression?
w = -p_ex ΔV = -p_ex (V_f - V_i), where ΔV = V_f - V_i.
p.1
Energy Transformations in Chemical Reactions
What is a key question thermodynamics helps to answer regarding chemical reactions?
How to determine the energy changes involved in a chemical reaction.
p.8
Energy Transformations in Chemical Reactions
What is true about ∆H in exothermic reactions?
∆H is negative for exothermic reactions which evolve heat.
p.9
Energy Transformations in Chemical Reactions
What is the thermodynamic equation relating the change in enthalpy to internal energy during vaporization of water?
∆H = ∆U + ∆ng RT, or ∆U = ∆H - ∆ng RT.
p.8
Enthalpy and Its Applications
How can you calculate ∆H from ∆U?
Using the equation ∆H = ∆U + ∆ngRT.
p.5
Work, Heat, and the First Law of Thermodynamics
What is the change in internal energy if work is done by the system and heat is supplied to the system?
∆U = q - w, indicating a closed system.
p.11
Enthalpy and Its Applications
What characterizes an endothermic reaction in terms of heat change?
In an endothermic reaction, heat is absorbed, so qp is positive and ∆rH is also positive.
p.9
Extensive and Intensive Properties
Can you give examples of extensive and intensive properties?
Extensive properties include mass, volume, and heat capacity; intensive properties include temperature, density, and pressure.
p.2
Types of Thermodynamic Systems
What does a system refer to in thermodynamics?
The part of the universe in which observations are made.
p.1
Types of Thermodynamic Systems
What are macroscopic properties that remain constant in an equilibrium state?
Pressure and temperature.
p.1
Types of Thermodynamic Systems
What are the three types of systems described in thermodynamics?
Closed, open, and isolated systems.
p.5
Work, Heat, and the First Law of Thermodynamics
What does the equation ∆U = q + w depend on?
It depends only on the initial and final states of the system, not on how the change is carried out.
p.1
State Functions and Internal Energy
What does entropy represent in thermodynamics?
A state function that is associated with the spontaneity of processes.
p.5
Work, Heat, and the First Law of Thermodynamics
What is the change in internal energy if no work is done and heat is taken out from the system?
∆U = -q, with thermally conducting walls.
p.11
Enthalpy and Its Applications
What characterizes an exothermic reaction in terms of heat change?
In an exothermic reaction, heat is evolved, so qp is negative and ∆rH is also negative.
p.5
Work, Heat, and the First Law of Thermodynamics
What is the significance of the external pressure (p_ex) in a cylinder with an ideal gas?
If p_ex is greater than the internal pressure (p), the piston moves inward, doing work on the gas.
p.12
Enthalpy and Its Applications
What are standard conditions for enthalpy changes?
Substances are in their pure form at 1 bar and a specified temperature, usually 298 K.
p.6
Work, Heat, and the First Law of Thermodynamics
What does the negative sign in the work formula indicate?
It indicates that work is done on the system during compression.
p.6
Work, Heat, and the First Law of Thermodynamics
What is the condition for pressure during an infinitesimal compression?
The external pressure p_ex is always infinitesimally greater than the pressure of the gas.
p.2
Types of Thermodynamic Systems
Provide an example of an open system.
Reactants in an open beaker.
p.5
Laws of Thermodynamics
What is the first law of thermodynamics commonly stated as?
The law of conservation of energy; energy can neither be created nor destroyed.
p.14
Enthalpy and Its Applications
What does the subscript ‘f’ in ∆fH° indicate?
That one mole of the compound has been formed in its standard state from its elements.
p.9
Extensive and Intensive Properties
What distinguishes extensive properties from intensive properties in thermodynamics?
Extensive properties depend on the quantity of matter, while intensive properties do not.
p.10
Heat Capacity and Measurement Techniques
What is the relationship between C_p and C_V for an ideal gas?
C_p - C_V = R, where R is the ideal gas constant.
p.8
Enthalpy and Its Applications
What happens when heat is absorbed by the system at constant pressure?
Changes in enthalpy (∆H) are measured.
p.1
Energy Transformations in Chemical Reactions
What does thermodynamics study?
The transformations of energy in macroscopic systems.
p.6
Work, Heat, and the First Law of Thermodynamics
How is work done calculated when pressure changes in finite steps?
It is calculated as w = -Σ p ΔV.
p.3
Types of Thermodynamic Systems
What is an adiabatic process?
A process in which heat transfer does not occur between the system and surroundings.
p.5
Work, Heat, and the First Law of Thermodynamics
What happens to internal energy (∆U) in an isolated system?
If w = 0 and q = 0, then ∆U = 0.
p.1
Enthalpy and Its Applications
What does Gibbs energy change (∆G) indicate?
It indicates the spontaneity of a reaction and relates to the equilibrium constant.
p.7
Work, Heat, and the First Law of Thermodynamics
How can work be related to internal pressure of the system under reversible conditions?
By using the equation w_rev = ∫(p_ext dV).
p.12
Enthalpy and Its Applications
What is the formula for calculating the enthalpy change in a chemical reaction?
ΔH = [Hm (CO2, g) + 2 Hm (H2O, l)] – [Hm (CH4, g) + 2 Hm (O2, g)]
p.11
Enthalpy and Its Applications
How is the enthalpy change for a reaction calculated using a calorimeter?
q = -CV × ∆T, where q is the heat from the reaction mixture and CV is the heat capacity of the calorimeter.
p.9
Extensive and Intensive Properties
What is a molar property?
The value of an extensive property per mole of substance.
p.13
Enthalpy and Its Applications
What is sublimation?
The direct conversion of a solid into its vapor.
p.12
Enthalpy and Its Applications
What happens to heat during the freezing of water?
Equal amount of heat is given off to the surroundings as the process is reversed.
p.1
Laws of Thermodynamics
What do the laws of thermodynamics primarily focus on?
Energy changes of macroscopic systems.
p.2
Types of Thermodynamic Systems
What is the relationship between the universe, the system, and the surroundings?
The universe = The system + The surroundings.
p.6
Work, Heat, and the First Law of Thermodynamics
What is the relationship of external pressure in an expansion process?
In an expansion process, the external pressure p_ex is less than the internal pressure p_in.
p.2
Types of Thermodynamic Systems
Provide an example of a closed system.
Reactants in a closed vessel made of conducting material (e.g., copper or steel).
p.5
Work, Heat, and the First Law of Thermodynamics
What is the change in internal energy if no heat is absorbed and work is done on the system?
∆U = w, and the wall is adiabatic.
p.9
Heat Capacity and Measurement Techniques
What is the relationship between heat capacity and temperature rise?
The increase in temperature is proportional to the heat transferred.
p.4
Work, Heat, and the First Law of Thermodynamics
What happens to internal energy when work is done on the system?
The internal energy of the system increases and is considered positive when work is done on it.
p.9
Extensive and Intensive Properties
In a gas, what happens to the temperature when the volume is halved?
The temperature remains the same, demonstrating that temperature is an intensive property.
p.10
Heat Capacity and Measurement Techniques
Under what conditions are energy changes measured in calorimetry?
At constant volume (q_V) and at constant pressure (q_p).
p.13
Enthalpy and Its Applications
What is the standard enthalpy of sublimation for dry ice (CO2)?
Δ sub H° = 25.2 kJ mol⁻¹.
p.16
Laws of Thermodynamics
What happens to the value of ΔrH° when a reaction equation is reversed?
The value of ΔrH° is reversed in sign.
p.9
Heat Capacity and Measurement Techniques
What is molar heat capacity?
The heat capacity for one mole of a substance, representing the quantity of heat needed to raise the temperature of one mole by one degree Celsius (or Kelvin).
p.12
Enthalpy and Its Applications
What does the standard enthalpy of reaction represent?
The enthalpy change for a reaction when all substances are in their standard states.
p.8
State Functions and Internal Energy
Why is enthalpy a state function?
Because it depends on state functions U, p, and V, which are independent of path.
p.14
Enthalpy and Its Applications
What does p∆v signify during the change from liquid to solid state?
Negligible change in volume, therefore p∆v = 0.
p.10
Heat Capacity and Measurement Techniques
What is the effect of temperature change in a bomb calorimeter?
It is converted to q_V using the known heat capacity of the calorimeter.
p.7
Work, Heat, and the First Law of Thermodynamics
In Problem 5.4, for 1 mol of an ideal gas expanding reversibly, how is the work calculated?
Using the formula w = 2.303 nRT log(V_f/V_i).
p.15
Enthalpy and Its Applications
How is the standard enthalpy change for a reaction calculated?
ΔrH° = Σ a_i ΔfH°(products) - Σ b_i ΔfH°(reactants).
p.12
Enthalpy and Its Applications
What is the standard state of a substance?
The pure form of the substance at a specified temperature and 1 bar.
p.4
Work, Heat, and the First Law of Thermodynamics
What sign convention does IUPAC recommend for heat transfer?
IUPAC recommends that q is positive when heat is transferred into the system and negative when heat is transferred out of the system.
p.14
Enthalpy and Its Applications
What can be concluded about ∆H and ∆U in the context provided?
∆H = ∆U = -13.56 kJ mol⁻¹.
p.4
Work, Heat, and the First Law of Thermodynamics
What occurs when heat is transferred to the system?
The internal energy of the system increases, and q is considered positive in this case.
p.12
Enthalpy and Its Applications
How is the melting of ice characterized in terms of enthalpy?
Melting is endothermic, requiring heat, with all enthalpies of fusion being positive.
p.10
Heat Capacity and Measurement Techniques
Why is the bomb calorimeter sealed?
To ensure that no heat is lost to the surroundings.
p.16
Hess's Law and Thermochemical Equations
What is Hess’s Law?
The total enthalpy change for a reaction is the sum of the enthalpy changes of the individual steps.
p.13
Enthalpy and Its Applications
What is the definition of standard enthalpy of vaporization?
The amount of heat required to vaporize one mole of a liquid at constant temperature and under standard pressure (1 bar).
p.4
Work, Heat, and the First Law of Thermodynamics
What is the relationship between temperature difference and heat absorbed by the system?
The heat absorbed by the system can be measured in terms of the temperature difference (T_B - T_A) when heat is transferred through thermally conducting walls.
p.16
Enthalpy and Its Applications
What does it mean that enthalpy is an extensive quantity?
The enthalpy change varies with the amount of substance involved in the reaction.
p.15
Enthalpy and Its Applications
What is the standard molar enthalpy of formation (ΔfH°)?
It is the enthalpy change when one mole of a compound is formed from its constituent elements.
p.15
Energy Transformations in Chemical Reactions
What is the significance of the negative sign in ΔrH°?
It indicates that the reaction releases heat (exothermic).
p.12
Enthalpy and Its Applications
What does ΔfusH° represent?
The enthalpy change that accompanies the melting of one mole of a solid substance in standard state.
p.7
Work, Heat, and the First Law of Thermodynamics
In the isothermal irreversible change, how is heat (q) expressed?
q = -w = p_ext (V_f - V_i).
p.13
Enthalpy and Its Applications
What is the change in enthalpy for the process of heating water from 0°C to 100°C?
Δ H1 = -7560 J mol⁻¹ = -7.56 kJ mol⁻¹.
p.7
Work, Heat, and the First Law of Thermodynamics
What is the expression for the work done during isothermal reversible expansion?
w_rev = -nRT ln(V_f/V_i).
p.10
Heat Capacity and Measurement Techniques
How is heat absorbed at constant volume measured?
Using a bomb calorimeter.
p.12
Enthalpy and Its Applications
What is the significance of knowing enthalpy changes in industrial chemical reactions?
It is required to plan the heating or cooling to maintain constant temperature.
p.16
Enthalpy and Its Applications
What is the purpose of calculating heat of reaction?
To determine the enthalpy change for a chemical reaction.
p.13
Enthalpy and Its Applications
Why does it require less heat to vaporize 1 mole of acetone compared to 1 mole of water?
Because the intermolecular dipole-dipole interactions in acetone are significantly weaker than the strong hydrogen bonds in water.
p.13
Enthalpy and Its Applications
What is the total enthalpy change when 1 mol of water is converted to ice?
Δ H = Δ H1 + Δ H2 = -7.56 kJ + (-6.00 kJ) = -13.56 kJ.
p.15
Thermochemical Equations
In a thermochemical equation, what do the coefficients represent?
They refer to the number of moles of reactants and products involved in the reaction.
p.11
Enthalpy and Its Applications
What is the formula for the enthalpy change of a chemical reaction?
∆rH = (sum of enthalpies of products) - (sum of enthalpies of reactants).
p.13
Enthalpy and Its Applications
What is the formula for calculating internal energy change during vaporization?
Δ vap U = Δ vap H° - pΔV = Δ vap H° - ΔngRT.
p.15
Energy Transformations in Chemical Reactions
What is the enthalpy change for the decomposition of calcium carbonate (CaCO3)?
ΔrH° = 178.3 kJ mol–1, indicating it is an endothermic process.
p.16
Enthalpy and Its Applications
What is the formula used to calculate the overall reaction enthalpy (?ΔfH?) in the given example?
ΔfH1° = 3(–285.83 kJ mol–1) - 1(–824.2 kJ mol–1).
p.16
Hess's Law and Thermochemical Equations
How do you obtain one mole of CO(g) from the reaction CO2(g) → CO(g) + O2(g)?
By reversing the original equation and changing the sign of ΔrH°.
p.16
Hess's Law and Thermochemical Equations
What is the enthalpy change for the reaction C (graphite, s) + O2 (g) → CO (g)?
It is not directly measurable but can be calculated using related reactions.
p.15
Energy Transformations in Chemical Reactions
What does it mean if a reaction has a negative ΔrH°?
It indicates that the reaction is exothermic.
p.15
Thermochemical Equations
What is a thermochemical equation?
A balanced chemical equation that includes the value of ΔrH°.
