Why do heats of reaction change if different phases are given for products and reactants?

What conditions are used for the standard heat of reaction?

At the conditions of interest, the heat of reaction for the equation A + 2B -> C is -140 kJ. What is the enthalpy change in kJ if 2 moles of A are consumed in the reaction?

At the conditions of interest, the heat of reaction for the equation 2A + 3B -> is -100 kJ. What is the enthalpy change in kJ if 9 moles of B are consumed in the reaction?

What is the main problem with using a calorimeter to determine heat of reaction?

Given the following reactions, what is the enthalpy change for the reaction 3D -> A + 3B + 5C in kJ?

(1) A -> 3B + C, Hr = 100 kJ

(2) A + C -> D + B, Hr = -200 kJ

Given the following reactions, what is the enthalpy change for the reaction 4A + 2C -> 3D + 6B in kJ?

(1) A -> 3B + C, Hr = 100 kJ

(2) A+ C -> D + B, Hr = -200 kJ

Given the following data, what is the heat of reaction for A (g) + B(g) + O₂ (g) -> C (g) in kJ?

What expression would give the heat of reaction for the reaction CH₄ (g) + Cl₂ (g) -> CH₃Cl (g) + HCl (g)?

The standard heat of formation for the oxygen atom is zero.

Which of the following are assumptions made when determining and using heats of combustion? Select all that apply.

For which of the following reactions would the heat of reaction be equal to the heat of combustion? Select all that apply.

Select all methods discussed for choosing enthalpy reference states and calculating specific enthalpies

In the heat of formation method, what reference states are most convenient to choose when there are reacting species?

In the heat of formation method, what is specific enthalpy determined from?

When should the heat of formation method be used? Select all that apply.

In the heat of reaction method, what reference states should you choose?

What does solving an adiabatic energy balance typically involve?

In an endothermic reaction, a greater extent of reaction would correspond to a higher outlet temperature?

The absolute value of the internal energy at specified state (temperature, pressure, and phase) can be determined by comparing its energy to a reference state.

A reference state is an arbitrary state set to have an internal energy of zero in order to aid in the determination of specific internal energies and enthalpies for different states

We are allowed to use hypothetical process paths in our calculations for using the specific internal energy and enthalpy because these are both state properties and do not depend on the path chose.

When constructing a hypothetical pathway for a system undergoing a phase change, in order to evaluate the change in specific enthalpy, Ĥ, one should first calculate the ΔĤ between the current state and the substance’s normal phase transition temperature and pressure, followed by the ΔĤ of the phase transition. Finally, one should calculate the between the state after its phase transition and its final state.

What is the reference state used in Table B.5 to determine specific internal energies and enthalpies

Which of the following can be used as part of a hypothetic process path to calculate the specific internal energy or enthalpy change? Select all that apply.

Which of the following are hypothetical pathways that could be used to calculate the change in specific enthalpy for a system containing liquid ethanol (Etoh) at an initial state of (l, 20°C, 1 atm) to a final state of (g, 100°C, 1 atm)?

Which of the following hypothetical pathways for the transition of ethanol (Etoh) from an initial state of (l, 20°C, 1 atm) to a final state of (g, 100°C, 1 atm) would be the easiest to calculate given the tables in Appendix B?

Which assumptions can be applied for the isothermal processes of O2 (l, 1 atm) → O2 (l, 1000 atm)?

Which assumptions can be applied for the isothermal processes of O2 (g, 1 atm) → O2 (l, 0.98 atm)?

Which assumptions can be applied for the isothermal processes of benzene (l, 1 atm) → benzene (l, 1000 atm)?

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The relationship between Cv and Cp does not depend on phase.

If the heat capacity at constant pressure for an ideal gas is 38.01 J/mol K, what is the heat capacity at constant volume for this species?

Estimate the heat capacity at constant pressure for liquid ethanol using Table B.10.

A solute has a heat capacity of 2 cal/g °C and is in a mixture with a solvent having a heat capacity of 3.5 cal/g °C. Knowing that the mixture contains 0.1% by mass solute, it can be said that the heat capacity of the mixture is 2.75 cal/g °C.

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A spreadsheet program may provide an easier method of solving polynomial functions such as heat capacity formulas.

The trapezoidal rule method of numerical integration is more accurate than Simpson’s rule.

Equations should be solved analytically when a solution cannot be found using numerical integration.

The heat of freezing can be found by taking the negative of the heat of fusion found in the literature.

The latent heat is the enthalpy change associated with temperature changes for a single phase system.

The latent heat of a phase change is a constant value that represents the enthalpy change of the transition at any temperature and pressure.

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Watson’s correlation allows you to estimate the heat of vaporization at a different temperature given an initial heat of vaporization at an initial temperature.

Calculating specific enthalpy changes in multiphase systems can be approached in a similar manner to single-phase systems with the addition of accounting for the phase transitions of all components.

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Heat is defined as positive when it is transferred from the surroundings to the system.

What is meant by the term potential energy?

The law of conservation of energy states:

The rate of change in the kinetic energy of a fluid flowing in a system can be found by substituting the mass flow rate into the equation for kinetic energy.

Kinetic energy equals

What is the potential energy of water that has been pumped at a rate of 10 kg/s for 10 seconds from the ground to a point 10 m above the ground?

The basic form of the first law of thermodynamics is:

If a system is not accelerating, rising, or falling, then the first law reduces to:

A system to which no heat is added or withdrawn is said to be:

Shaft work is the rate of work done by the process fluid on a moving part within the system.

Flow work is defined to be:

H = U - PV

If the volume of a fluid is 10 m³ and the mass of the fluid is 5 g, what is the specific volume of the fluid?

A property that is defined on a specific mass or molar basis is what type of quantity?

The first law of thermodynamics for an open system at steady-state has the form “input = output.”

Simplify Eq. 7.4-15 for a system with all streams at the same height and no moving parts.

At the reference state, Ĥ = 0.

The changes in the enthalpy and internal energy of a substance depend on the path the substance follows from the initial state to the final state.

The specific enthalpy of vapor A relative to liquid A at 0°C and 1 atm is 2000 J/kg. What is the Ĥ of the liquid A at 0°C and 1 atm? The reference state for this liquid is 0°C and 1 atm.

Which of the following are state properties? Select all that apply.

In the superheated steam table, there are temperatures and pressures where the water is a liquid.

In the superheated steam tables, if you are given a temperature and a pressure of water, you can locate the specific properties at the intersection of the column corresponding to the given temperature and the row corresponding to the given pressure.

The reference state for Û or Ĥ in the saturated steam tables is relative to liquid water at the triple point.

At points on the vapor–liquid equilibrium curve on a phase diagram, water may be:

The difference between the specific enthalpy of saturated liquid and saturated steam is the:

The change in internal energy equals the heat (Q) in open systems.

What type of substance has a temperature above its critical temperature and a pressure above its critical pressure?

Mechanical and energy balances can be solved simultaneously.

When process streams contain several components, the specific enthalpies of each component must be determined separately and substituted in the energy balance equation when the total change in enthalpy in all components is evaluated.

It is important to distinguish the state of a species (i.e., solid, liquid, vapor) during energy balance calculations.

It is not common to neglect the kinetic and potential energy changes relative to enthalpy changes for processes that involve phase changes, chemical reactions, or large temperature changes.

Refer to Figure 6.1-1. If the pressure is 3 mm Hg, at what temperature(s) would you expect water to be a solid? Select all that apply.

Refer to Figure 6.1-1. If the temperature is 2°C, at what pressure(s) would you expect water to be a vapor?

Above and to the right of the critical point is a phase called the supercritical fluid, which is where separate phases do not coexist.

“Volatility” means tendency to explode.

Which of the following is a measure of volatility?

What does latent heat of vaporization measure?

Equal temperature reference-substance plots are intended to do what?

Which of the following would be considered intensive variables? Select all that apply.

Under which conditions should the Gibbs phase rule not be applied?

How many degrees of freedom are there if water and ethanol exist in equilibrium in both the liquid and vapor phases?

What term is applied to a gas phase saturated with a liquid that it coexists with?

If the partial pressure of component A exceeds the vapor pressure of component A, which of the following will occur?

What is a possible cause of dry skin during the winter?

Which of the following systems most closely corresponds to having 100% humidity?

You cannot change the pressure of an incompressible liquid.

What does it mean for a substance to be “incompressible”?

The volume additivity assumption is most likely valid when dealing with which of the following?

The ideal-gas equation of state provides accurate results under all conditions of temperature and pressure.

At what pressure will a gas deviate from ideal behavior?

An equation of state relates the molar quantity and volume of a gas to:

For the SI system, standard temperature and pressure are:

What happens to the volume of an ideal gas if you halve the temperature at a fixed pressure?

A volumetric flowrate of 20 SCMH represents:

For an ideal-gas mixture, the mole fraction equals the volume fraction.

The partial pressures of the component species of an ideal-gas mixture add up to the total pressure of the mixture.

For a mixture that is 70% N2 and 30% H2O by volume at a total pressure of 10 atm, what is the partial pressure of N2?

The critical pressure is the pressure required to liquefy a gas at its critical temperature.

The terms gas and vapor can be used interchangeably; there is no technical difference between these terms.

Using Table B.1, what is the critical temperature of toluene in Kelvin (K)?

What is the term used to describe the temperature point above which a gas cannot be liquefied, whatever pressure is applied?

If process conditions are such that the ideal-gas equation of state is a poor approximation, a more complex species-specific equation of state must be used.

The ideal-gas equation of state cannot be obtained from the virial equation of state.

The Pitzer acentric factor is a parameter that reflects the geometry and polarity of a molecule.

The second virial coefficient, B, in the virial equation of state is a function of:

All equations of state are approximations.

The compressibility factor, z, is a measurement used to determine the extent to which the gas is behaving nonideally.

An ideal gas has a compressibility factor of 1.

If the compressibility factor is greater than 1, the gaseous species behaves as:

The compressibility factor, z, depends on the temperature, pressure, and chemical species.

According to the generalized compressibility charts, as pressure approaches the critical pressure there are decreasing deviations from ideal-gas behavior.

Absolute temperature and pressure must be used when working with the law of corresponding states.

A compressibility chart for each species would be required to find the compressibility factor if the critical temperature and pressure were not converted to a generalized reduced temperature and pressure.

For which gas(es) must Newton’s corrections be used? Select all that apply.

Kay’s Rule estimates pseudocritical properties of mixtures as simple averages of pure-component critical constants.

Pseudocritical constants can be calculated by weighting the critical constants for each mixture component by the mole fraction of that component in the mixture.

Kay’s Rule can be used to accurately describe mixtures of nonpolar compounds whose critical temperature and critical pressure are within a factor of 100 of one another.

Which values can be calculated using Kay’s Rule? Select all that apply.

A continuous process is considered to be transient during the start-up phase and immediately following process changes.

A continuous process is considered to be at steady-state during the initial start-up of a system and at unsteady-state after a long period of time has elapsed.

Continuous processes are most commonly used to produce a relatively small amount of a particular product on a single occasion.

Which of the following would be classified as a continuous process?

Which of the following would be classified as a semi-batch process?

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What kind of balance (differential or integral) should be used to determine how many gallons of water are purified per minute in a purification process that operates continuously at steady-state?

Two gases are charged into a closed reaction chamber and allowed to react. What kind of balance (differential or integral) should be used to determine the mass of product produced after the system has come to equilibrium?

For a continuous, steady-state reactor, a mass balance on a nonreactive species would yield the material balance equation to be: Input = Output

For a continuous, steady-state reactor, a mass balance on a nonreactive species would yield the material balance equation to be: Input = Output

Which statement(s) is(are) false about a semi-batch process?

For a batch reactor, the material balance equation for a reactive species is the same as one for a continuous, steady-state reactor; therefore, we can conclude that accumulation is equal to zero in a batch reactor just as it is in a continuous, steady-state reactor.

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If the number of degrees of freedom in a system is greater than or equal to one, there is no point in doing any calculations, because a unique solution cannot be found for any of the unknowns in the system.

A degree-of-freedom analysis can be performed before any calculations are performed.

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How should we approach the degree-of-freedom (DOF) analysis for multiple-unit processes?

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When analyzing a multiple-unit process, one is required to solve the overall balance first before solving other subsystems.

If the degrees of freedom for one subsystem are zero, one may assume that the variables in that subsystem are considered “known” when proceeding to solve the next subsystem.

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Which of the following cannot be said about a reactant that is present in 30% excess in the feed?

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Systems that involve chemical reactions can be analyzed using atomic balances, which will reduce the general balance equation for a steady-state reactive process to be Input = Output.

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In order for two molecular species to be considered independent in a reactive process, they must be present in the same ratio to each other when they appear in the process.

When we utilize the technique of molecular species balance to determine unknown variables for a reactive process, then in the degree-of-freedom analysis, each chemical reaction introduces an additional unknown.

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Every independent reaction in a system adds how many degrees of freedom?

When we utilize the technique of atomic species balance to determine unknown variables for a reactive process, then in the degree-of-freedom analysis, each chemical reaction is an additional unknown.

Generally, in this course, we assume that atomic species are not created or destroyed.

Material balances carried out via the molecular species method, the atomic species method, or the extent of reaction method will always yield the same results.

When we utilize the technique of extent of reaction to determine unknown variables for a reactive process, then in the degree-of-freedom analysis, each chemical reaction introduces an additional unknown.

The overall and single-pass conversions are calculated separately for each individual reactant.

The single-pass conversion is based only on the streams entering and leaving the reactor, while the overall conversion is based on the streams entering and leaving the overall process.

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Purge streams are necessary mainly for inert or insoluble substances because they can accumulate and disrupt the steady-state process of a system.

A purge stream can be used_________.

Partial combustion of butane will include CO2 as a product.

Theoretical air is the amount of O2 needed for the complete combustion of all the fuel fed to a reactor.

Which of the following is a product in the incomplete combustion reaction of ethane? Select all that apply.

Propane undergoes an incomplete combustion reaction. We are told that 200 mol/min of propane is fed to a combustion chamber, and the fractional conversion of propane is 0.3. What quantities and values would be needed to calculate the theoretical amount of oxygen? Select all that apply

The calculations for percent excess air and theoretical air do not consider the presence of incomplete combustion reactions.

The value for theoretical air (in moles) will always be greater than the value for theoretical oxygen.

The density of a given substance could either increase or decrease with an increase in temperature, depending on conditions and the nature of the substance.

Which of the following are units of density? Select all that apply.

What is the most common reference density used in specific gravity calculations?

If 5.0 mL of benzene has a density of 0.879 g/cm3, what is its mass in mg?

It is possible to determine the volumetric flow rate from the mass flow rate and the specific gravity of a fluid.

What is the mass flow rate of diethyl ether (in kg/s) given a volumetric flow rate of 0.36 m³/h and a density of 708 kg/m³?

A rotameter can be used to measure the flow rate of both liquids and gases.

Venturi meters measure flow rates by decreasing the cross-sectional area of a pipe and then increasing the area back to the original size and measuring the pressure drop between a point before the meter and when the pipe has the smallest diameter. Orifice meters also measure the pressure drop between two points to measure flow rates. However, between the measured points is an obstruction along the walls of the pipe. Which device, venturi or orifice meter, would you expect to have a lower pressure drop across the meter?

How many tons of CO2 are in 2 ton-moles of carbon dioxide?

The mass of a lb-mole is 1 lbm for every mole of substance.

What is the molar flow rate (in lb-mole/min) of ethylene glycol (C2H6O2) given a volumetric flow rate of 55.0 ft3/min? Ethylene has an SG of 1.113.

A basis of calculation can be taken if needed to convert a set of mole fractions to mass fractions.

Mass and mole fractions are dependent on their units and require conversions to be expressed in alternate units.

The average molecular weight of a mixture can be calculated by summing the individual molecular weights of each species and dividing by the total number of species.

Which of the following have units corresponding to concentrations? Select all that apply.

It is possible to calculate the volume of a species in a solution given the concentration and number of moles of the species.

All of the following are acceptable units of pressure except:

You must know the densities of two fluids in order to convert between pressures expressed as heads of each fluid.

An absolute pressure can have a negative value.

Which of the following is not a correct value of atmospheric pressure?

Which of the following are equivalent to 15 torr of vacuum?

Two points in a manometer at the same height that are connected by the same fluid always have the same pressure.

Suppose an angled differential manometer is made such that the U-shape of the manometer connects to a pipe at a 45-degree angle. Which manometer will more precisely detect a smaller difference in fluid heights?

Which of the following temperature scales have the same intervals? Select all that apply.

An equivalent temperature range of 293 to 310 Kelvin in Fahrenheit has a difference of 17 degrees

At what temperature are both the Fahrenheit and Celsius temperature scales equivalent?

The bold term in the following statement is a dimension.“The acceleration due to gravity on earth is about 9.8 m/s2.”

Any valid conversion factor will reduce to the dimensionless numerical value 1.

m³, m/s, kg.m/s², and cm are all examples of compound units.

The unit of distance “feet” is a base unit of the American engineering system of units.

When you multiply or divide two numbers, the number of significant figures in the result is equivalent to the lowest number of significant figures in either of the two numbers.

In general, the greater the value of sample standard deviation, the greater the accuracy of the associated experimental value.

In general, the more samples that are used to calculate a sample mean, the more accurate the sample mean will be.

The following is a valid equation.C (cm/min) = Co (cm/min) + g (m/s²) t(s)

The acceleration of gravity on earth is about 32.174 ft/s². What would be the gravitational force (in lb_f) of an object having a mass of 20 lb_m, if that object were on the surface of a planet with a gravitational acceleration equal to 3 times that of Earth?

Which unit system is the unit of distance “meters” a base unit of?

The unit of time “s” is what kind of unit?

Which of the reasons below best explains why the weight of an object would be different on the moon than at sea level but the mass would stay the same?

The total mass of 6 identical cubes is reported to be 45.25 g. In order to determine the mass of a single cube, you enter 45.25/6 into your calculator. After completing the calculation, the screen of your calculator reads “7.5416666666667.” What is the mass of a single cube, rounded to the correct number of significant figures?

Which of the following solutions is not physically possible? (Note: more than one response can be selected.)

You can validate quantitative results by:

Suppose you are producing ammonia in a batch process. After 1 hour, the reaction terminates and you withdraw n moles of ammonia. You perform 20 successive trials (keeping everything constant in each trial) and find that the sample mean of n moles of ammonia after 1 hour is 0.175 moles. Which of the following will most likely take place?

Which is consistent through the following equation?W(Btu) = P(Pa)ΔV1(m3) + W0(Btu)

Linear extrapolation would provide a reasonable estimate for y(x), where the value of x lies far outside of any two consecutive plotted points in the following figure:

Exponential and power functions are just two examples of the many types of functions that can be rearranged to fit the form of a linear equation.

In order to get a straight line for the following function of y in terms of x: y = a exp(b/x)ln(y) would be plotted on the vertical axis, and b/x would be plotted on the horizontal axis.

Which of the following equations would appear as a straight line on a semilog plot? (Note: more than one response can be selected.)

Suppose you have an exponential function in the form y = aebx. Plotting y vs. x using a semilog scale and plotting ln(y) vs. x using a rectangular scale will both yield the following formula for slope.Slope = ln (y2/y1)/(x2 − x1)