Ch.11 - Liquids, Solids & Intermolecular ForcesSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

The Clausius-Clapeyron Equation establishes a quantitative relationship between vapor pressure and temperature

Examining the Clausius-Clapeyron Equation

Concept #1: Understanding the Clasius-Clapeyron Equation

Vapor Pressure looks at the equilibrium established between vaporization and condensation. By using the Clasius-Clapeyron equation, the enthalpy of vaporization can be determined. 

Example #1: The heat of vaporization (ΔHvap) of water is 40.3 kJ/mol at its normal boiling point at 100oC. What is the vapor pressure (in mmHg) of water at 60oC?

Additional Problems
Mercury is a neurotoxic metal with a reasonable high vapor pressure, at least for a metal. The vapor pressure at 25°C is 0.0017 mmHg. But what about the vapor pressure of mercury in a factory where the temperature is 32°C? Will the vapor pressure of mercury be higher or lower in the factory? The enthalpy of vaporization of mercury is 59.11 kJ/mol. 
Useful conversions: 760 torr = 1atm = 760 mm Hg. 1 inch = 2.54cm Weather trivia: The lowest ever recorded sea-level atmospheric pressure was 25.69 inches of Hg inside of typhoon Tip, on October 12, 1979. If you had been unlucky enough to be inside of it, at sea level, on that date, what would have been the boiling point of water? The enthalpy of vaporization of water is 40.7 kJ/mol. 1. 101.929°C 2. 99.69°C 3. 98.09°C 4. 100.13°C 5. 95.7131°C  
Calculate the vapor pressure (mmHg) of potassium at 150°C. The normal boiling point of potassium is 775°C. The heat of vaporization is 81.3 kJ/mol   a) 7.82 x 10 -4 mmHg b) 0.451 mmHg c) 237 mmHg d) 2.81 x 10 -2 mmHg e) 624 mmHg
How many of the following would be associated with an increase in the rate of vaporization? • An increase in temperature • An increase in the strength of intermolecular forces • An increase in the amount of surface area • An increase in vapor pressure          A. none           B. one           C. two           D. three           E. four
At room temperature, a sample of some compound has a vapor pressure of 454 torr. At what temperature will the solution have a vapor pressure of 900 Torr? ∆Hvap of compound is 25.8 kJ/mol.  A. 319 K B. 258 K C. 298 K D. 416 K
An unknown liquid has a vapor pressure of 88 mmHg at 45 ◦C and 39 mmHg at 25◦C. What is its heat of vaporization? 1. 32 kJ/mol  2. 2000 J/mol 3. 32000 kJ/mol 4. 2000 kJ/mol
The vapor pressure of benzene, C6H6, is 40.1 mmHg at 1.6 °C. What is its vapor pressure at 60.6 °C? The molar heat of vaporization of benzene is 31.0 kJ/mol.  
Which of the following is NOT true about the Clausius-Clapeyron equation?   A) It is a way to measure the heat of vaporization in the laboratory  B) The equation describes an exponential relationship C) B is a constant based on a particular gas D) Its graph represents the natural log of the vapor pressure by the inverse of temperature E) The graphed data is linear 
How much energy is required to vaporize 98.6 g of ethanol (C2H5OH) at its boiling point, if its ΔHvap is 40.5 kJ/mol?   A) 86.7 kJ B) 11.5 kJ C) 18.9 kJ D) 52.8 kJ E) 39.9 kJ
Which compound has the lowest boiling point?
It was determined that the normal boiling point of a compound was 183.5°C. When the boiling point was measured at 300 mmHg, it was a 136.8°C. What is the heat of vaporization (kJ/mol) of this compound? a. 31.0 KJ/molb. 56.7 KJ/molc. 93.9 KJ/mold. 145 KJ/mole. 188 KJ/mol
What is the vapor pressure (in atm) of a liquid at its normal boiling point? ___________________
The vapor pressure of ammonia at several different temperatures is shown below.a. Use the date to determine the heat of vaporization of ammoniab. Determine the normal boiling point of ammonia.
The normal boiling point of bromine is 58.8°C. Given that the vapor pressure of bromine is 75.0 torr at 2.5°C, calculate the molar enthalpy of vaporization of bromine.a) 3.76 kJ/molb) 2.90 kJ/molc) 29.7 kJ/mold) 3.57 kJ/mole) 31.3 kJ/mol
Ethanol has a heat of vaporization of 38.56 kJ/mol and a normal boiling point of 78.4 °C. What is the vapor pressure of ethanol at 14°C?
A certain substance has a heat of vaporization of 47.70 kJ/mol. At what kelvin temperature will the vapor pressure be 3.50 times higher than it was at 293K?
1) The vapor pressure of dichloromethane, CH 2Cl2, at 0°C is 134 mmHg. The normal boiling point of dichloromethane is 40°C. Calculate its molar heat of vaporization. Express your answer to three significant figures and include the appropriate units. 2) The boiling points for a set of compounds in a homologous series can be qualitatively predicted using intermolecular force strengths. Using their condensed structural formulas, rank the homologous series for a set of alkanes by their boiling point. Rank from highest to lowest boiling point. To rank items as equivalent, overlap them. butane (C4H10), 3,3-dimethylpentane (C7H16), hexane (C6H14), and heptane (C7H16).
Ethanol has a heat of vaporization of 38.56 kJ/mol and a normal boiling point of 78.4 C. What is the vapor pressure of ethanol at 15°C?
Four alcohols have the formula C4H9OH: 1-butanol, 2-butanol (or sec-butanol), isobutanol (or 2-methyl-1-propanol), and tert-butanol (or 2-methy;-2-propanol). They are examples of isomers, or compounds that have the same molecular formula but different molecular structures. The below table gives data on the isomers: Using the Clausius-Clapeyron equation, rank the isomers of butanol in order of decreasing vapor pressure at 25 °C. Does the ranking agree with any conventional wisdom based on the ΔvapH Values or the normal boiling points?
A certain substance has a heat of vaporization of 57.40 kJ/mol. At what Kelvin temperature will the vapor pressure be 3.00 times higher than it was at 317 K? 
The vapor pressure of dichloromethane,CH2Cl2, at 0°C is 134mmHg . The normal boiling point of dichloromethane is 40°C. Calculate its molar heat of vaporization. Express your answer numerically in kilojoules per mole.  
The following equation represents the decomposition of a generic diatomic element in its standard state.1/2 X2(g) → X(g) Assume that the standard molar Gibbs energy of formation of X(g) is 4.76 kJ mol-1 at 2000. K and -65.63 kJ mol-1 at 3000. K. Determine the value of K (the thermodynamic equilibrium constant) at each temperature.K at 2000. K = _____K at 3000. K = _____Assuming that delta H°rxn, is independent of temperature, determine the value of delta H°rxn from these data. ΔH°rxn = ______ kJ mol-1
The formation of methanol is important to the processing of new fuels.At 298.0 K, Kp = 2.25x104 for the reactionCO(g) + 2 H2(g) ⇌ CH3OH(l) If ΔH°rxn = -128 kJ/mol CH3OH, calculate Kp at 0°C. (Enter your answer in scientific notation.)
A certain substance has a heat of vaporization of 43.09 kJ/mol. At what Kelvin temperature will the vapor pressure be 3.00 times higher than it was at 341 K?
A boiled egg can be cooked at 100.0°C in exactly 5 minutes. At an altitude of around 2000m where the boiling point of water is 93.0°C, it takes exactly 7.5 minutes to cook the egg to the same amount. What is the activation energy for the reaction involved when an egg is boiled?•66 kJ/mol•0.5 kJ/mol•7.9 kJ/mol•>100 kJ/mol•4.5 kJ/mol
Part AThe vapor pressure of a substance is measured over a range of temperatures. A plot of the natural log of the vapor pressure versus the inverse of the temperatures (in Kelvin) produces a straight line with a slope of -3.39 x 103 K. Find the enthalpy of vaporization of the substance. Express your answer using three significant figures.
A certain liquid has a vapor pressure of 92.0 Torr at 23.0°C and 372.0 Torr at 45.0°C.Calculate the value of ΔH°vap for this liquid. Calculate the normal boiling point of this liquid.
A reaction has an equilibrium constant of 8.9x103 at 298 K. At 751 K, the equilibrium constant is 0.43. Find Δ Hrxn for the reaction.
A certain liquid has a vapor pressure of 92.0 Torr at 23.0°C and 332.0 Torr at 45.0 C, Calculate the value of ΔHvap for this liquid.Calculate the normal boiling point of this liquid.
Enter your answer in the provided box.The vapor pressure of ethanol is 1.00 x 102 mmHg at 34.90 °C. What is its vapor pressure at 56.17 °C? (ΔHvap for ethanol is 39.3 kJ/mol.) 
A certain liquid has a vapor pressure of 92.0 Torr at 23.0°C and 203.0 Torr at 45.0°C. Calculate the value of ΔH°vap for this liquid. Calculate the normal boiling point of this liquid. 
Enter your answer in the provided box. What is the ΔH° vap of a liquid that has a vapor pressure of 607 torr at 86.5 °C and a boiling point of 93.3 °C at 1 atm?
For a substance with a molar enthalpy of vaporization of 83 kJ/mol, how much must the temperature be lowered from 600 K to decrease the vapor pressure from 800 to 620 torr?
The vapor pressure of liquid aluminum is 400 mm Hg at 2.59 x 103 K. Assuming that its molar heat of vaporization is constant at 252 kJ/mol, the vapor pressure of liquid Al __________ is mm Hg at a temperature of 2.62 x 103 K.
From the following vapor pressure data for acetone, an estimate of the molar heat of vaporization of CH3COCH3 is _______ kJ/mol.
A certain substance has a heat of vaporization of 53.47 kJ/mol. At what Kelvin temperature will the vapor pressure be 6.50 times higher than it was at 299 K?
The vapor pressure of liquid silver is 400 mm Hg at 2.33 x 103 K. Assuming that its molar heat of vaporization is constant at 275 kJ/mol, the vapor pressure of liquid Ag is _______ mm Hg at a temperature of 2.30 x 103 K.
The vapor pressure of ethanol is 1.00 x 102 mmHg at 34.90°C. What is its vapor pressure at 64.07°C? (ΔHvap for ethanol is 39.3 kJ/mol.)
A certain substance has a heat of vaporization of 37.11 kJ/mol. At what Kelvin temperature will the vapor pressure be 4.50 times higher than it was at 347 K?
Enter your answer in the provided box. What is the ΔH°vap of a liquid that has a vapor pressure of 615 torr at 79.8 °C and a boiling point of 96.0 °C at 1 atm? 
Enter your answer in the provided box. Assistance Diethyl ether has a  ΔH vap of 29.1 kJ/mol and a vapor pressure of 0.703 atm at 25.0°C. What is its vapor pressure at 79.0°C?
A certain liquid has a vapor pressure of 92.0 Torr at 23.0°C and 290.0 Torr at 45.0°C. Calculate the value of ΔH°vap for this liquid. 
Enter your answer in the provided box.What is the ΔH°vap of a liquid that has a vapor pressure of 622 torr at 79.0°C and a boiling point of 99.8°C at 1 atm?
The vapor pressure of dichloromethane, CH 2C2, at 0°C is 134 g. The normal boiling point of dichloromethane is 40°C. Calculate its molar heat of vaporization. Express your answer to three significant figures and include the appropriate units. 
The vapor pressure of a liquid doubles when the temperature is raised from 71°C to 8.0 x 101°C. At what temperature will the vapor pressure be five times the value at 71°C?
Which solids will melt under applied pressure? Check all that apply.