Worksheet: The Clausius–Clapeyron Equation

In this worksheet, we will practice using the Clausius–Clapeyron equation to convert between changes in temperature and vapor pressure.

Q1:

Under 101.3 kPa of atmospheric pressure, the boiling point of acetone is 56.5C and the enthalpy of vaporization is 31.3 kJ/mol. Estimate the vapor pressure of acetone at 25.0C.

Q2:

The vapor pressure of isooctane is 10.0 kPa at 34.0C and 100.0 kPa at 98.8C. Estimate the enthalpy of vaporization of isooctane.

Q3:

The vapor pressure of ethanol is 5.95 kPa at 20.0C and 75.0 kPa at 63.5C. Estimate the enthalpy of vaporization of ethanol.

Q4:

When the temperature of a liquid is increased, the vapor pressure increases from 𝑃 to 𝑃. How does the ratio 𝑃𝑃 vary with the enthalpy of vaporization?

  • AExponentially
  • BLinearly
  • CLogarithmically
  • DQuadratically
  • EInversely

Q5:

For a compound X, what enthalpy change is associated with the shown process?

  • AEnthalpy of fusion
  • BEnthalpy of vaporization
  • CLattice enthalpy
  • DEnthalpy of sublimation
  • EEnthalpy of formation

Q6:

The normal boiling point of Br2 is 331.9 K, and its vapor pressure at 298 K is 0.287 bar. Within the approximations inherent to the Clausius-Clapeyron equation, what value of Δ𝐻vap (the molar enthalpy of vaporization) for Br2 would be compatible with this data?

  • A 3 0 . 7 kJ/mol
  • B 1 2 . 6 kJ/mol
  • C 33.2 kJ/mol
  • D 70.6 kJ/mol

Q7:

At 22C, the vapor pressure of chloroform is 22.4 kPa and the enthalpy of vaporization is 31.40 kJ/mol. Estimate the boiling point of chloroform under 1 bar of atmospheric pressure.

Q8:

Under 1.00 bar of atmospheric pressure, the boiling point of furan is 31.4C and the enthalpy of vaporization is 27.71 kJ/mol. Estimate to 3 significant figures the vapor pressure of furan at 10.0C.

Q9:

Under 1.000 bar of atmospheric pressure, the boiling point of nitromethane is 101.0C. The vapor pressure at 50.5C is 15.48 kPa. Estimate to 3 significant figures the enthalpy of vaporization of nitromethane.

Q10:

Which of the following statements is incorrect?

  • AThe Clausius–Clapeyron equation can be used in the characterization of solid–liquid phase equilibria.
  • BIt is impossible for four phases of a single pure substance to coexist at equilibrium.
  • CTwo phases at equilibrium must have the same pressure.
  • DThe maximum number of phases that can coexist in a system composed of four components is equal to six.

Q11:

Which of the following provides a succinct statement of the Clausius inequality?

  • A d d 𝑆 𝑞 𝑇 for all isothermal processes carried out reversibly or irreversibly at a constant temperature 𝑇.
  • B d 𝑆 0 for all spontaneous processes occurring in any kind of system.
  • C d 𝐺 0 for a spontaneous process occurring in an isolated system.
  • D d d 𝑆 𝑞 𝑇 r e v for any reversible process carried out at a constant temperature 𝑇.

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