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 5 6 . 5 C and the enthalpy of vaporization is 31.3 kJ/mol. Estimate the vapor pressure of acetone at 2 5 . 0 C .

Q2:

The vapor pressure of isooctane is 10.0 kPa at 3 4 . 0 C and 100.0 kPa at 9 8 . 8 C . Estimate the enthalpy of vaporization of isooctane.

Q3:

The vapor pressure of ethanol is 5.95 kPa at 2 0 . 0 C and 75.0 kPa at 6 3 . 5 C . Estimate the enthalpy of vaporization of ethanol.

Q4:

When the temperature of a liquid is increased, the vapor pressure increases from 𝑃 1 to 𝑃 2 . How does the ratio 𝑃 𝑃 2 1 vary with the enthalpy of vaporization?

  • ALinearly
  • BLogarithmically
  • CInversely
  • DExponentially
  • EQuadratically

Q5:

For a compound X, which enthalpy change is associated with the process X ( ) X ( ) s g ?

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

Q6:

The normal boiling point of B r 2 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 Δ 𝐻 v a p , 𝑚 (the molar enthalpy of vaporization) for B r 2 would be compatible with this data?

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

Q7:

At 2 2 C , 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 3 1 . 4 C and the enthalpy of vaporization is 27.71 kJ/mol. Estimate to 3 significant figures the vapor pressure of furan at 1 0 . 0 C .

  • A 55.6 kPa
  • B 78.6 kPa
  • C 22.9 kPa
  • D 43.7 kPa
  • E 32.1 kPa

Q9:

Under 1.000 bar of atmospheric pressure, the boiling point of nitromethane is 1 0 1 . 0 C . The vapor pressure at 5 0 . 5 C is 15.48 kPa. Estimate to 3 significant figures the enthalpy of vaporization of nitromethane.

Q10:

Which of the following statements is incorrect?

  • AThe maximum number of phases that can coexist in a system composed of four components is equal to six.
  • 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 Clausius-Clapeyron equation can be used in the characterization of solid-liquid phase equilibria.

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