Worksheet: Phase Changes at Varying Temperatures

In this worksheet, we will practice explaining the effects of pressure and temperature on phase transitions and predicting the features of a phase diagram.

Q1:

Consider the phase transformation process C(graphite)C(diamond). The value of Δ𝐺 for this process at 1 bar pressure and a temperature of 298 K is 2.900 kJ/mol, and the value of Δ𝑆 for the process under these same pressure and temperature conditions is 3.36 J/K⋅mol. If the temperature increased from 298 K to 1,000 K but the pressure remained constant at 1 bar, would the thermodynamic stability of graphite relative to diamond increase, decrease, or stay the same?

  • AStay the same
  • BThere is not enough information provided to answer this question.
  • CDecrease
  • DIncrease

Q2:

In addition to its two solid phases, diamond and graphite, elemental carbon has one liquid phase and one gas phase. The phase diagram for carbon is shown.

Which of the following phase transitions corresponds to the melting of graphite?

  • APhase 2 to phase 3
  • BPhase 3 to phase 4
  • CPhase 2 to phase 3
  • DPhase 1 to phase 2
  • EPhase 1 to phase 3

Which of the following phase transitions is not possible?

  • AMelting of graphite
  • BSublimation of graphite
  • CMelting of diamond
  • DSublimation of diamond
  • EConversion of graphite to diamond

If the temperature decreases from 5,000 K to 3,000 K at a constant pressure of 10 Pa, which phase transition takes place?

  • ACondensation
  • BSolid–solid transition
  • CFreezing
  • DDeposition
  • ECondensation followed by freezing

If the pressure increases from 10 bar to 10 kbar at a constant temperature of 4,000 K, which phase transition takes place?

  • ADeposition followed by a solid–solid transition
  • BSolid–solid transition
  • CCondensation only
  • DFreezing only
  • ECondensation followed by freezing

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