Phase Diagrams: Flashcards
Revise reading phase diagrams, the triple and critical points, and the diagrams of water and carbon dioxide.
Phase Diagrams: Flashcards
- QuestionWhat does a phase diagram show?Answer
Which phase of a substance is stable at each temperature (x-axis) and pressure (y-axis).
- QuestionWhat do the lines on a phase diagram represent?Answer
Conditions where two phases coexist in equilibrium (melting, boiling or sublimation points).
- QuestionWhat is the triple point?Answer
The single temperature and pressure at which solid, liquid and gas coexist.
- QuestionWhat is the critical point?Answer
The end of the liquid–gas line; beyond it the substance is a supercritical fluid.
- QuestionWhere are the normal melting and boiling points on a phase diagram?Answer
Where the 1 atm line crosses the solid–liquid and liquid–gas lines.
- QuestionWhy does water's solid–liquid line slope to the left?Answer
Ice is less dense than liquid water, so higher pressure favours the liquid and lowers the melting point.
- QuestionGive the triple point of water.Answer
0.01 °C and 0.00604 atm (611.7 Pa).
- QuestionGive the triple point of CO₂.Answer
−56.6 °C and 5.11 atm.
- QuestionWhy does dry ice sublime at 1 atm?Answer
Its triple-point pressure (5.11 atm) is above 1 atm, so liquid CO₂ cannot exist at 1 atm.
- QuestionIn which state is CO₂ at 100 atm and 40 °C?Answer
Supercritical fluid (above 72.8 atm and 31.0 °C).
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