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What is the primary focus of the content provided?
What is the primary focus of the content provided?
Which of the following best describes the relationship mentioned in the content?
Which of the following best describes the relationship mentioned in the content?
What does 'N' appear to represent in the context of the provided content?
What does 'N' appear to represent in the context of the provided content?
In discussing chemical reactions, which aspect is highlighted in the content?
In discussing chemical reactions, which aspect is highlighted in the content?
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Which of the following processes is likely referenced in relation to hydroxide ions?
Which of the following processes is likely referenced in relation to hydroxide ions?
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What chemical property is indirectly referenced through the values and symbols shown?
What chemical property is indirectly referenced through the values and symbols shown?
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What type of chemical species is likely to interact with hydroxide ions according to the content?
What type of chemical species is likely to interact with hydroxide ions according to the content?
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Which conclusion can be drawn from the relationships discussed in the content?
Which conclusion can be drawn from the relationships discussed in the content?
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What is likely to happen when two phases are in equilibrium?
What is likely to happen when two phases are in equilibrium?
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Which of the following best describes a characteristic of equilibrium in a chemical process?
Which of the following best describes a characteristic of equilibrium in a chemical process?
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In a saturated solution, the solute is:
In a saturated solution, the solute is:
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Which factor does not affect phase equilibrium?
Which factor does not affect phase equilibrium?
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During dynamic equilibrium, which of the following statements is true?
During dynamic equilibrium, which of the following statements is true?
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How does increasing temperature typically affect a solid-liquid equilibrium?
How does increasing temperature typically affect a solid-liquid equilibrium?
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Which concept describes the tendency of a system to return to its equilibrium state after a disturbance?
Which concept describes the tendency of a system to return to its equilibrium state after a disturbance?
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What role does the concept of chemical potential play in phase equilibrium?
What role does the concept of chemical potential play in phase equilibrium?
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Study Notes
Phase Equilibrium
-
A phase is a homogeneous entity within a system, which is heterogeneous with other parts of the system in terms of chemical and physical properties and mechanically separable from other parts of the system.
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Number of phases (p): The number of mechanically separable entities in a system
- Ice in water (p = 2) - Ice can be separated mechanically using a force
- Sand + water + iron nail (p = 3)—Iron nail can be separated with a magnet
- Sugar + water (p = 1) - Not mechanically separable
- Alloys (p = 1) - All alloys have a single phase (e.g., brass, bronze, German silver)
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Number of components (c): The minimum number of independent constituents required to specify the overall composition of a phase.
- Examples:
- Na₂CO₃ + BaCl₂ - Na, K, and BaSO₄ are independent constituents, Na₂SO₄ is not.
- Mathematically: C = N – R – E
- Where:
- N = total number of chemical species
- R= number of equilibrium conditions
- E = number of independent chemical reactions
- Where:
- Examples:
-
Degree of freedom (F): The maximum number of independent variables that can be changed without disturbing one or more phases at equilibrium.
- F = C – P + 2 (Gibbs Phase Rule)
- Where:
- C = number of components
- P = number of phases
- Where:
- F = C – P + 2 (Gibbs Phase Rule)
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If ions are involved, electroneutrality conditions are also included (the condition that a solution be electrically neutral)
Phase Diagrams
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One-component systems: Maximum number of phases at equilibrium = 3.
- (ice, water, vapor): p = 3, C = 1, F = 0 → Invariant (e.g., triple point of water)
- (solid, liquid, gas): p = 3, C = 1, F = 0
- (solid, liquid): p = 2, C = 1, F = 1
- (solid): p = 1, C = 1, F = 2
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Two-component systems: Maximum number of phases at equilibrium = 4
- F = C – P + 2
- Fmax is 3
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Phase diagram of water:
- The diagram shows the stable phases of water at various temperatures and pressures.
- Three areas within the diagram correspond to regions where either water (liquid), ice (solid), or ice (vapor) is the stable phase at a particular pressure and temperature.
- Critical point is shown on the diagram
- The diagram shows the stable phases of water at various temperatures and pressures.
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Phase diagram for CO₂ shows three-phase equilibrium
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Phase diagram for sulphur: shows various transitions between rhombic, monoclinic forms .
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Eutectic system: A system containing two or more components whose melting point is lower than that of either component alone. - A typical eutectic system shows a minimum in the melting/freezing temperature.
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