A supersaturated solution of sucrose (C₁₂H₂₂O₁₁) is made by dissolving sucrose in hot water and slowly letting the solution cool to room temperature. After a long time, the excess sucrose crystallizes out of the solution. Indicate whether each of the following statements is true or false: (b) After the excess sucrose has crystallized out, the system is now unstable and is not in equilibrium.

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Understand the concept of a supersaturated solution: A supersaturated solution contains more solute than can be dissolved by the solvent under normal circumstances. It is created by dissolving solute at a high temperature and then cooling the solution slowly.

Recognize that when a supersaturated solution is allowed to cool, it can remain in a metastable state until a disturbance causes the excess solute to crystallize out.

Once the excess solute crystallizes out, the solution reaches a state where the concentration of solute in the solution is at equilibrium with the solid solute.

In equilibrium, the rate of dissolution of the solute equals the rate of crystallization, meaning the system is stable and no net change occurs over time.

Therefore, after the excess sucrose has crystallized out, the system is stable and in equilibrium, making the statement false.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Supersaturated Solutions

A supersaturated solution contains more solute than can typically dissolve at a given temperature. This state is achieved by dissolving the solute in hot solvent and then cooling it slowly. The solution is unstable, as it holds excess solute that can precipitate out, leading to crystallization when disturbed or over time.

Equilibrium in Solutions

A solution is in equilibrium when the rate of solute dissolving equals the rate of solute crystallizing. In a saturated solution, this balance is maintained. However, when excess solute crystallizes out of a supersaturated solution, the system can shift towards a new equilibrium, indicating that the previous state was unstable.

Stability of Chemical Systems

The stability of a chemical system refers to its ability to maintain a state of equilibrium without external influence. In the case of a supersaturated solution, once excess solute crystallizes, the system is no longer in its previous unstable state and must adjust to reach a new equilibrium, which may be more stable.

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