Solução saturada, insaturada e supersaturada | Soluções química

Summary

This video explains the three types of solutions: unsaturated, saturated, and supersaturated, focusing on the concept of solubility. An unsaturated solution contains less solute than it can dissolve, while a saturated solution holds the maximum amount of solute at a given temperature, with any excess precipitating out. A supersaturated solution, achieved by heating, contains more solute than normal and is unstable, often leading to the precipitation of excess solute when disturbed. The solubility coefficient, which varies with temperature, is key to understanding these states of solution.

Takeaways

• 😀 The solubility coefficient determines the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.
• 😀 A saturated solution contains the maximum amount of solute that can dissolve at a specific temperature. Any excess solute remains undissolved and forms a precipitate.
• 😀 An unsaturated solution has less solute than the maximum solubility, meaning it can still dissolve more solute.
• 😀 A supersaturated solution holds more solute than what is normally soluble at a given temperature, achieved by heating the solution and then cooling it.
• 😀 Temperature affects solubility: as temperature increases, more solute can often dissolve in the solvent.
• 😀 At 20°C, NaCl can dissolve up to 36g in 100g of water, making a solution saturated if it contains 36g of NaCl.
• 😀 If you add 37g of NaCl at 20°C, 36g will dissolve, and the remaining 1g will precipitate at the bottom, indicating the solution is saturated.
• 😀 When a supersaturated solution is formed, it is unstable and can precipitate excess solute when disturbed.
• 😀 The example of NaCl solubility at 20°C (36g/100g water) and 50°C (37g/100g water) illustrates how solubility changes with temperature.
• 😀 Heating a solution to create a supersaturated solution is a temporary process; once the solution cools, the solute may precipitate back out.
• 😀 A supersaturated solution is highly unstable and requires careful handling to prevent the excess solute from crystallizing out.

Q & A

What is the difference between an unsaturated, saturated, and supersaturated solution?

An unsaturated solution contains less solute than the solvent can dissolve at a given temperature. A saturated solution has the maximum amount of solute that can dissolve at a given temperature, with any excess solute remaining undissolved at the bottom. A supersaturated solution contains more solute than the solvent can normally dissolve at a given temperature, often achieved by heating and then carefully cooling the solution.

What is the coefficient of solubility?

The coefficient of solubility is the amount of solute that can dissolve in a specific amount of solvent at a certain temperature. It defines how much of a substance can be dissolved in a solvent under given conditions.

How much NaCl can dissolve in 100g of water at 20°C?

At 20°C, the solubility of NaCl (salt) is 36g per 100g of water.

What defines an unsaturated solution?

An unsaturated solution contains less solute than the solvent can dissolve at the given temperature. For example, if only 30g of NaCl is added to 100g of water at 20°C, it would be unsaturated because it can still dissolve up to 36g.

What happens in a saturated solution?

In a saturated solution, the solvent has dissolved as much solute as it can at the given temperature. Any additional solute will not dissolve and will remain as a precipitate at the bottom of the solution. For example, if 37g of NaCl is added to 100g of water at 20°C, only 36g will dissolve, and 1g will precipitate.

What is a precipitate in the context of solutions?

A precipitate is the undissolved solute that forms and settles at the bottom of a saturated solution when no more solute can dissolve in the solvent.

How is a supersaturated solution created?

A supersaturated solution is created by dissolving more solute in a solvent than it would normally dissolve at a given temperature. This is usually achieved by heating the solution to increase solubility, then carefully cooling it so the excess solute remains dissolved.

Why is a supersaturated solution unstable?

A supersaturated solution is unstable because it contains more solute than the solvent can normally hold at the given temperature. Any disturbance or change in conditions can cause the excess solute to crystallize out of the solution, returning it to a saturated state.

What temperature is used for the NaCl solubility example in the transcript?

In the transcript, the temperature used for the NaCl solubility examples is 20°C, though it is also mentioned that the solubility of NaCl increases at higher temperatures, such as 50°C.

What happens if a supersaturated solution is disturbed?

If a supersaturated solution is disturbed, the excess solute may rapidly crystallize or precipitate out of the solution, returning it to a saturated state. This can happen with even a slight change in temperature or physical disturbance.