A saturated solution of sucrose is prepared at 30°C. It is then placed in a refrigerator at 4°C. How much solid sucrose would you expect to find crystallised in the container?
The answer is approxmately 28 can you explain why
This phenomenon is known as recrystallization. The solubility of most solid solutes in a liquid solvent decreases as the temperature decreases. In this case, as the saturated solution of sucrose is cooled from 30°C to 4°C, the solubility of sucrose decreases.
As a result, the excess sucrose in the solution that cannot remain dissolved at 4°C begins to crystallize. The crystallized sucrose forms solid particles or crystals that can be observed in the container.
The approximate value of 28 represents the amount of sucrose that has crystallized out of the solution. It is an estimation based on the decrease in solubility of sucrose at lower temperatures. The exact amount of crystallized sucrose may vary depending on factors such as the initial concentration of the solution and the cooling rate, but an approximate value of 28 is expected.
To understand why approximately 28 grams of solid sucrose would crystallize out of the saturated solution, we need to consider the concept of solubility.
Solubility is the maximum amount of solute (in this case, sucrose) that can dissolve in a given amount of solvent (in this case, water) at a particular temperature. When a saturated solution is prepared, it means that the maximum amount of sucrose has already dissolved in the water at a certain temperature.
As the temperature decreases (due to placing the solution in a refrigerator), the solubility of most solid solutes, including sucrose, decreases. This is because solubility generally decreases with decreasing temperature.
Therefore, when the saturated solution in this case is cooled to 4°C, the solubility of sucrose decreases, leading to the excess sucrose coming out of the solution as crystals and forming a solid precipitate. This process is known as crystallization.
The amount of solid sucrose that would crystallize out can be estimated by calculating the difference between the amount of sucrose that was dissolved in the saturated solution at 30°C and the amount that remains dissolved at 4°C.
Let's assume that initially, 100 grams of sucrose was dissolved in the saturated solution at 30°C. At this temperature, the solubility of sucrose is higher, allowing it to dissolve in the water.
Now, when the solution is cooled to 4°C, some of the sucrose will crystallize out of the solution because it exceeds the solubility limit at this lower temperature.
To approximate the amount of crystallized sucrose, we need to determine the solubility of sucrose at 4°C. Let's assume it is 350 grams of sucrose per liter of water.
If the solution was initially saturated with 100 grams of sucrose, we can calculate the remaining dissolved sucrose at 4°C by subtracting the solubility of sucrose at 4°C (350 grams) from the initial amount of sucrose (100 grams).
100 grams - 350 grams = -250 grams
The negative value indicates that the solution is now supersaturated, meaning that more sucrose has crystallized out than can remain dissolved at 4°C.
The approximate amount of solid sucrose that crystallized out would then be the difference between the initial amount and the remaining dissolved amount:
100 grams - (-250 grams) = 350 grams
Therefore, approximately 350 grams of solid sucrose would be expected to crystallize out of the saturated solution at 4°C.
It is important to note that the actual amount of crystallized sucrose may vary depending on factors such as the purity of the sucrose, the rate of cooling, and other conditions. The calculation above is a simplified estimation for illustrative purposes.