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Recrystallization by cooling

Cool the hot solution and look at the moving point of the solubility curve and the precipitated mass.

    C07 · Recrystallization by coolingReady
    Cool the hot solution and look at the moving point of the solubility curve and the precipitated mass. You can also experiment with the numbers and controls below.

    Chemistry · Solution · Solubility / Principles and Exploration

    Recrystallization by cooling — principles and investigation

    When a solute dissolved in hot water is cooled, some of it may come out as crystals due to changes in solubility. Compare the amount of crystals by changing the starting and ending temperatures, mass of water, and amount of solute initially dissolved. Read it based on conservation of mass, which states that the total solute initially added is divided into solutes in solution and crystals.

    How does it work?

    Total solute = dissolved solute + crystal is preserved. If you added less than the dissolution limit at the end temperature, the amount of precipitation is 0 g.

    Key relationship

    Precipitation amount = max(0, m₀ − S(T end) × water mass/100)

    Try this investigation

    1. First, determine the conditions under which all solutes will melt at the starting temperature. With the cooling run, observe the current temperature point on the curve and the change in crystal mass.
    2. Run and record 150 g of virtual A, 100 g of water, starting at 80 °C and ending at 20 °C and 40 °C, respectively.
    3. Compare the conditions in which only water is increased to 200 g, the 38 g condition in virtual B, and the 20 g condition in A that is unsaturated all the way.

    Interpreting your results

    What is the formula for calculating the amount of precipitation when cooling without evaporation or loss?

    Only the amount that can be dissolved at the final temperature remains in the solution. More solutes than that come out as crystals.

    Assumptions and limitations

    This is an educational table of virtual substances A and B. This is not actual reagent data. Assuming 0~100 °C, 1 atm, the unit is g/100 g of water, and linear interpolation is performed between sections. Only run solutions that are fully dissolved at the start. It is a constant water mass/equilibrium cooling model and omits evaporation, nucleation, supersaturation, growth rate, and filtration loss. The cooling time on the screen is a representation and is not a prediction of actual cooling speed or recovery rate.