How to Calculate Melting & Boiling Points Using Molality

How to Calculate Melting & Boiling Points Using Molality
••• Magnascan/iStock/GettyImages

In Chemistry, you will often have to perform analyses of solutions. A solution consists of at least one solute dissolving in a solvent. Molality represents the amount of solute in the solvent. As the molality changes, it affects the boiling point and freezing point (also known as the melting point) of the solution. You can easily determine what the boiling or freezing point of any solution will be using a simple equation.

    Note the molality (m) of the solution. A higher molality will increase the boiling point and decrease the freezing point of the solution.

    Use a table to look up the freezing point depression (Kf) or boiling point elevation (Kb) constant for your solvent (See Resources). Every substance has a unique constant that determines how much one mole of solute will decrease the freezing point or increase the boiling point.

    Calculate the change in boiling or freezing temperature using one the following formulas: ΔTf = Kf * m or ΔTb = Kb* m.

    Add the value obtained for ΔTb to the standard boiling point of the solvent (ex. 100 C for water) or subtract the value obtained for ΔTf from the standard freezing point of the solvent (ex. 0 C for water).

    Warnings

    • If the substance ionizes in solution (ex. NaCl), it is necessary to include the Van't Hoff Factor (i). This factor equals the number of ions and is included in the equation as follows: ΔT = Kf * m * i.

Related Articles

How to Calculate the Freezing and Boiling Point
How to Make a Five Percent Solution With Salt
How to Find Y Value for the Slope of a Line
How to Calculate Solubilities
How to Calculate the Freezing and Boiling Point
How to Calculate Moles
How to Calculate Theoretical H3O
How to Find a Z Score
What Color Would a Tester PH Paper Turn if Is Dipped...
How to Dissolve EDTA in Water
How to Change Mixed Fractions to Improper Fractions
How to Do Titration Calculations
Brine Vs. Conductivity
How to Solve a Neutralization Equation
How to Prepare Buffer Solutions
How to Calculate & Mix Chemical Solutions
How to Dissolve Sodium Bicarbonate
Density Vs. Concentration
How to Calculate Ka From Ph

Dont Go!

We Have More Great Sciencing Articles!