The boiling point elevation constant, denoted as $K_b$, is a proportionality constant used to quantify the increase in boiling point of a solvent when a solute is added. It has units of degrees Celsius per molal ($\text{°C/m}$).
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$K_b$ is specific to each solvent and must be determined experimentally.
The boiling point elevation can be calculated using the formula $\Delta T_b = K_b \cdot m$, where $m$ is the molality of the solution.
Boiling point elevation is a colligative property, meaning it depends on the number of solute particles, not their identity.
$K_b$ values for common solvents like water are often provided in textbooks or reference materials.
Boiling point elevation occurs because the addition of a non-volatile solute lowers the vapor pressure of the solution.
Review Questions
What does the boiling point elevation constant ($K_b$) represent?
How do you calculate the change in boiling point for a solution using $K_b$?
Why is boiling point elevation considered a colligative property?
Related terms
Molality: A measure of solute concentration defined as moles of solute per kilogram of solvent.
Colligative Properties: Properties that depend on the number of solute particles in a solution, such as boiling point elevation and freezing point depression.
Vapor Pressure: The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature.