Question

Calculate the change in freezing point when 116.8 grams of barium chloride are added to 250 grams of water. Kf = 1.86°C/m; Kb = 0.512°C/m


-4.17°C

-12.5°C

-8.35°C

0°C

Answer 1

Freezing Point depression formula,

\[\Delta T = i K_f m\]

where,

ΔT = is the change in temperature in kelvin
= New Freezing Temperature - Old Freezing temperature (water freezes at 0 degrees C)
i = the number of molecules or ions.

For example,
-So if you add sugar or any other molecule i = 1,
-If you have KCl you have i=2 because it K dissociates into two ions
-If you add CaCl2, i=3 because it dissociates into 3 ions

Kf is a constant and its value is dependent on the solvent since the solve is water
Kf = -1.858 °C·kg/mol

m = the molality

molality = moles/kg of solvent

They are asking for the change in freezing point so they just want the value ΔT

Answer 2

Hope this helps

Answer 3

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