This question concerns boiling point elevation.

Question

Assume you are given 0.040 m solutions in acetic acid of KI, MgCl2, an CaSO4. Determine the expected change to the boiling point of each.

Answer 1

To solve for change in boiling point you would use the equation ΔT_b = K_bmi

ΔT_b is the change in the boiling point

K_b is the boiling point elevation constant

m is the molality

i is the Van't Hoff factor (the number of ions in the dissociating compound)

K_b would most likely be provided in the problem or in a reference table. For acetic acid I believe it is 3.07^oC/m

To solve for KI you would have ΔT_b = 3.07^oC/m x 0.040m x 2 (This is because KI dissociates into two ions. One K⁺ and one I^-) ΔT_b = 0.246^oC

To solve for MgCl₂ you would have ΔT_b = 3.07^oC/m x 0.040m x 3 (This is because MgCl₂ dissociates into three ions. One Mg²⁺ and two Cl^-) ΔT_b = 0.368^oC



To solve for CaSO₄ you would have ΔT_b = 3.07^oC/m x 0.040m x 2 (This is because CaSO₄ dissociates into two ions. One Ca⁺ and one SO₄^2-) ΔT_b = 0.246^oC