Why is calcium chloride (rock salt, CaCl2) more effective than sodium chloride (table salt, NaCl) at de-icing roads in the winter? A. Calcium chloride only breaks into 2 ions, while sodium chloride does not break up and remains 1 ion. B. Calcium is a larger molecule than sodium, so it has a greater effect. C. The additional chlorine atom forms a stronger bond between the atoms in calcium chloride than in sodium chloride, so calcium chloride remains one molecule while sodium chloride breaks apart. D. Calcium chloride breaks into 3 ions, while sodium chloride only breaks into 2 ions.

The correct option is;

D. Calcium chloride breaks into 3 ions, while sodium chloride only breaks into 2 ions

Explanation:

To help melt the ice on icy streets, calcium chloride (CaCl₂) is a more preferred salt type to sodium chloride (NaCl) as when it dissociates into ions in the ice, it forms three ions: a calcium ion, Ca²⁺, and two chloride ions, 2 Cl⁻, while sodium chloride forms two ions: one sodium ion, Na⁺, and one chloride ion, Cl⁻

According to the freezing point depression equation, we have;

ΔT = × m × i

Where;

ΔT = Change in freezing point temperature

= The freezing point depression constant

m = The solution's molality

i = van't Hoff factor

The calcium chloride salt will cause the most depression because the van't Hoff factor is 3 for calcium chloride and 2 for sodium chloride.