Which of the following compounds would be most effective in lowering the melting point of ice on roads?
A. CaCl2
B. NaCl
C. K3PO4
D. K2SO4
Answer (2)
The compound that would be most effective in lowering the melting point of ice on roads is CaCl2 (calcium chloride). This is because it dissociates into three particles per formula unit when it dissolves in water, according to the principles of colligative properties.
These properties dictate that the freezing point depression is proportional to the number of particles in solution. Calcium chloride will produce one Ca2+ ion and two Cl− ions, for a total of three ions. In comparison, sodium chloride (NaCl) produces only two ions when it dissociates (one Na+ and one Cl−), leading to a smaller depression of the freezing point. More ions mean a larger effect on lowering the freezing point, thereby making CaCl2 more effective for de-icing than NaCl. Potassium phosphate (K3PO4) and potassium sulfate (K2SO4) are not commonly used for de-icing and their ionic dissociations would not be more effective than calcium chloride.
The most effective compound for lowering the melting point of ice on roads is Calcium Chloride (CaCl₂) because it dissociates into three ions, enhancing its freezing point depression effect. While Potassium Phosphate (K₃PO₄) can produce more ions, CaCl₂ is more commonly utilized for road applications due to its effectiveness and lower cost. Therefore, the answer is option A: CaCl₂.
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