Question

You want to purchase a salt to melt snow and ice on your sidewalk. Which one of the following salts would best accomplish your task using the least amount (to reach same freezing point): NaCl or CaCl2?

Answer 1

NaCl.

Explanation:

I'm not entirely sure about the explanation, but what i can tell is that natrium is one of the most reactive elements in chemistry. Even if you place a piece on natrium inside water it will go nuts, start making bubbles and moving pretty fast. Also, im pretty sure most of the people ( and even the companies in charge for this task on the streets ) use NaCl because its more efficient than other compunds ( its not the price factor because salts are cheap ).

So, overall, i think NaCl has more entalpy potential than CaCl2.

Answer 2

Calcium chloride uses the least amount to reach the same freezing point.

Explanation:

Among the factors that affect the effectiveness of a deicer are the

• van't Hoff `i` factor
• enthalpy of solution

The van't Hoff `i` factor

The amount by which a deicer can decrease the freezing point of water `ΔT_text(f)` is directly proportional to the value of `i`.

`i` is the number of ions formed from one formula unit of the salt.

`"NaCl(s)" → "Na"^"+""(aq)" + "Cl"^"-""(aq)"; i = 2`

`"CaCl"_2"(s)" → "Ca"^"2+""(aq)" + "2Cl"^"-""(aq)"; i =3`

Thus, on a molar basis, `"CaCl"_2` is 50 % more efficient than `"NaCl"`.

However, the molar mass of `"CaCl"_2` is 1.9 times that of `"NaCl"`.

On a mass basis, `"CaCl"_2` is only 80 % as efficient as `"NaCl"`.

Enthalpy of solution

As the deicer melts the ice, its ions go into solution.

`"NaCl(s)" → "Na"^"+""(aq)" + "Cl"^"-""(aq)"; Δ_text(fus)H = "+3.9 kJ·mol"^"-1"`

`"CaCl"_2"(s)" → "Ca"^"2+""(aq)" + "2Cl"^"-""(aq)"; Δ_text(fus)H = "-81.3 kJ·mol"^"-1"`

The dissolving of `"NaCl"` is endothermic, but the dissolution of `"CaCl"_2` is exothermic.

This evolution of heat gives calcium chloride its deicing advantage over sodium chloride:

• It melts more ice
• It works faster
• It works at lower temperatures