Which has a higher freezing point calcium chloride or sodium chloride?

Answer 1

Answer: corrected CaCl2 melting point:

772 °C (anhydrous)

260 °C (monohydrate) 176 °C (dihydrate) 45.5 °C (tetrahydrate) 30 °C (hexahydrate)

NaCl melting point:

801 °C, 1074 K, 1474 °F

Calcium Chloride has a lower freezing point at -29 Deg F.

Sodium Chloride has a low limit of Approx -7De F

This couldn't be the right answer: these salts would have been molten to fluids at room temperature 68 oF !!

Answer 2

NaCl will affect them more than an equal gram amount of CaCl2.

The equations for freezing point depression and boiling point elevation are similar. For purposes of explanation we may look at the simplified equation for melting point depression.

ΔTF = KF · b · i

• ΔTF, the freezing point depression, is defined as TF (pure solvent) - TF (solution).
• KF, the cryoscopic constant, which is dependent on the properties of the solvent, not the solute. Note: When conducting experiments, a higher KF value makes it easier to observe larger drops in the freezing point. For water, KF = 1.853 K·kg/mol.[4]
• b is the molality (mol solute per kg of solvent)
• i is the van 't Hoff factor (number of solute particles per mol, e.g. i = 2 for NaCl, i = 3 for CaCl2).

The question then is whether (moles of solute x van't Hoff factor) is greater for sodium chloride or calcium chloride.

The molecular mass of Sodium Chloride is 58.44 g/mol.

The molecular weight of Calcium Chloride is 110.984 g/mol.

From this we can calculate that

100 g of NaCl = 1.71 moles

100 g of CaCl2 = 0.90 moles

so for NaCl 1.71 x 2 = 3.42 and for CaCl2 0.90 x 3 = 2.70

Even though CaCl2 has a larger van't Hoff factor, its higher molecular weight means it would not depress the melting point as much as an equal weight of NaCl. The mathematics for boiling point elevation are analogous; an equal mass of NaCl will raise the boiling point more than CaCl2

Answer 3

Since calcium chloride is a solid (already frozen) at room temperature and methanol is a liquid at room temperature, methanol has a lower freezing point.