CaCl_2 is often used to melt ice on sidewalks. Could CaCl_2 melt ice at -33 degr

Question

CaCl_2 is often used to melt ice on sidewalks. Could CaCl_2 melt ice at -33 degree C? Assume that the solubility of CaCl_2 at this temperature is 70.1 g CaCl_2/100.0 g of H_2 O and that the van't Hoff factor for a saturated solution of CaCl_2 is i = 2.5. Enter "yes" or "no" in the box below. What is the minimum amount of CaCl_2 that would be required to melt ice on sidewalks at the above temperature? Use 100 g of water as the amount of solvent. You asked to the minimum amount. Although this was the value stated in the question, not minimum amount.

Explanation / Answer

dTf = -i*Kf*m

dT = -2.5*(1.86)*mol solute / kg solvent

mol = mass/MW = 70.1/110.98 = 0.63164 mol

kg solvent = 100 g = 0.1 kg

dT = -2.5*(1.86)*0.63164 /0.1

dTf = -29.37 °C

this will NOT melt at -33°C

B)

find min CaCl2 required:

-33 = -2.5*(1.86)*mol solute / 0.1

solvefor mol solute

mol = 33*0.1/2.5/1.86 = 0.709677 mol of CaCl2

mass = mol*MW= 0.709677*110.98

mass = 78.759 g required

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---