Question

2. When 40.7 g of the "salt" HgCl is dissolved in 100 g water, the freezing point depression is observed to be 2.83 K. Based on this, does one expect the solution to readily conduct electricity? 3. What are the solvent and solute activities and activity coefficients for a component having 25% mole fraction and obeying the vapor pressure equation P, = 78.8x, (0.65x4+0.18x)? (Hint: think about Raoult's and Henry's Laws) 4. The Debye-Huckel limiting law is strictly valid only in the limit of infinite dilution. A more widely applicable equation is the Debye-Huckel equation: 0.51012.2.1 logy+ = - 1 + (0.328a/T) This equation applies at 25 °C in dilute aqueous solution. a. For a 0.00100 m aqueous solution of CaCl2 at 25 °C, the Y+ is found experimentally to equal 0.888. Use this to determine the value of the constant a (which is related to the ion size and has units of A). b. Use the value of a from part a. to estimate Y+ for a 0.0100 m aqueous CaCl2 solution at 25°C.

Answer 1

According to HOMEWORKLIB RULES we have to answer only first one problem

The freezing point depression is given by:

T = k b i

Where:

T = freezing point depression , 2.83 K

k = cryoscopic constant ;1.853 °K /m

The K_f for water is 1.853 K·kg/mol
b = molality (moles of solute per kg of solvent)
i = van't Hoff factor, r

Number of moles = amount in g / molar mass

= 40.7 g/ 271.52 g/mol

=0.1499 moles

Mass of water = 100 g or 0.100 kg

Molality = number of moles / solvent in kg

=> m =0.1499 moles /0.100 kg

= 1.499 m

Therefore calculate the i as follows:

T = k b i

2.83 K = 1.853 °K /m*1.499 m *i

i = 1.0

the value of i is 1 means it is not ionize thus it is an example of weak electrolyte which will not conduct electricity

there is no ions

Weak electrolytes:

Weak electrolytes are partially ionizes in water.

Strong electrolytes have following properties:

1. They are ionic compounds.
2. They are completely separates into their ions when dissolved in water.
3. In solution form they conduct electricity due to present of ions but in solid form means neutral molecule does not conduct electricity.