Assignment # 02: [CHM 222A & SE331; Part-B]

1. From data given in below table, find activity coefficient at and also find mixG

and mixS when 0.2 mol of acetone (ac) and 0.8 mol of chloroform (cl) are mixed at 308

K, 1 bar pressure.

0.00 0.08 0.20 0.34 0.42 0.51 0.60 0.71 0.81 0.94 1.00

0.00 0.05 0.14 0.32 0.44 0.56 0.69 0.81 0.90 0.97 1.00

P [torr]

293 280 262 249 248 255 267 286 307 332 345

We have discussed this problem during lecture 4 (PrepNotes-4, page 19). The task is to

find out the activity coefficient at , and mixG and mixS.

2. The partial vapor pressure of HCl in liquid GeCl4 are:

0.005 0.012 0.019 32.0 76.9 121.8

(a) Calculate Henrys law constant. (b) Using this data also estimate the partial vapor

pressure of HCl above its solution in liquid GeCl4 of molality 0.1 mol/kg.

3. As we have learned from Lecture-7 that addition of a compound (impurity) to solvent

lowers the freezing point. For suppose addition of 2 grams of a compound to 720 grams

of water lowered the freezing point by 0.12 K. Calculate the molar mass of the

compound using the freezing point constant of water (Kf of water = 1.86 K kg mol-1).

4. The osmotic pressure of an aqueous solution at 288 K is 99 kPa. Calculate the freezing

point of the solution. Consider the aqueous solution as water. Kf of water = 1.86 K kg

mol-1. Use vant Hoff equation.

5. What portions of two ideal solvents should be mixed by mole fraction to achieve the

greatest entropy of mixing?

6. Why do we think the entropy of mixing (mixS) of ideal gases/solutions is not zero? Any

rationale? This is somewhat loaded question, counterintuitive ideas are necessary!

7. Calculate the ionic strength of a solution that is 0.04 mol/kg in aqueous K3[Fe(CN)6], 0.03

mol/kg in aqueous KCl, and 0.05 mol/kg in aqueous NaBr.

8. Using Debye-Hckel limiting law calculate the mean ionic activity coefficient and activity

of NaCl in a solution that is 0.02 mol/kg NaCl and 0.035 mol/kg Ca(NO3)2.