Question

Only number 3.

Water IN LAB QUESTIONs: What is the actual freezing point depression of your anti-freeze? Therefore, what is the experimental van't Hoff factor of your solute? How much would it cost to make 2 L of your anti-freeze? POST LAB QUESTIONS 2. Using the knowledge you have gained, determine which of the above solutes would make the best anti-freeze. The best anti-freeze will be a soluble solution, which gives a 20 degree change in freezing point (use experimental van't Hoff) and will be the most cost effective. Build a table showing the amounts of solute and solvent needed to make that anti-freeze and the cost to make 2 L of that anti-freeze. NOTE: The anti-freeze you made in lab may not have had a 20 degree change due to pairing of ions. 3. Determine the amounts of solute needed to make 100 mL aqueous solutions of NaCI and MgCl2 that will cause a 10 degree change in freezing point. Determine the amounts of solute 9 needed to make 100 mL aqueous solutions of AICls and ethanol (or ethylene glycol) that will cause a 10 degree change in boiling point.

Answer 1

We know M_2 = k_f times W_2 times 1000/W_1 times Delta T_f M_2 = molar mass of solute W_2 = weight of solute K_f = cryseopic constant of solvent W_1 = weight of solvent Delta T_f = change of freezing point For Nacl Here M_2(Nacl) = 58.439 K_f(H_2 O) = 1.86 K gmol^-1 W_2 = ? W_1 = 100 gm Delta T_f = 10 degrees W_2 = 58.439 times 100 times 10/1.86 times 1000 = 31.419 gm For MgCl_2 M_2 = 95.205 N_1 = 100gm W_2 =/ K_f(H_2 O) = 1.86 KKg mol^-1 Delta T_f = 10 degrees W_2 = 95.205 times 100 times 10/1.86 times 1000 = 51.185 gm