Dissolved 0.7500 g calcium chloride dihydrate and impure, in distilled water and the volume was elevated to 200.00 mL in a volumetric flask. A rate of 10.00 mL of the same consumed the titration 18.9 mL 0.0125 M EDTA using CALCON as indicator. What is the purity of the salt (% w/w)
To determine the purity of the calcium chloride dihydrate, you need to calculate the amount of calcium chloride present in the 10.00 mL of the solution used for the titration.
First, let's calculate the amount of EDTA used in the titration:
Amount of EDTA (mol) = concentration of EDTA (mol/L) x volume of EDTA used (L)
Amount of EDTA = 0.0125 M x 0.0189 L
Amount of EDTA = 0.00023625 mol
Since the stoichiometric ratio between calcium chloride and EDTA is 1:2 (1 mol of calcium chloride reacts with 2 mol of EDTA), you can calculate the amount of calcium chloride present in the 10.00 mL of solution:
Amount of calcium chloride (mol) = Amount of EDTA (mol) / 2
Amount of calcium chloride = 0.00023625 mol / 2
Amount of calcium chloride = 0.000118125 mol
Now, let's calculate the molar mass of calcium chloride dihydrate:
Molar mass of calcium chloride dihydrate (g/mol) = (molar mass of calcium + 2 x molar mass of chlorine + 2 x molar mass of water)
Molar mass of calcium chloride dihydrate = (40.08 g/mol + 2 x 35.45 g/mol + 2 x 18.015 g/mol)
Molar mass of calcium chloride dihydrate = 110.984 g/mol
Next, we can calculate the mass of calcium chloride present in the 10.00 mL of solution:
Mass of calcium chloride (g) = Amount of calcium chloride (mol) x molar mass of calcium chloride dihydrate (g/mol)
Mass of calcium chloride = 0.000118125 mol x 110.984 g/mol
Mass of calcium chloride = 0.0131089 g
The mass of the impure calcium chloride dihydrate which was dissolved in the 200.00 mL solution is given as 0.7500 g.
Finally, we can calculate the purity of the salt (% w/w):
Purity (%) = (Mass of calcium chloride / Mass of impure calcium chloride) x 100
Purity = (0.0131089 g / 0.7500 g) x 100
Purity = 1.75%
Therefore, the purity of the salt is 1.75% w/w.