5.33 g of CrCl3 6H2O, which is a 1 : 3 electrolyte, is dissolved in water and is passed through a cation exchanger. The chloride ions in the eluted solution, on treatment with AgNO3 results in 8.61 g of AgCl. The ratio of moles of complex reacted and moles of AgCl formed is 10-2. (Nearest integer) [Molar mass in g mol-1 Cr : 52, Ag : 108, Cl : 35.5, H : 1, O : 16]
Answer
33
Solution
1 : 3 electrolyte ⇒ all three Cl- are ionisable ⇒ complex is [Cr(H2O)6]Cl3
Molar mass of CrCl3 6H2O = 52 + 3(35.5) + 6(18) = 266.5 g mol-1
Moles of complex = 5.33266.5 = 0.02 mol
On the cation exchanger, [Cr(H2O)6]3+ is held and all the Cl- pass into the eluate:
Ag+ + Cl- AgCl
Molar mass of AgCl = 108 + 35.5 = 143.5 g mol-1
Moles of AgCl = 8.61143.5 = 0.06 mol
∴ Ratio = 0.020.06 = 0.333 = 33.3 × 10-2 ≈ 33 × 10-2
Answer: 33