Which of the following aqueous solutions contains the greatest number of ions?

a. 400. ml of 0.10 m nacl;
b. 300. ml of 0.10 m cacl2;
c. 200. ml of 0.10 m fecl3

Answer : The correct option is, (b) 300. mL of 0.10 M CaCl₂

Explanation :

We have to calculate the number of moles of ions for the following aqueous solutions.

(a)  400. mL of 0.10 M NaCl

NaCl dissociates to give 2 moles of ions.

Volume of solution = 400. mL = 0.400 L

Total moles of ion = 0.04 mol × 2 = 0.08 mol

(b)  300. mL of 0.10 M CaCl₂

CaCl₂ dissociates to give 3 moles of ions.

Volume of solution = 300. mL = 0.300 L

Total moles of ion = 0.03 mol × 3 = 0.09 mol

(c)  200. mL of 0.10 M FeCl₃

FeCl₃ dissociates to give 4 moles of ions.

Volume of solution = 200. mL = 0.200 L

Total moles of ion = 0.02 mol × 4 = 0.08 mol

From this we conclude that, aqueous solutions contains the greatest number of ions.

Hence, the correct option is, (b) 300. mL of 0.10 M CaCl₂

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