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Reviewed CSCA Chemistry question · Hard

Which of the following 0.10 M aqueous solutions will have the highest electrical conductivity? Assume complete dissociation for strong electrolytes.

  1. Sucrose, C12H22O11
  2. Acetic acid, CH3COOH
  3. Calcium chloride, CaCl2
  4. Methanol, CH3OH
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Correct answer

C. Calcium chloride, CaCl2

Principle or equation

Electrical conductivity of a solution depends on the concentration of ions. Strong electrolytes dissociate completely; the more ions produced per formula unit, the higher the conductivity.

Why this answer is correct

CaCl2 dissociates into 3 ions (Ca2+ and 2 Cl-) per formula unit, giving 0.30 M ions. Acetic acid is a weak electrolyte (few ions). Sucrose and methanol are non-electrolytes (no ions). Thus CaCl2 has the highest conductivity.

Example

0.10 M CaCl2 → 0.10 M Ca2+ + 0.20 M Cl- = 0.30 M total ions; others produce fewer or no ions.

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