Which of the following solutions has the highest electrical conductivity, assuming equal molar concentrations?
Show the answer and explanation
Correct answer
C. 0.1 M CaCl2
Principle or equation
Electrical conductivity of a solution depends on the total concentration of ions. Strong electrolytes dissociate completely, and the number of ions per formula unit matters. CaCl2 produces three ions per formula unit (Ca2+ and two Cl-), more than NaCl (two ions) or CH3COOH (weak electrolyte, few ions). Glucose is a non-electrolyte.
Why this answer is correct
For 0.1 M solutions, the ion concentration is approximately: CH3COOH: low due to weak dissociation; NaCl: 0.2 M ions; CaCl2: 0.3 M ions; glucose: 0. Thus CaCl2 has the highest ion concentration and highest conductivity.
Example
Compare 0.1 M NaCl (0.2 M ions) and 0.1 M CaCl2 (0.3 M ions). The higher ion concentration gives higher conductivity.
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