Which of the following aqueous solutions has the highest electrical conductivity, assuming equal molar concentrations of 0.10 M?
Show the answer and explanation
Correct answer
D. Calcium chloride (CaCl2)
Principle or equation
Electrical conductivity of a solution depends on the concentration and charge of ions. Strong electrolytes dissociate completely, producing more ions per formula unit. The higher the total ion concentration, the greater the conductivity.
Why this answer is correct
Sucrose is a nonelectrolyte and does not produce ions. Acetic acid is a weak electrolyte, partially ionizing to produce few ions. NaCl is a strong electrolyte producing 2 ions per formula unit (Na+ and Cl-). CaCl2 is a strong electrolyte producing 3 ions per formula unit (Ca2+ and 2 Cl-). At equal molar concentrations, CaCl2 gives the highest total ion concentration (0.30 M ions) and thus the highest conductivity.
Example
0.10 M NaCl has 0.20 M ions, while 0.10 M CaCl2 has 0.30 M ions, so CaCl2 conducts better.
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