Which of these aqueous solutions would you expect to be the best conductor of electricity at \(25^{\circ} \mathrm{C} ?\) Explain your answer. (a) \(0.20 \mathrm{M} \mathrm{NaCl}\) (b) \(0.60 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}\) (c) \(0.25 M \mathrm{HCl}\) (d) \(0.20 M \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\)

Firstly, check the substances given: (a) \(0.20 \mathrm{M} \mathrm{NaCl}\) is a strong electrolyte and it will completely dissociate into \(\mathrm{Na^{+}}\) and \(\mathrm{Cl^{-}}\) ions, thus producing 2 ions in the solution. (b) \(0.60 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}\) is a weak electrolyte, will partially ionize and produce less number of ions than in the (a) solution, although its molarity is higher. (c) \(0.25 M \mathrm{HCl}\) is a strong electrolyte and will completely dissociate into \(\mathrm{H^{+}}\) and \(\mathrm{Cl^{-}}\) ions, thus producing 2 ions in the solution. (d) \(0.20 M \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\) will dissociate into one \(\mathrm{Mg^{2+}}\) ion and two \(\mathrm{NO_{3}^{-}}\) ions, thus producing 3 ions in solution.

The molar concentration does not change for weak and strong electrolytes but the number of ions in solution does. We can see that solution (a), (c) yields 2 ions per molecule while solution (d) yields 3 ions per molecule. Clearly, solution (d) \(0.20 M \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\) will contain more ions because it ionizes to produce 3 ions per molecule.

Even though solutions (a) and (c) are strong electrolytes, and (b) has a higher molarity but is a weak electrolyte, the solution (d) \(0.20 M \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}\) appears to be the best conductor of electricity, as it produces the highest number of ions in the solution when compared to other given solutions.