Animated Solution for Chemistry - Electrochemistry: Amongst the following, the form of water with the lowest ionic conductance at 298 K is

When we talk about the ability of a liquid to conduct electricity, we are stepping into the fascinating world of electrochemistry. Unlike metals, where free electrons carry the current, liquids rely on a different mechanism. In aqueous solutions, electricity is conducted by the movement of charged particles known as ions.

This property is called ionic conductance. The fundamental rule here is beautifully simple: the ionic conductance of a solution is directly proportional to the concentration of free ions present in it.

If a solution is packed with ions, it will be an excellent conductor. Conversely, if a liquid has very few or no ions, it will act as an insulator. With this principle in mind, let's investigate the different forms of water given in our problem to find the one with the lowest ionic conductance.

Let's break down each option based on its chemical composition:

1. Saline Water: Saline water, especially the kind used for intravenous injections, is a carefully prepared solution of sodium chloride ($NaCl$) in water. Sodium chloride is a strong electrolyte. When dissolved, it completely dissociates into sodium ($N{a}^{+}$) and chloride ($C{l}^{-}$) ions. Because it is rich in these free ions, saline water is a very good conductor of electricity.

2. Sea Water: Imagine the vast oceans. Sea water is notoriously salty. It contains a massive concentration of dissolved salts—not just $NaCl$, but also magnesium chloride ($MgC{l}_2$), magnesium sulfate ($MgS{O}_4$), and calcium compounds. This dense soup of ions makes sea water an exceptionally strong conductor.

3. Well Water: Water drawn from a well is essentially groundwater. As rain seeps through the earth's crust, it travels through various layers of soil and rock. During this journey, it dissolves numerous minerals, predominantly calcium and magnesium bicarbonates. These dissolved minerals provide a steady supply of ions, giving well water a significant ionic conductance.

4. Distilled Water: Now, let's look at distilled water. Distillation is a rigorous purification process. Water is heated until it turns into steam, leaving all solid impurities, minerals, and salts behind in the boiling vessel. The pure steam is then captured and cooled back into liquid water. Because all the dissolved salts have been stripped away, distilled water contains virtually zero free ions.

Since ionic conductance is entirely dependent on the presence of free ions, the liquid with the fewest ions will naturally have the lowest conductance.

Distilled water, being the purest form among the choices and lacking dissolved minerals or salts, fits this description perfectly. While it does undergo a microscopic amount of self-ionization (producing a negligible amount of $H^{+}$ and $O{H}^{-}$ ions), its conductance is practically zero compared to the other options.

Therefore, distilled water is the correct answer.