In one of the topics related to diffusion of brine water with fresh water during well drilling operation I have come across the statement that “chloride ions are more mobile than sodium ions”. Why is that? Is it related to how H2O molecules attach to the ions?
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In: Chemistry
The ions have the same magnitude of charge but they’re not the same size. The chloride ion is nearly 50% larger than the sodium ion, and this holds the water molecules at a greater distance.
With equal charge but greater distance, the bond is weaker and chloride ions don’t get so bogged down by a gaggle of water molecule clingers that obstruct flow.
While counter-intuitive, the massive Cesium ion is *more* mobile than a tiny Lithium ion in solution because the small ion gets so packed up with clingy water molecules stuck to the high charge density.
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