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According to me, Mg will be more hydrated and so should have lesser conductivity. Is that correct?

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closed as unclear what you're asking by Jon Custer, Ivan Neretin, Mathew Mahindaratne, Mithoron, A.K. Sep 5 at 17:47

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  • $\begingroup$ The 'hydration' makes this question very unclear. $\endgroup$ – Jon Custer Sep 5 at 13:31
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    $\begingroup$ This question needs to be fixed: neither carbonate is soluble in water and neither melts without decomposition to the respective oxide. If the question is about transport coefficients or whatever, it should ask that. Otherwise, the question should be on hold or closed. $\endgroup$ – Ed V Sep 5 at 13:41
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    $\begingroup$ "Molten solution" is a contradiction in terms. $\endgroup$ – Ivan Neretin Sep 5 at 13:53
  • $\begingroup$ @EdV - but they do melt, just not at STP in air. For example geochemicalperspectivesletters.org/documents/GPL1813_noSI.pdf - Properties of molten CaCO3 at high pressure - important in earth sciences. $\endgroup$ – Jon Custer Sep 5 at 14:23
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    $\begingroup$ @JonCuster Quite honestly, do you really think this is what the question is about? The OP should replace this with a well-formed question and title. Otherwise, it is just leading to non-productive mind reading. $\endgroup$ – Ed V Sep 5 at 14:30
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Do you really think molten inorganic salts will have a trace of water? Second question is do these carbonates melt? Don't mix molten state with aqueous state. No correlation.

When these compounds are heated both MgO and CaO are formed releasing carbon dioxide. They don't like to melt at all. Have you heard of limelight? This comes from CaO glowing brightly at high temperatures.

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  • $\begingroup$ And the connection of this answer to conductivity is what, exactly? $\endgroup$ – Jon Custer Sep 5 at 13:12
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    $\begingroup$ The answer is basically reductio ad absurdum of the original query of molten calcium carbonate and magnesium carbonate. If someone can actually melt them without decomposition, then they should enlighten us. If molten means aqueous state, then it is another story. $\endgroup$ – M. Farooq Sep 5 at 13:18
  • $\begingroup$ You are thinking too narrowly, seemingly limiting your response to STP in air. $\endgroup$ – Jon Custer Sep 5 at 13:20
  • $\begingroup$ Consider papers such as electrochemsci.org/abstracts/vol13/131009771.pdf titled "Effect of Temperature and Voltage on the Preparation of Solid Carbon by Electrolysis of a Molten CaCO3-Li2CO3-LiCl Electrolyte" $\endgroup$ – Jon Custer Sep 5 at 13:22
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    $\begingroup$ Sure, interesting idea but that is a special case when we melt CaCO3 in a certain atmosphere or in the presence of other salts. The OP should clarify the question. It makes no sense as written. "Molten" is not compatible with "hydration." $\endgroup$ – M. Farooq Sep 5 at 13:28
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"Molten" here probably means "liquid". While the carbonates gave too little solubility to be considered for electrolyte, we can compare the conductances of $\ce{Ca^{2+}}$ and $\ce{Mg^{2+}}$ in dilute solution. In this reference from the USGS, conductances from various common ions are given and, indeed, calcium ion has a greater conductance than magnesium ion in solution. But the difference amounts to only a few percent for the overall conductivity of a chloride salt solution at a given concentration.

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