what would the molarity of a pure solute be?? (Magnesium chloride specifically)
I don't know that it has one (but see the later link). Molarity is defined as number of moles/L of solution. The number of moles can be calculated easily but since there is no solvent I don't see how a molarity can be calculated. However, here is a link that uses that expression and talks about a more appropriate name for it.
https://chemistrygod.com/molarity-of-pure-substances