in presence of which one of the following chemical hydrous mgcl2 on heating converted to anhydrous mgcl2 1.nacl 2.kcl 3.hcl 4.mg(oh)cl

in presence of which one of the following chemical hydrous mgcl2 on heating converted to anhydrous mgcl2
1.nacl 2.kcl 3.hcl 4.mg(oh)cl

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