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    Hello, the question states that " when solid samples of sodium carbonate and magnesium carbonates are strongly heated" (answer) MgCO3 decomposes but sodium carbonate does not??????? can someone explain to me why that is correct

    another 1....
    "The best way to confirm for the presence of iodine in an aqueous solution is"- adding hexane to form a purple layer is the answer, but adding acidifies AgNO3 to form a yellow ppt which is insoluble in conc. ammonia isnt the right answer...!!
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    (Original post by DrTK278)
    Hello, the question states that " when solid samples of sodium carbonate and magnesium carbonates are strongly heated" (answer) MgCO3 decomposes but sodium carbonate does not??????? can someone explain to me why that is correct

    another 1....
    "The best way to confirm for the presence of iodine in an aqueous solution is"- adding hexane to form a purple layer is the answer, but adding acidifies AgNO3 to form a yellow ppt which is insoluble in conc. ammonia isnt the right answer...!!
    1) Yes, you get ionic interactions between positive metal ions and negative carbonate ions. but you should be aware of the covalent bonding within the carbonate ion itself. Charge of cations (metallic species) present polarises the electron density in the carbonate ion(the covalent part).

    Higher charged Mg2+ in the same period as Na+ is more polarising, carbonate polarised more by Mg2+, CO2 can break off and form "more easily" - reactions happen because of the favourable energetics (overall)

    2) AgNO3 forms the yellow precipitate with iodide salt - that yellow ppt is AgI. You use ammonia to distinguish AgI with creamy AgBr which dissolves in conc ammonia. Depending on concentration, sometimes colour of AgBr and AgI can be quite difficult to distinguish.

    Iodine is a non polar molecule, hence it does not mix with water. it is however soluble in non polar solvent (just like oils are hydrocarbons mostly and they mix with organic solvents which tend to be non polar too).

    so i'd say iodine, iodide are different - that is perhaps your problem
 
 
 
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