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Answer 1 · 2017-05-20T05:18:59

The mass loss must represent #CO_2#; and thus we get #8.43*g# magnesium carbonate, and #6.03*g# #MgO#.

The mass loss must represent #CO_2#. Why? Because carbonates are KNOWN to undergo thermal decomposition according to the following rxn:

#MgCO_3(s) + Delta rarr MgO(s) + CO_2(g)uarr#

And so ..........................

#"moles of carbon dioxide "-=" moles of magnesium carbonate"#

#"Moles of carbon dioxide"=(4.4*g)/(44.01*g*mol^-1)=0.0100*mol#,

which constitutes a mass of #0.0100*molxx84.31*g=8.43*g# WITH RESPECT TO #"magnesium carbonate".#

The balance, #(12.46-8.43)*g=6.03*g# WITH RESPECT TO #"magnesium oxide"#.