A mixture of magnesium carbonate and magnesium oxide of mass #12.46*g# underwent fierce heating. After heating, there were #8.43*g# of salt remaining. What were the masses of magnesium carbonate, and magnesium oxide in the original sample?

1 Answer
May 19, 2017

Answer:

Well, we use the general decomposition #("calcining")# reaction of metal carbonates.............

Explanation:

#MgCO_3(s)+DeltararrMgO(s) + CO_2(g)#

And we would have to heat the magnesium salt VERY fiercely to get complete decarboxylation.

#"Moles of carbon dioxide LOST"# #=# #(4.40*g)/(44.01*g*mol^-1)#

#=0.010*mol#

And therefore in the original mixture there were #0.010*mol# #MgCO_3#, i.e. a mass of #0.010*molxx84.31*g=8.43*g#.

The balance of the salt must have #MgO#, which is (reasonably) inert to heating.

#"Mass of MgO"# #=# #12.46*g-8.43*g=4.03*g#.