The mineral dolomite has the formula caco3.mgco3. When dolomite is heated for an extended period of time at elevated temperature it decomposed to give carbon dioxide and a mixture of calcium oxide and magnesium oxide. If a 5.424 g sample of the mineral is heated for several hours at 950 degrees celcius. How many grams should the mixed oxide residue remaining weight?

1 answer

As far as I can tell, dolomite is a 50/50 mixture (mostly) of CaCO3 and MgCO3.
CaCO3 ==> CaO + CO2
MgCO3 ==> MgO + CO2

5.424/2 = approx 2.7 g MgCO3 and approx 2.7 g CaCO3.

Starting with these amounts and the equations above, solve for grams CaO and grams MgO, then add those together.
Post your work if you get stuck.