Dolomite is a mixed carbonate of calcium and magnesium that decomposes to co2 and the metal oxides mgo and cao upon heating. when 15.42 g of dolomite is heated, 7.85 g of mgo and cao are produced. what is percent by mass of mgco3 in the original sample of dolomite?

47%

Explanation:

MgCO₃ (s) → MgO (s) + CO₂ (g)

CaCO₃ (s) → CaO (s) + CO₂ (g)

MgCO₃ (s) + CaCO₃ (s) → MgO (s) + CaO (s) + 2CO₂ (g)

MgO: 40.3044 g/mol

MgCO₃: 84.3139 g/mol

CaO:56.0774 g/mol

CaCO₃: 100.0869 g/mol

CO₂: 44.01 g/mol

15.42 g is the total mass of dolomite.

7.85 g is the sum of MgO and CaO produced.

This means that 7.57 g of CO₂ were produced.

44.01 g CO₂ 1 mol

7.57 g CO₂  x

x = 0.172 mol CO₂

Considering the global reaction, we had 0.172/2 = 0.086 mol of MgCO₃ in the original sample.

1 mol MgCO₃ 84.3139 g

0.086 mol MgCO₃ ___ y

y = 7.25 g

15.42 g dolomite 100%

7.25 g MgCO₃ z

z = 47%

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