A 28.4288 g sample of impure magnesium car-
bonate was heated to complete decomposition
according to the equation
MgCO3(s) ! MgO(s) + CO2(g) .
After the reaction was complete, the solid
residue (consisting of MgO and the original
impurities) had a mass of 16.0467 g. Assum-
ing that only the magnesium carbonate had
decomposed, how much magnesium carbon-
ate was present in the original sample?
Answer in units of g
008 10.0 points
The reaction of 8.2 grams of fl
MgCO3 ==> MgO + CO2
loss in mass = mass CO2
Convert mass CO2 to mass MgCO3.
mass CO2 x (molar mass MgCO3/molar mass CO2) = mass MgCO3 in grams.
To answer this question, we need to calculate the mass of magnesium carbonate in the original sample.
First, we need to determine the mass of magnesium carbonate that decomposed. This can be done by subtracting the mass of the residue from the initial mass of the sample:
Mass of decomposed magnesium carbonate = Initial mass - Mass of residue
Initial mass = 28.4288 g
Mass of residue = 16.0467 g
Mass of decomposed magnesium carbonate = 28.4288 g - 16.0467 g
Next, we need to determine the molar mass of magnesium carbonate (MgCO3) to convert the mass to moles. The molar mass of MgCO3 can be calculated by adding the atomic masses of its constituent elements:
Molar mass of MgCO3 = (atomic mass of Mg) + (atomic mass of C) + 3*(atomic mass of O)
The atomic masses of Mg, C, and O can be found in the periodic table:
- Atomic mass of Mg = 24.31 g/mol
- Atomic mass of C = 12.01 g/mol
- Atomic mass of O = 16.00 g/mol
Molar mass of MgCO3 = (24.31 g/mol) + (12.01 g/mol) + 3*(16.00 g/mol)
Next, we can calculate the number of moles of decomposed magnesium carbonate:
Number of moles = Mass / Molar mass
Number of moles of decomposed magnesium carbonate = (Mass of decomposed magnesium carbonate) / (Molar mass of MgCO3)
Finally, we can convert the number of moles of decomposed magnesium carbonate to grams by multiplying by the molar mass:
Mass of magnesium carbonate in the original sample = Number of moles of decomposed magnesium carbonate * Molar mass of MgCO3
Now let's calculate:
Mass of decomposed magnesium carbonate = 28.4288 g - 16.0467 g
Mass of decomposed magnesium carbonate = 12.3821 g
Molar mass of MgCO3 = (24.31 g/mol) + (12.01 g/mol) + 3*(16.00 g/mol)
Molar mass of MgCO3 = 84.32 g/mol
Number of moles of decomposed magnesium carbonate = 12.3821 g / 84.32 g/mol
Mass of magnesium carbonate in the original sample = Number of moles of decomposed magnesium carbonate * Molar mass of MgCO3 = (12.3821 g / 84.32 g/mol) * 84.32 g/mol
Mass of magnesium carbonate in the original sample = 12.3821 g
Therefore, there was 12.3821 g of magnesium carbonate in the original sample.